重新封装waterfall_flow

.gitignore

+# Miscellaneous
+*.class
+*.log
+*.pyc
+*.swp
+.DS_Store
+.atom/
+.buildlog/
+.history
+.svn/
+
+# IntelliJ related
+*.iml
+*.ipr
+*.iws
+.idea/
+
+# The .vscode folder contains launch configuration and tasks you configure in
+# VS Code which you may wish to be included in version control, so this line
+# is commented out by default.
+#.vscode/
+
+# Flutter/Dart/Pub related
+**/doc/api/
+.dart_tool/
+.flutter-plugins
+.packages
+.pub-cache/
+.pub/
+build/
+
+# Android related
+**/android/**/gradle-wrapper.jar
+**/android/.gradle
+**/android/captures/
+**/android/gradlew
+**/android/gradlew.bat
+**/android/local.properties
+**/android/**/GeneratedPluginRegistrant.java
+
+# iOS/XCode related
+**/ios/**/*.mode1v3
+**/ios/**/*.mode2v3
+**/ios/**/*.moved-aside
+**/ios/**/*.pbxuser
+**/ios/**/*.perspectivev3
+**/ios/**/*sync/
+**/ios/**/.sconsign.dblite
+**/ios/**/.tags*
+**/ios/**/.vagrant/
+**/ios/**/DerivedData/
+**/ios/**/Icon?
+**/ios/**/Pods/
+**/ios/**/.symlinks/
+**/ios/**/profile
+**/ios/**/xcuserdata
+**/ios/.generated/
+**/ios/Flutter/App.framework
+**/ios/Flutter/Flutter.framework
+**/ios/Flutter/Flutter.podspec
+**/ios/Flutter/Generated.xcconfig
+**/ios/Flutter/app.flx
+**/ios/Flutter/app.zip
+**/ios/Flutter/flutter_assets/
+**/ios/Flutter/flutter_export_environment.sh
+**/ios/ServiceDefinitions.json
+**/ios/Runner/GeneratedPluginRegistrant.*
+
+# Exceptions to above rules.
+!**/ios/**/default.mode1v3
+!**/ios/**/default.mode2v3
+!**/ios/**/default.pbxuser
+!**/ios/**/default.perspectivev3
+!/packages/flutter_tools/test/data/dart_dependencies_test/**/.packages
+
+.packages
+pubspec.lock
\ No newline at end of file

.metadata

+# This file tracks properties of this Flutter project.
+# Used by Flutter tool to assess capabilities and perform upgrades etc.
+#
+# This file should be version controlled and should not be manually edited.
+
+version:
+  revision: ee032f67c734e607d8ea5c870ba744daf4bf56e7
+  channel: master
+
+project_type: package

.vscode/launch.json

+{
+    // Use IntelliSense to learn about possible attributes.
+    // Hover to view descriptions of existing attributes.
+    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "name": "debug",
+            "request": "launch",
+            "type": "dart",
+            "program": "example/lib/main.dart",
+        }
+    ]
+}
\ No newline at end of file

.vscode/settings.json

+{
+    "dart.flutterSdkPath": "/Users/roott/Documents/Tools/flutter/master",
+    "spellright.language": [
+        "en"
+    ],
+    "spellright.documentTypes": [
+        "markdown",
+        "latex",
+        "plaintext",
+        "dart"
+    ],
+    "spellright.parserByClass": {
+        "dart": {
+            "parser": "code"
+        }
+    }
+}
\ No newline at end of file

CHANGELOG.md

+## 2.0.5
+
+* getter 'minTrailingIndex' was called on null(#18)
+
+## 2.0.4
+
+* keep the trailingChildren around when run out of children before reaching the scroll offset(#14)
+
+## 2.0.3
+
+* fix closeToTrailing issue. extended_list#6
+
+## 2.0.2
+
+* fix wrong layout when child's size is changed.
+
+## 2.0.1
+
+* fix wrong layout when itemCount is changed.(#6)
+
+## 2.0.0
+
+* breaking change: fix typo(fullCrossAxisExtend => fullCrossAxisExtent)
+* breaking change: SliverWaterfallFlowDelegate is replace with SliverWaterfallFlowDelegateWithFixedCrossAxisCount and SliverWaterfallFlowDelegateWithMaxCrossAxisExtent.
+* support WaterfallFlow.count, WaterfallFlow.extend,SliverWaterfallFlow.count,SliverWaterfallFlow.extend.
+
+## 1.0.1
+
+* add miss dragStartBehavior.
+
+## 1.0.0
+
+* fix sdk error.
+* support ScrollViewKeyboardDismissBehavior(breaking change 1.17.0)
+
+## 0.1.5
+
+* fix sdk error.
+
+## 0.1.4
+
+* fix leading items are missing when pull to refresh.
+* fix analysis_options
+
+## 0.1.3
+
+* web support.
+
+## 0.1.2
+
+* update demo.
+
+## 0.1.1
+
+* update description.
+
+# 0.1.0
+
+* first release.

LICENSE

+MIT License
+
+Copyright (c) 2019 zmtzawqlp
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
\ No newline at end of file

README-ZH.md

+# waterfall_flow
+
+
+[![pub package](https://img.shields.io/pub/v/waterfall_flow.svg)](https://pub.dartlang.org/packages/waterfall_flow) [![GitHub stars](https://img.shields.io/github/stars/fluttercandies/waterfall_flow)](https://github.com/fluttercandies/waterfall_flow/stargazers) [![GitHub forks](https://img.shields.io/github/forks/fluttercandies/waterfall_flow)](https://github.com/fluttercandies/waterfall_flow/network)  [![GitHub license](https://img.shields.io/github/license/fluttercandies/waterfall_flow)](https://github.com/fluttercandies/waterfall_flow/blob/master/LICENSE)  [![GitHub issues](https://img.shields.io/github/issues/fluttercandies/waterfall_flow)](https://github.com/fluttercandies/waterfall_flow/issues) <a target="_blank" href="https://jq.qq.com/?_wv=1027&k=5bcc0gy"><img border="0" src="https://pub.idqqimg.com/wpa/images/group.png" alt="flutter-candies" title="flutter-candies"></a>
+
+能够快速构建瀑布流布局的列表.
+
+[Web demo for WaterfallFlow](https://fluttercandies.github.io/waterfall_flow/)
+
+Language: [English](README.md) | 中文简体
+
+- [waterfall_flow](#waterfall_flow)
+  - [使用](#使用)
+  - [简单使用](#简单使用)
+  - [列表元素回收](#列表元素回收)
+  - [ViewportBuilder](#viewportbuilder)
+  - [LastChildLayoutTypeBuilder](#lastchildlayouttypebuilder)
+  - [CloseToTrailing](#closetotrailing)
+
+## 使用
+
+* 在pubspec.yaml中增加库引用
+
+```yaml
+
+dependencies:
+  waterfall_flow: any
+
+```
+* 导入库
+
+```dart
+
+  import 'package:waterfall_flow/waterfall_flow.dart';
+
+```
+
+
+## 简单使用
+
+| ![img](https://github.com/fluttercandies/flutter_candies/tree/master/gif/waterfall_flow/random_sized.gif) | ![img](https://github.com/fluttercandies/flutter_candies/tree/master/gif/waterfall_flow/custom_scrollView.gif) |
+| --------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------- |
+| ![img](https://github.com/fluttercandies/flutter_candies/tree/master/gif/waterfall_flow/known_sized.gif)  | ![img](https://github.com/fluttercandies/flutter_candies/tree/master/gif/waterfall_flow/variable_sized.gif)    |
+
+你可以通过设置SliverWaterfallFlowDelegate参数来定义瀑布流
+
+* SliverWaterfallFlowDelegateWithFixedCrossAxisCount
+
+| 参数      | 描述          | 默认 |
+| -------------- | -------------------- | ------- |
+| crossAxisCount | 横轴的等长度元素数量 | 必填    |
+
+* SliverWaterfallFlowDelegateWithMaxCrossAxisExtent
+
+| 参数          | 描述                                    | 默认  |
+| ------------------ | ---------------------------------------------- | -------- |
+| maxCrossAxisExtent | 横轴元素最大的大小. | required |
+
+* SliverWaterfallFlowDelegate
+
+| 参数          | 描述                                    | 默认  |
+| ------------------ | ---------------------------------------------- | -------- |
+| mainAxisSpacing            | 主轴元素之间的距离                     | 0.0|
+| crossAxisSpacing           | 横轴元素之间的距离                     | 0.0|
+| collectGarbage             | 元素回收时候的回调                     | -  |
+| lastChildLayoutTypeBuilder | 最后一个元素的布局样式(详情请查看后面) | -   |
+| viewportBuilder            | 可视区域中元素indexes变化时的回调      | -   |
+| closeToTrailing            | 可否让布局紧贴trailing(详情请查看后面) | false|
+
+```dart
+            WaterfallFlow.builder(
+              //cacheExtent: 0.0,
+              padding: EdgeInsets.all(5.0),
+              gridDelegate: SliverWaterfallFlowDelegateWithFixedCrossAxisCount(
+                  crossAxisCount: 2,
+                  crossAxisSpacing: 5.0,
+                  mainAxisSpacing: 5.0,
+                  /// follow max child trailing layout offset and layout with full cross axis extend
+                  /// last child as loadmore item/no more item in [GridView] and [WaterfallFlow]
+                  /// with full cross axis extend
+                  //  LastChildLayoutType.fullCrossAxisExtend,
+
+                  /// as foot at trailing and layout with full cross axis extend
+                  /// show no more item at trailing when children are not full of viewport
+                  /// if children is full of viewport, it's the same as fullCrossAxisExtend
+                  //  LastChildLayoutType.foot,
+                  lastChildLayoutTypeBuilder: (index) => index == _list.length
+                      ? LastChildLayoutType.foot
+                      : LastChildLayoutType.none,
+                  ),
+
+```
+
+## 列表元素回收
+
+追踪列表元素回收，你可以在这个时刻回收一些内存，比如图片的内存缓存。
+
+[更多详情](https://github.com/fluttercandies/extended_image/blob/e1577bc4d0b57c725110a9d886703b98a72772b5/example/lib/pages/photo_view_demo.dart#L91)
+
+```dart
+        WaterfallFlow.builder(
+            gridDelegate: SliverWaterfallFlowDelegateWithFixedCrossAxisCount(
+                     collectGarbage: (List<int> garbages) {
+                  ///collectGarbage
+                  garbages.forEach((index) {
+                    final provider = ExtendedNetworkImageProvider(
+                      _list[index].imageUrl,
+                    );
+                    provider.evict();
+                  });
+                },
+              ),
+```
+
+## ViewportBuilder
+
+追踪进入Viewport的列表元素的index（即你看到的可视区域，并不包括缓存距离）
+
+```dart
+        WaterfallFlow.builder(
+            gridDelegate: SliverWaterfallFlowDelegateWithFixedCrossAxisCount(
+                viewportBuilder: (int firstIndex, int lastIndex) {
+                print("viewport : [$firstIndex,$lastIndex]");
+                }),
+```
+
+## LastChildLayoutTypeBuilder
+
+为最后一个元素创建特殊布局，这主要是用在将最后一个元素作为loadmore/no more的时候。
+
+```dart
+        enum LastChildLayoutType {
+        /// 普通的
+        none,
+
+        /// 将最后一个元素绘制在最大主轴Item之后，并且使用横轴大小最为layout size
+        /// 主要使用在[ExtendedGridView] and [WaterfallFlow]中，最后一个元素作为loadmore/no more元素的时候。
+        fullCrossAxisExtend,
+
+        /// 将最后一个child绘制在trailing of viewport，并且使用横轴大小最为layout size
+        /// 这种常用于最后一个元素作为loadmore/no more元素，并且列表元素没有充满整个viewport的时候
+        /// 如果列表元素充满viewport，那么效果跟fullCrossAxisExtend一样
+        foot,
+        }
+
+      WaterfallFlow.builder(
+        gridDelegate: SliverWaterfallFlowDelegateWithFixedCrossAxisCount(
+            lastChildLayoutTypeBuilder: (index) => index == length
+                ? LastChildLayoutType.foot
+                : LastChildLayoutType.none,
+            ),
+```
+
+## CloseToTrailing
+
+当reverse设置为true的时候，布局会变成如下。常用于聊天列表，新的会话会被插入0的位置，但是当会话没有充满viewport的时候，下面的布局不是我们想要的。
+
+```
+     trailing
+-----------------
+|               |
+|               |
+|     item2     |
+|     item1     |
+|     item0     |
+-----------------
+     leading
+```
+
+为了解决这个问题，你可以设置 closeToTrailing 为true, 布局将变成如下
+该属性同时支持[ExtendedGridView],[ExtendedList],[WaterfallFlow]。
+当然如果reverse如果不为ture，你设置这个属性依然会生效，没满viewport的时候布局会紧靠trailing
+
+```
+     trailing
+-----------------
+|     item2     |
+|     item1     |
+|     item0     |
+|               |
+|               |
+-----------------
+     leading
+```
+
+```dart
+      WaterfallFlow.builder(
+        reverse: true,
+        gridDelegate: SliverWaterfallFlowDelegateWithFixedCrossAxisCount(closeToTrailing: true),
+```
+
+## ☕️Buy me a coffee
+
+![img](http://zmtzawqlp.gitee.io/my_images/images/qrcode.png)

README.md

+# waterfall_flow
+
+[![pub package](https://img.shields.io/pub/v/waterfall_flow.svg)](https://pub.dartlang.org/packages/waterfall_flow) [![GitHub stars](https://img.shields.io/github/stars/fluttercandies/waterfall_flow)](https://github.com/fluttercandies/waterfall_flow/stargazers) [![GitHub forks](https://img.shields.io/github/forks/fluttercandies/waterfall_flow)](https://github.com/fluttercandies/waterfall_flow/network)  [![GitHub license](https://img.shields.io/github/license/fluttercandies/waterfall_flow)](https://github.com/fluttercandies/waterfall_flow/blob/master/LICENSE)  [![GitHub issues](https://img.shields.io/github/issues/fluttercandies/waterfall_flow)](https://github.com/fluttercandies/waterfall_flow/issues) <a target="_blank" href="https://jq.qq.com/?_wv=1027&k=5bcc0gy"><img border="0" src="https://pub.idqqimg.com/wpa/images/group.png" alt="flutter-candies" title="flutter-candies"></a>
+
+A Flutter grid view easy to build waterfall flow layout quickly.
+
+[Web demo for WaterfallFlow](https://fluttercandies.github.io/waterfall_flow/)
+
+Language: English | [中文简体](README-ZH.md)
+
+- [waterfall_flow](#waterfall_flow)
+  - [Use](#use)
+  - [Easy to use](#easy-to-use)
+  - [CollectGarbage](#collectgarbage)
+  - [ViewportBuilder](#viewportbuilder)
+  - [LastChildLayoutTypeBuilder](#lastchildlayouttypebuilder)
+  - [CloseToTrailing](#closetotrailing)
+
+## Use
+
+* add library to your pubspec.yaml
+
+```yaml
+
+dependencies:
+  waterfall_flow: any
+
+```
+* import library in dart file
+
+```dart
+
+  import 'package:waterfall_flow/waterfall_flow.dart';
+
+```
+
+
+## Easy to use
+
+| ![img](https://github.com/fluttercandies/flutter_candies/tree/master/gif/waterfall_flow/random_sized.gif) | ![img](https://github.com/fluttercandies/flutter_candies/tree/master/gif/waterfall_flow/custom_scrollView.gif) |
+| --------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------- |
+| ![img](https://github.com/fluttercandies/flutter_candies/tree/master/gif/waterfall_flow/known_sized.gif)  | ![img](https://github.com/fluttercandies/flutter_candies/tree/master/gif/waterfall_flow/variable_sized.gif)    |
+
+you can define waterfall flow layout within SliverWaterfallFlowDelegate.
+
+* SliverWaterfallFlowDelegateWithFixedCrossAxisCount
+
+| parameter      | description                               | default  |
+| -------------- | ----------------------------------------- | -------- |
+| crossAxisCount | The number of children in the cross axis. | required |
+
+* SliverWaterfallFlowDelegateWithMaxCrossAxisExtent
+
+| parameter          | description                                    | default  |
+| ------------------ | ---------------------------------------------- | -------- |
+| maxCrossAxisExtent | The maximum extent of tiles in the cross axis. | required |
+
+* SliverWaterfallFlowDelegate
+
+| parameter          | description                                    | default  |
+| ------------------ | ---------------------------------------------- | -------- |
+| mainAxisSpacing            | The number of logical pixels between each child along the main axis.                | 0.0      |
+| crossAxisSpacing           | The number of logical pixels between each child along the cross axis.               | 0.0      |
+| collectGarbage             | Call when collect garbage, return indexs to collect                                 | -        |
+| lastChildLayoutTypeBuilder | The builder to get layout type of last child ,Notice: it should only for last child | -        |
+| viewportBuilder            | The builder to get indexs in viewport                                               | -        |
+| closeToTrailing            | Whether make layout close to trailing                                               | false    |
+
+```dart
+            WaterfallFlow.builder(
+              //cacheExtent: 0.0,
+              padding: EdgeInsets.all(5.0),
+              gridDelegate: SliverWaterfallFlowDelegateWithFixedCrossAxisCount(
+                  crossAxisCount: 2,
+                  crossAxisSpacing: 5.0,
+                  mainAxisSpacing: 5.0,
+                  /// follow max child trailing layout offset and layout with full cross axis extend
+                  /// last child as loadmore item/no more item in [GridView] and [WaterfallFlow]
+                  /// with full cross axis extend
+                  //  LastChildLayoutType.fullCrossAxisExtend,
+
+                  /// as foot at trailing and layout with full cross axis extend
+                  /// show no more item at trailing when children are not full of viewport
+                  /// if children is full of viewport, it's the same as fullCrossAxisExtend
+                  //  LastChildLayoutType.foot,
+                  lastChildLayoutTypeBuilder: (index) => index == _list.length
+                      ? LastChildLayoutType.foot
+                      : LastChildLayoutType.none,
+                  ),
+
+```
+
+## CollectGarbage
+
+track the indexes are collect, you can collect garbage at that monment(for example Image cache)
+
+[more detail](https://github.com/fluttercandies/extended_image/blob/e1577bc4d0b57c725110a9d886703b98a72772b5/example/lib/pages/photo_view_demo.dart#L91)
+
+```dart
+        WaterfallFlow.builder(
+            gridDelegate: SliverWaterfallFlowDelegateWithFixedCrossAxisCount(
+                collectGarbage: (List<int> garbages) {
+                  ///collectGarbage
+                  garbages.forEach((index) {
+                    final provider = ExtendedNetworkImageProvider(
+                      _list[index].imageUrl,
+                    );
+                    provider.evict();
+                  });
+                },
+              ),
+```
+
+## ViewportBuilder
+
+track the indexes go into the viewport, it's not include cache extent.
+
+```dart
+        WaterfallFlow.builder(
+            gridDelegate: SliverWaterfallFlowDelegateWithFixedCrossAxisCount(
+                viewportBuilder: (int firstIndex, int lastIndex) {
+                print("viewport : [$firstIndex,$lastIndex]");
+                }),
+```
+
+## LastChildLayoutTypeBuilder
+
+build lastChild as special child in the case that it is loadmore/no more item.
+
+```dart
+        enum LastChildLayoutType {
+        /// as default child
+        none,
+
+        /// follow max child trailing layout offset and layout with full cross axis extend
+        /// last child as loadmore item/no more item in [ExtendedGridView] and [WaterfallFlow]
+        /// with full cross axis extend
+        fullCrossAxisExtend,
+
+        /// as foot at trailing and layout with full cross axis extend
+        /// show no more item at trailing when children are not full of viewport
+        /// if children is full of viewport, it's the same as fullCrossAxisExtend
+        foot,
+        }
+
+      WaterfallFlow.builder(
+        gridDelegate: SliverWaterfallFlowDelegateWithFixedCrossAxisCount(
+            lastChildLayoutTypeBuilder: (index) => index == length
+                ? LastChildLayoutType.foot
+                : LastChildLayoutType.none,
+            ),
+```
+
+## CloseToTrailing
+
+when reverse property of List is true, layout is as following.
+it likes chat list, and new session will insert to zero index.
+but it's not right when items are not full of viewport.
+
+```
+     trailing
+-----------------
+|               |
+|               |
+|     item2     |
+|     item1     |
+|     item0     |
+-----------------
+     leading
+```
+
+to solve it, you could set closeToTrailing to true, layout is as following.
+support [ExtendedGridView],[ExtendedList],[WaterfallFlow].
+and it also works when reverse is flase, layout will close to trailing.
+
+```
+     trailing
+-----------------
+|     item2     |
+|     item1     |
+|     item0     |
+|               |
+|               |
+-----------------
+     leading
+```
+
+```dart
+      WaterfallFlow.builder(
+        reverse: true,
+        gridDelegate: SliverWaterfallFlowDelegateWithFixedCrossAxisCount(closeToTrailing: true),
+```

analysis_options.yaml

+# Specify analysis options.
+#
+# Until there are meta linter rules, each desired lint must be explicitly enabled.
+# See: https://github.com/dart-lang/linter/issues/288
+#
+# For a list of lints, see: http://dart-lang.github.io/linter/lints/
+# See the configuration guide for more
+# https://github.com/dart-lang/sdk/tree/master/pkg/analyzer#configuring-the-analyzer
+#
+# There are other similar analysis options files in the flutter repos,
+# which should be kept in sync with this file:
+#
+#   - analysis_options.yaml (this file)
+#   - packages/flutter/lib/analysis_options_user.yaml
+#   - https://github.com/flutter/plugins/blob/master/analysis_options.yaml
+#   - https://github.com/flutter/engine/blob/master/analysis_options.yaml
+#
+# This file contains the analysis options used by Flutter tools, such as IntelliJ,
+# Android Studio, and the `flutter analyze` command.
+
+analyzer:
+  strong-mode:
+    implicit-casts: false
+    implicit-dynamic: false
+  errors:
+    # treat missing required parameters as a warning (not a hint)
+    missing_required_param: warning
+    # treat missing returns as a warning (not a hint)
+    missing_return: warning
+    # allow having TODOs in the code
+    todo: ignore
+    # Ignore analyzer hints for updating pubspecs when using Future or
+    # Stream and not importing dart:async
+    # Please see https://github.com/flutter/flutter/pull/24528 for details.
+    sdk_version_async_exported_from_core: ignore
+  # exclude:
+  #   - "bin/cache/**"
+  #   # the following two are relative to the stocks example and the flutter package respectively
+  #   # see https://github.com/dart-lang/sdk/issues/28463
+  #   - "lib/i18n/messages_*.dart"
+  #   - "lib/src/http/**"
+
+linter:
+  rules:
+    # these rules are documented on and in the same order as
+    # the Dart Lint rules page to make maintenance easier
+    # https://github.com/dart-lang/linter/blob/master/example/all.yaml
+    - always_declare_return_types
+    - always_put_control_body_on_new_line
+    # - always_put_required_named_parameters_first # we prefer having parameters in the same order as fields https://github.com/flutter/flutter/issues/10219
+    - always_require_non_null_named_parameters
+    - always_specify_types
+    - annotate_overrides
+    # - avoid_annotating_with_dynamic # conflicts with always_specify_types
+    # - avoid_as # required for implicit-casts: true
+    - avoid_bool_literals_in_conditional_expressions
+    # - avoid_catches_without_on_clauses # we do this commonly
+    # - avoid_catching_errors # we do this commonly
+    - avoid_classes_with_only_static_members
+    # - avoid_double_and_int_checks # only useful when targeting JS runtime
+    - avoid_empty_else
+    # - avoid_equals_and_hash_code_on_mutable_classes # not yet tested
+    - avoid_field_initializers_in_const_classes
+    - avoid_function_literals_in_foreach_calls
+    # - avoid_implementing_value_types # not yet tested
+    - avoid_init_to_null
+    # - avoid_js_rounded_ints # only useful when targeting JS runtime
+    - avoid_null_checks_in_equality_operators
+    # - avoid_positional_boolean_parameters # not yet tested
+    # - avoid_print # not yet tested
+    # - avoid_private_typedef_functions # we prefer having typedef (discussion in https://github.com/flutter/flutter/pull/16356)
+    # - avoid_redundant_argument_values # not yet tested
+    - avoid_relative_lib_imports
+    - avoid_renaming_method_parameters
+    - avoid_return_types_on_setters
+    # - avoid_returning_null # there are plenty of valid reasons to return null
+    # - avoid_returning_null_for_future # not yet tested
+    - avoid_returning_null_for_void
+    # - avoid_returning_this # there are plenty of valid reasons to return this
+    # - avoid_setters_without_getters # not yet tested
+    # - avoid_shadowing_type_parameters # not yet tested
+    - avoid_single_cascade_in_expression_statements
+    - avoid_slow_async_io
+    - avoid_types_as_parameter_names
+    # - avoid_types_on_closure_parameters # conflicts with always_specify_types
+    # - avoid_unnecessary_containers # not yet tested
+    - avoid_unused_constructor_parameters
+    - avoid_void_async
+    # - avoid_web_libraries_in_flutter # not yet tested
+    - await_only_futures
+    - camel_case_extensions
+    - camel_case_types
+    - cancel_subscriptions
+    # - cascade_invocations # not yet tested
+    # - close_sinks # not reliable enough
+    # - comment_references # blocked on https://github.com/flutter/flutter/issues/20765
+    # - constant_identifier_names # needs an opt-out https://github.com/dart-lang/linter/issues/204
+    - control_flow_in_finally
+    # - curly_braces_in_flow_control_structures # not yet tested
+    # - diagnostic_describe_all_properties # not yet tested
+    - directives_ordering
+    - empty_catches
+    - empty_constructor_bodies
+    - empty_statements
+    # - file_names # not yet tested
+    - flutter_style_todos
+    - hash_and_equals
+    - implementation_imports
+    # - invariant_booleans # too many false positives: https://github.com/dart-lang/linter/issues/811
+    - iterable_contains_unrelated_type
+    # - join_return_with_assignment # not yet tested
+    - library_names
+    - library_prefixes
+    # - lines_longer_than_80_chars # not yet tested
+    - list_remove_unrelated_type
+    # - literal_only_boolean_expressions # too many false positives: https://github.com/dart-lang/sdk/issues/34181
+    # - missing_whitespace_between_adjacent_strings # not yet tested
+    - no_adjacent_strings_in_list
+    - no_duplicate_case_values
+    # - no_logic_in_create_state # not yet tested
+    # - no_runtimeType_toString # not yet tested
+    - non_constant_identifier_names
+    # - null_closures  # not yet tested
+    # - omit_local_variable_types # opposite of always_specify_types
+    # - one_member_abstracts # too many false positives
+    # - only_throw_errors # https://github.com/flutter/flutter/issues/5792
+    - overridden_fields
+    - package_api_docs
+    - package_names
+    - package_prefixed_library_names
+    # - parameter_assignments # we do this commonly
+    - prefer_adjacent_string_concatenation
+    - prefer_asserts_in_initializer_lists
+    # - prefer_asserts_with_message # not yet tested
+    - prefer_collection_literals
+    - prefer_conditional_assignment
+    - prefer_const_constructors
+    - prefer_const_constructors_in_immutables
+    - prefer_const_declarations
+    - prefer_const_literals_to_create_immutables
+    # - prefer_constructors_over_static_methods # not yet tested
+    - prefer_contains
+    # - prefer_double_quotes # opposite of prefer_single_quotes
+    - prefer_equal_for_default_values
+    # - prefer_expression_function_bodies # conflicts with https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo#consider-using--for-short-functions-and-methods
+    - prefer_final_fields
+    - prefer_final_in_for_each
+    - prefer_final_locals
+    - prefer_for_elements_to_map_fromIterable
+    - prefer_foreach
+    # - prefer_function_declarations_over_variables # not yet tested
+    - prefer_generic_function_type_aliases
+    - prefer_if_elements_to_conditional_expressions
+    - prefer_if_null_operators
+    - prefer_initializing_formals
+    - prefer_inlined_adds
+    # - prefer_int_literals # not yet tested
+    # - prefer_interpolation_to_compose_strings # not yet tested
+    - prefer_is_empty
+    - prefer_is_not_empty
+    - prefer_is_not_operator
+    - prefer_iterable_whereType
+    # - prefer_mixin # https://github.com/dart-lang/language/issues/32
+    # - prefer_null_aware_operators # disable until NNBD, see https://github.com/flutter/flutter/pull/32711#issuecomment-492930932
+    # - prefer_relative_imports # not yet tested
+    - prefer_single_quotes
+    - prefer_spread_collections
+    - prefer_typing_uninitialized_variables
+    - prefer_void_to_null
+    # - provide_deprecation_message # not yet tested
+    # - public_member_api_docs # enabled on a case-by-case basis; see e.g. packages/analysis_options.yaml
+    - recursive_getters
+    - slash_for_doc_comments
+    # - sort_child_properties_last # not yet tested
+    - sort_constructors_first
+    - sort_pub_dependencies
+    - sort_unnamed_constructors_first
+    - test_types_in_equals
+    - throw_in_finally
+    # - type_annotate_public_apis # subset of always_specify_types
+    - type_init_formals
+    # - unawaited_futures # too many false positives
+    # - unnecessary_await_in_return # not yet tested
+    - unnecessary_brace_in_string_interps
+    - unnecessary_const
+    # - unnecessary_final # conflicts with prefer_final_locals
+    - unnecessary_getters_setters
+    # - unnecessary_lambdas # has false positives: https://github.com/dart-lang/linter/issues/498
+    - unnecessary_new
+    - unnecessary_null_aware_assignments
+    - unnecessary_null_in_if_null_operators
+    - unnecessary_overrides
+    - unnecessary_parenthesis
+    - unnecessary_statements
+    - unnecessary_string_interpolations
+    - unnecessary_this
+    - unrelated_type_equality_checks
+    # - unsafe_html # not yet tested
+    - use_full_hex_values_for_flutter_colors
+    # - use_function_type_syntax_for_parameters # not yet tested
+    # - use_key_in_widget_constructors # not yet tested
+    - use_rethrow_when_possible
+    # - use_setters_to_change_properties # not yet tested
+    # - use_string_buffers # has false positives: https://github.com/dart-lang/sdk/issues/34182
+    # - use_to_and_as_if_applicable # has false positives, so we prefer to catch this by code-review
+    - valid_regexps
+    - void_checks

example/.flutter-plugins-dependencies

+{"info":"This is a generated file; do not edit or check into version control.","plugins":{"ios":[{"name":"path_provider","path":"/Users/qiaomeng/flutter/.pub-cache/hosted/pub.flutter-io.cn/path_provider-1.6.28/","dependencies":[]},{"name":"url_launcher","path":"/Users/qiaomeng/flutter/.pub-cache/hosted/pub.flutter-io.cn/url_launcher-5.3.0/","dependencies":[]}],"android":[{"name":"path_provider","path":"/Users/qiaomeng/flutter/.pub-cache/hosted/pub.flutter-io.cn/path_provider-1.6.28/","dependencies":[]},{"name":"url_launcher","path":"/Users/qiaomeng/flutter/.pub-cache/hosted/pub.flutter-io.cn/url_launcher-5.3.0/","dependencies":[]}],"macos":[{"name":"path_provider_macos","path":"/Users/qiaomeng/flutter/.pub-cache/hosted/pub.flutter-io.cn/path_provider_macos-0.0.4+8/","dependencies":[]}],"linux":[{"name":"path_provider_linux","path":"/Users/qiaomeng/flutter/.pub-cache/hosted/pub.flutter-io.cn/path_provider_linux-0.0.1+2/","dependencies":[]}],"windows":[{"name":"path_provider_windows","path":"/Users/qiaomeng/flutter/.pub-cache/hosted/pub.flutter-io.cn/path_provider_windows-0.0.4+3/","dependencies":[]}],"web":[{"name":"url_launcher_web","path":"/Users/qiaomeng/flutter/.pub-cache/hosted/pub.flutter-io.cn/url_launcher_web-0.1.5+3/","dependencies":[]}]},"dependencyGraph":[{"name":"path_provider","dependencies":["path_provider_macos","path_provider_linux","path_provider_windows"]},{"name":"path_provider_linux","dependencies":[]},{"name":"path_provider_macos","dependencies":[]},{"name":"path_provider_windows","dependencies":[]},{"name":"url_launcher","dependencies":["url_launcher_web"]},{"name":"url_launcher_web","dependencies":[]}],"date_created":"2021-09-28 16:57:14.801573","version":"1.22.4"}
\ No newline at end of file

example/.gitignore

+# Miscellaneous
+*.class
+*.log
+*.pyc
+*.swp
+.DS_Store
+.atom/
+.buildlog/
+.history
+.svn/
+
+# IntelliJ related
+*.iml
+*.ipr
+*.iws
+.idea/
+
+# The .vscode folder contains launch configuration and tasks you configure in
+# VS Code which you may wish to be included in version control, so this line
+# is commented out by default.
+#.vscode/
+
+# Flutter/Dart/Pub related
+**/doc/api/
+.dart_tool/
+.flutter-plugins
+.packages
+.pub-cache/
+.pub/
+/build/
+
+# Web related
+lib/generated_plugin_registrant.dart
+
+# Exceptions to above rules.
+!/packages/flutter_tools/test/data/dart_dependencies_test/**/.packages
+
+
+.packages
+pubspec.lock
\ No newline at end of file

example/.metadata

+# This file tracks properties of this Flutter project.
+# Used by Flutter tool to assess capabilities and perform upgrades etc.
+#
+# This file should be version controlled and should not be manually edited.
+
+version:
+  revision: ee032f67c734e607d8ea5c870ba744daf4bf56e7
+  channel: master
+
+project_type: app

example/README.md

+# example
+
+A new Flutter project.
+
+## Getting Started
+
+This project is a starting point for a Flutter application.
+
+A few resources to get you started if this is your first Flutter project:
+
+- [Lab: Write your first Flutter app](https://flutter.dev/docs/get-started/codelab)
+- [Cookbook: Useful Flutter samples](https://flutter.dev/docs/cookbook)
+
+For help getting started with Flutter, view our
+[online documentation](https://flutter.dev/docs), which offers tutorials,
+samples, guidance on mobile development, and a full API reference.

example/analysis_options.yaml

+# Specify analysis options.
+#
+# Until there are meta linter rules, each desired lint must be explicitly enabled.
+# See: https://github.com/dart-lang/linter/issues/288
+#
+# For a list of lints, see: http://dart-lang.github.io/linter/lints/
+# See the configuration guide for more
+# https://github.com/dart-lang/sdk/tree/master/pkg/analyzer#configuring-the-analyzer
+#
+# There are other similar analysis options files in the flutter repos,
+# which should be kept in sync with this file:
+#
+#   - analysis_options.yaml (this file)
+#   - packages/flutter/lib/analysis_options_user.yaml
+#   - https://github.com/flutter/plugins/blob/master/analysis_options.yaml
+#   - https://github.com/flutter/engine/blob/master/analysis_options.yaml
+#
+# This file contains the analysis options used by Flutter tools, such as IntelliJ,
+# Android Studio, and the `flutter analyze` command.
+
+analyzer:
+  strong-mode:
+    implicit-casts: false
+    implicit-dynamic: false
+  errors:
+    # treat missing required parameters as a warning (not a hint)
+    missing_required_param: warning
+    # treat missing returns as a warning (not a hint)
+    missing_return: warning
+    # allow having TODOs in the code
+    todo: ignore
+    # Ignore analyzer hints for updating pubspecs when using Future or
+    # Stream and not importing dart:async
+    # Please see https://github.com/flutter/flutter/pull/24528 for details.
+    sdk_version_async_exported_from_core: ignore
+  exclude:
+    - "lib/common/data/mock_data.dart"
+  #   # the following two are relative to the stocks example and the flutter package respectively
+  #   # see https://github.com/dart-lang/sdk/issues/28463
+  #   - "lib/i18n/messages_*.dart"
+  #   - "lib/src/http/**"
+
+linter:
+  rules:
+    # these rules are documented on and in the same order as
+    # the Dart Lint rules page to make maintenance easier
+    # https://github.com/dart-lang/linter/blob/master/example/all.yaml
+    - always_declare_return_types
+    - always_put_control_body_on_new_line
+    # - always_put_required_named_parameters_first # we prefer having parameters in the same order as fields https://github.com/flutter/flutter/issues/10219
+    - always_require_non_null_named_parameters
+    - always_specify_types
+    - annotate_overrides
+    # - avoid_annotating_with_dynamic # conflicts with always_specify_types
+    # - avoid_as # required for implicit-casts: true
+    - avoid_bool_literals_in_conditional_expressions
+    # - avoid_catches_without_on_clauses # we do this commonly
+    # - avoid_catching_errors # we do this commonly
+    - avoid_classes_with_only_static_members
+    # - avoid_double_and_int_checks # only useful when targeting JS runtime
+    - avoid_empty_else
+    # - avoid_equals_and_hash_code_on_mutable_classes # not yet tested
+    - avoid_field_initializers_in_const_classes
+    - avoid_function_literals_in_foreach_calls
+    # - avoid_implementing_value_types # not yet tested
+    - avoid_init_to_null
+    # - avoid_js_rounded_ints # only useful when targeting JS runtime
+    - avoid_null_checks_in_equality_operators
+    # - avoid_positional_boolean_parameters # not yet tested
+    # - avoid_print # not yet tested
+    # - avoid_private_typedef_functions # we prefer having typedef (discussion in https://github.com/flutter/flutter/pull/16356)
+    # - avoid_redundant_argument_values # not yet tested
+    - avoid_relative_lib_imports
+    - avoid_renaming_method_parameters
+    - avoid_return_types_on_setters
+    # - avoid_returning_null # there are plenty of valid reasons to return null
+    # - avoid_returning_null_for_future # not yet tested
+    - avoid_returning_null_for_void
+    # - avoid_returning_this # there are plenty of valid reasons to return this
+    # - avoid_setters_without_getters # not yet tested
+    # - avoid_shadowing_type_parameters # not yet tested
+    - avoid_single_cascade_in_expression_statements
+    - avoid_slow_async_io
+    - avoid_types_as_parameter_names
+    # - avoid_types_on_closure_parameters # conflicts with always_specify_types
+    # - avoid_unnecessary_containers # not yet tested
+    - avoid_unused_constructor_parameters
+    - avoid_void_async
+    # - avoid_web_libraries_in_flutter # not yet tested
+    - await_only_futures
+    - camel_case_extensions
+    - camel_case_types
+    - cancel_subscriptions
+    # - cascade_invocations # not yet tested
+    # - close_sinks # not reliable enough
+    # - comment_references # blocked on https://github.com/flutter/flutter/issues/20765
+    # - constant_identifier_names # needs an opt-out https://github.com/dart-lang/linter/issues/204
+    - control_flow_in_finally
+    # - curly_braces_in_flow_control_structures # not yet tested
+    # - diagnostic_describe_all_properties # not yet tested
+    - directives_ordering
+    - empty_catches
+    - empty_constructor_bodies
+    - empty_statements
+    # - file_names # not yet tested
+    - flutter_style_todos
+    - hash_and_equals
+    - implementation_imports
+    # - invariant_booleans # too many false positives: https://github.com/dart-lang/linter/issues/811
+    - iterable_contains_unrelated_type
+    # - join_return_with_assignment # not yet tested
+    - library_names
+    - library_prefixes
+    # - lines_longer_than_80_chars # not yet tested
+    - list_remove_unrelated_type
+    # - literal_only_boolean_expressions # too many false positives: https://github.com/dart-lang/sdk/issues/34181
+    # - missing_whitespace_between_adjacent_strings # not yet tested
+    - no_adjacent_strings_in_list
+    - no_duplicate_case_values
+    # - no_logic_in_create_state # not yet tested
+    # - no_runtimeType_toString # not yet tested
+    - non_constant_identifier_names
+    # - null_closures  # not yet tested
+    # - omit_local_variable_types # opposite of always_specify_types
+    # - one_member_abstracts # too many false positives
+    # - only_throw_errors # https://github.com/flutter/flutter/issues/5792
+    - overridden_fields
+    - package_api_docs
+    - package_names
+    - package_prefixed_library_names
+    # - parameter_assignments # we do this commonly
+    - prefer_adjacent_string_concatenation
+    - prefer_asserts_in_initializer_lists
+    # - prefer_asserts_with_message # not yet tested
+    - prefer_collection_literals
+    - prefer_conditional_assignment
+    - prefer_const_constructors
+    - prefer_const_constructors_in_immutables
+    - prefer_const_declarations
+    - prefer_const_literals_to_create_immutables
+    # - prefer_constructors_over_static_methods # not yet tested
+    - prefer_contains
+    # - prefer_double_quotes # opposite of prefer_single_quotes
+    - prefer_equal_for_default_values
+    # - prefer_expression_function_bodies # conflicts with https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo#consider-using--for-short-functions-and-methods
+    - prefer_final_fields
+    - prefer_final_in_for_each
+    - prefer_final_locals
+    - prefer_for_elements_to_map_fromIterable
+    - prefer_foreach
+    # - prefer_function_declarations_over_variables # not yet tested
+    - prefer_generic_function_type_aliases
+    - prefer_if_elements_to_conditional_expressions
+    - prefer_if_null_operators
+    - prefer_initializing_formals
+    - prefer_inlined_adds
+    # - prefer_int_literals # not yet tested
+    # - prefer_interpolation_to_compose_strings # not yet tested
+    - prefer_is_empty
+    - prefer_is_not_empty
+    - prefer_is_not_operator
+    - prefer_iterable_whereType
+    # - prefer_mixin # https://github.com/dart-lang/language/issues/32
+    # - prefer_null_aware_operators # disable until NNBD, see https://github.com/flutter/flutter/pull/32711#issuecomment-492930932
+    # - prefer_relative_imports # not yet tested
+    - prefer_single_quotes
+    - prefer_spread_collections
+    - prefer_typing_uninitialized_variables
+    - prefer_void_to_null
+    # - provide_deprecation_message # not yet tested
+    # - public_member_api_docs # enabled on a case-by-case basis; see e.g. packages/analysis_options.yaml
+    - recursive_getters
+    - slash_for_doc_comments
+    # - sort_child_properties_last # not yet tested
+    - sort_constructors_first
+    - sort_pub_dependencies
+    - sort_unnamed_constructors_first
+    - test_types_in_equals
+    - throw_in_finally
+    # - type_annotate_public_apis # subset of always_specify_types
+    - type_init_formals
+    # - unawaited_futures # too many false positives
+    # - unnecessary_await_in_return # not yet tested
+    - unnecessary_brace_in_string_interps
+    - unnecessary_const
+    # - unnecessary_final # conflicts with prefer_final_locals
+    - unnecessary_getters_setters
+    # - unnecessary_lambdas # has false positives: https://github.com/dart-lang/linter/issues/498
+    - unnecessary_new
+    - unnecessary_null_aware_assignments
+    - unnecessary_null_in_if_null_operators
+    - unnecessary_overrides
+    - unnecessary_parenthesis
+    - unnecessary_statements
+    - unnecessary_string_interpolations
+    - unnecessary_this
+    - unrelated_type_equality_checks
+    # - unsafe_html # not yet tested
+    - use_full_hex_values_for_flutter_colors
+    # - use_function_type_syntax_for_parameters # not yet tested
+    # - use_key_in_widget_constructors # not yet tested
+    - use_rethrow_when_possible
+    # - use_setters_to_change_properties # not yet tested
+    # - use_string_buffers # has false positives: https://github.com/dart-lang/sdk/issues/34182
+    # - use_to_and_as_if_applicable # has false positives, so we prefer to catch this by code-review
+    - valid_regexps
+    - void_checks

example/android/.gitignore

+gradle-wrapper.jar
+/.gradle
+/captures/
+/gradlew
+/gradlew.bat
+/local.properties
+GeneratedPluginRegistrant.java
+
+# Remember to never publicly share your keystore.
+# See https://flutter.dev/docs/deployment/android#reference-the-keystore-from-the-app
+key.properties

example/android/app/build.gradle

+def localProperties = new Properties()
+def localPropertiesFile = rootProject.file('local.properties')
+if (localPropertiesFile.exists()) {
+    localPropertiesFile.withReader('UTF-8') { reader ->
+        localProperties.load(reader)
+    }
+}
+
+def flutterRoot = localProperties.getProperty('flutter.sdk')
+if (flutterRoot == null) {
+    throw new GradleException("Flutter SDK not found. Define location with flutter.sdk in the local.properties file.")
+}
+
+def flutterVersionCode = localProperties.getProperty('flutter.versionCode')
+if (flutterVersionCode == null) {
+    flutterVersionCode = '1'
+}
+
+def flutterVersionName = localProperties.getProperty('flutter.versionName')
+if (flutterVersionName == null) {
+    flutterVersionName = '1.0'
+}
+
+apply plugin: 'com.android.application'
+apply plugin: 'kotlin-android'
+apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
+
+android {
+    compileSdkVersion 29
+
+    sourceSets {
+        main.java.srcDirs += 'src/main/kotlin'
+    }
+
+    lintOptions {
+        disable 'InvalidPackage'
+    }
+
+    defaultConfig {
+        // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
+        applicationId "com.example.example"
+        minSdkVersion 16
+        targetSdkVersion 29
+        versionCode flutterVersionCode.toInteger()
+        versionName flutterVersionName
+    }
+
+    buildTypes {
+        release {
+            // TODO: Add your own signing config for the release build.
+            // Signing with the debug keys for now, so `flutter run --release` works.
+            signingConfig signingConfigs.debug
+        }
+    }
+}
+
+flutter {
+    source '../..'
+}
+
+dependencies {
+    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
+}

example/android/app/src/debug/AndroidManifest.xml

+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.example.example">
+    <!-- Flutter needs it to communicate with the running application
+         to allow setting breakpoints, to provide hot reload, etc.
+    -->
+    <uses-permission android:name="android.permission.INTERNET"/>
+</manifest>

example/android/app/src/main/AndroidManifest.xml

+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.example.example">
+    <!-- io.flutter.app.FlutterApplication is an android.app.Application that
+         calls FlutterMain.startInitialization(this); in its onCreate method.
+         In most cases you can leave this as-is, but you if you want to provide
+         additional functionality it is fine to subclass or reimplement
+         FlutterApplication and put your custom class here. -->
+    <application
+        android:name="io.flutter.app.FlutterApplication"
+        android:label="example"
+        android:icon="@mipmap/ic_launcher">
+        <activity
+            android:name=".MainActivity"
+            android:launchMode="singleTop"
+            android:theme="@style/LaunchTheme"
+            android:configChanges="orientation|keyboardHidden|keyboard|screenSize|smallestScreenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
+            android:hardwareAccelerated="true"
+            android:windowSoftInputMode="adjustResize">
+            <!-- Specifies an Android theme to apply to this Activity as soon as
+                 the Android process has started. This theme is visible to the user
+                 while the Flutter UI initializes. After that, this theme continues
+                 to determine the Window background behind the Flutter UI. -->
+            <meta-data
+              android:name="io.flutter.embedding.android.NormalTheme"
+              android:resource="@style/NormalTheme"
+              />
+            <!-- Displays an Android View that continues showing the launch screen
+                 Drawable until Flutter paints its first frame, then this splash
+                 screen fades out. A splash screen is useful to avoid any visual
+                 gap between the end of Android's launch screen and the painting of
+                 Flutter's first frame. -->
+            <meta-data
+              android:name="io.flutter.embedding.android.SplashScreenDrawable"
+              android:resource="@drawable/launch_background"
+              />
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN"/>
+                <category android:name="android.intent.category.LAUNCHER"/>
+            </intent-filter>
+        </activity>
+        <!-- Don't delete the meta-data below.
+             This is used by the Flutter tool to generate GeneratedPluginRegistrant.java -->
+        <meta-data
+            android:name="flutterEmbedding"
+            android:value="2" />
+    </application>
+</manifest>

example/android/app/src/main/kotlin/com/example/example/MainActivity.kt

+package com.example.example
+
+import io.flutter.embedding.android.FlutterActivity
+
+class MainActivity: FlutterActivity() {
+}

example/android/app/src/main/res/drawable/launch_background.xml

+<?xml version="1.0" encoding="utf-8"?>
+<!-- Modify this file to customize your launch splash screen -->
+<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
+    <item android:drawable="@android:color/white" />
+
+    <!-- You can insert your own image assets here -->
+    <!-- <item>
+        <bitmap
+            android:gravity="center"
+            android:src="@mipmap/launch_image" />
+    </item> -->
+</layer-list>

example/android/app/src/main/res/values/styles.xml

+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <!-- Theme applied to the Android Window while the process is starting -->
+    <style name="LaunchTheme" parent="@android:style/Theme.Black.NoTitleBar">
+        <!-- Show a splash screen on the activity. Automatically removed when
+             Flutter draws its first frame -->
+        <item name="android:windowBackground">@drawable/launch_background</item>
+    </style>
+    <!-- Theme applied to the Android Window as soon as the process has started.
+         This theme determines the color of the Android Window while your
+         Flutter UI initializes, as well as behind your Flutter UI while its
+         running.
+         
+         This Theme is only used starting with V2 of Flutter's Android embedding. -->
+    <style name="NormalTheme" parent="@android:style/Theme.Black.NoTitleBar">
+        <item name="android:windowBackground">@android:color/white</item>
+    </style>
+</resources>

example/android/app/src/profile/AndroidManifest.xml

+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.example.example">
+    <!-- Flutter needs it to communicate with the running application
+         to allow setting breakpoints, to provide hot reload, etc.
+    -->
+    <uses-permission android:name="android.permission.INTERNET"/>
+</manifest>

example/android/build.gradle

+buildscript {
+    ext.kotlin_version = '1.3.50'
+    repositories {
+        google()
+        jcenter()
+    }
+
+    dependencies {
+        classpath 'com.android.tools.build:gradle:3.5.0'
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
+    }
+}
+
+allprojects {
+    repositories {
+        google()
+        jcenter()
+    }
+}
+
+rootProject.buildDir = '../build'
+subprojects {
+    project.buildDir = "${rootProject.buildDir}/${project.name}"
+}
+subprojects {
+    project.evaluationDependsOn(':app')
+}
+
+task clean(type: Delete) {
+    delete rootProject.buildDir
+}

example/android/gradle.properties

+org.gradle.jvmargs=-Xmx1536M
+android.useAndroidX=true
+android.enableJetifier=true
+android.enableR8=true

example/android/gradle/wrapper/gradle-wrapper.properties

+#Fri Jun 23 08:50:38 CEST 2017
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-5.6.2-all.zip

example/android/settings.gradle

+include ':app'
+
+def localPropertiesFile = new File(rootProject.projectDir, "local.properties")
+def properties = new Properties()
+
+assert localPropertiesFile.exists()
+localPropertiesFile.withReader("UTF-8") { reader -> properties.load(reader) }
+
+def flutterSdkPath = properties.getProperty("flutter.sdk")
+assert flutterSdkPath != null, "flutter.sdk not set in local.properties"
+apply from: "$flutterSdkPath/packages/flutter_tools/gradle/app_plugin_loader.gradle"

example/assets_generator_arguments

+- t f -o lib/common -s
\ No newline at end of file

example/ff_annotation_route_commands

+--route-constants --route-names --route-helper --git flutter_candies_demo_library --no-is-initial-route
\ No newline at end of file

example/ios/.gitignore

+*.mode1v3
+*.mode2v3
+*.moved-aside
+*.pbxuser
+*.perspectivev3
+**/*sync/
+.sconsign.dblite
+.tags*
+**/.vagrant/
+**/DerivedData/
+Icon?
+**/Pods/
+**/.symlinks/
+profile
+xcuserdata
+**/.generated/
+Flutter/App.framework
+Flutter/Flutter.framework
+Flutter/Flutter.podspec
+Flutter/Generated.xcconfig
+Flutter/app.flx
+Flutter/app.zip
+Flutter/flutter_assets/
+Flutter/flutter_export_environment.sh
+ServiceDefinitions.json
+Runner/GeneratedPluginRegistrant.*
+
+# Exceptions to above rules.
+!default.mode1v3
+!default.mode2v3
+!default.pbxuser
+!default.perspectivev3

example/ios/Flutter/AppFrameworkInfo.plist

+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+  <key>CFBundleDevelopmentRegion</key>
+  <string>$(DEVELOPMENT_LANGUAGE)</string>
+  <key>CFBundleExecutable</key>
+  <string>App</string>
+  <key>CFBundleIdentifier</key>
+  <string>io.flutter.flutter.app</string>
+  <key>CFBundleInfoDictionaryVersion</key>
+  <string>6.0</string>
+  <key>CFBundleName</key>
+  <string>App</string>
+  <key>CFBundlePackageType</key>
+  <string>FMWK</string>
+  <key>CFBundleShortVersionString</key>
+  <string>1.0</string>
+  <key>CFBundleSignature</key>
+  <string>????</string>
+  <key>CFBundleVersion</key>
+  <string>1.0</string>
+  <key>MinimumOSVersion</key>
+  <string>9.0</string>
+</dict>
+</plist>

example/ios/Flutter/Debug.xcconfig

+#include "Pods/Target Support Files/Pods-Runner/Pods-Runner.debug.xcconfig"
+#include "Generated.xcconfig"

example/ios/Flutter/Release.xcconfig

+#include "Pods/Target Support Files/Pods-Runner/Pods-Runner.release.xcconfig"
+#include "Generated.xcconfig"

example/ios/Podfile

+# Uncomment this line to define a global platform for your project
+# platform :ios, '9.0'
+
+# CocoaPods analytics sends network stats synchronously affecting flutter build latency.
+ENV['COCOAPODS_DISABLE_STATS'] = 'true'
+
+project 'Runner', {
+  'Debug' => :debug,
+  'Profile' => :release,
+  'Release' => :release,
+}
+
+def flutter_root
+  generated_xcode_build_settings_path = File.expand_path(File.join('..', 'Flutter', 'Generated.xcconfig'), __FILE__)
+  unless File.exist?(generated_xcode_build_settings_path)
+    raise "#{generated_xcode_build_settings_path} must exist. If you're running pod install manually, make sure flutter pub get is executed first"
+  end
+
+  File.foreach(generated_xcode_build_settings_path) do |line|
+    matches = line.match(/FLUTTER_ROOT\=(.*)/)
+    return matches[1].strip if matches
+  end
+  raise "FLUTTER_ROOT not found in #{generated_xcode_build_settings_path}. Try deleting Generated.xcconfig, then run flutter pub get"
+end
+
+require File.expand_path(File.join('packages', 'flutter_tools', 'bin', 'podhelper'), flutter_root)
+
+flutter_ios_podfile_setup
+
+target 'Runner' do
+  use_frameworks!
+  use_modular_headers!
+
+  flutter_install_all_ios_pods File.dirname(File.realpath(__FILE__))
+end
+
+post_install do |installer|
+  installer.pods_project.targets.each do |target|
+    flutter_additional_ios_build_settings(target)
+  end
+end

example/ios/Runner.xcodeproj/project.pbxproj

+// !$*UTF8*$!
+{
+	archiveVersion = 1;
+	classes = {
+	};
+	objectVersion = 46;
+	objects = {
+
+/* Begin PBXBuildFile section */
+		1498D2341E8E89220040F4C2 /* GeneratedPluginRegistrant.m in Sources */ = {isa = PBXBuildFile; fileRef = 1498D2331E8E89220040F4C2 /* GeneratedPluginRegistrant.m */; };
+		3B3967161E833CAA004F5970 /* AppFrameworkInfo.plist in Resources */ = {isa = PBXBuildFile; fileRef = 3B3967151E833CAA004F5970 /* AppFrameworkInfo.plist */; };
+		74858FAF1ED2DC5600515810 /* AppDelegate.swift in Sources */ = {isa = PBXBuildFile; fileRef = 74858FAE1ED2DC5600515810 /* AppDelegate.swift */; };
+		97C146FC1CF9000F007C117D /* Main.storyboard in Resources */ = {isa = PBXBuildFile; fileRef = 97C146FA1CF9000F007C117D /* Main.storyboard */; };
+		97C146FE1CF9000F007C117D /* Assets.xcassets in Resources */ = {isa = PBXBuildFile; fileRef = 97C146FD1CF9000F007C117D /* Assets.xcassets */; };
+		97C147011CF9000F007C117D /* LaunchScreen.storyboard in Resources */ = {isa = PBXBuildFile; fileRef = 97C146FF1CF9000F007C117D /* LaunchScreen.storyboard */; };
+/* End PBXBuildFile section */
+
+/* Begin PBXCopyFilesBuildPhase section */
+		9705A1C41CF9048500538489 /* Embed Frameworks */ = {
+			isa = PBXCopyFilesBuildPhase;
+			buildActionMask = 2147483647;
+			dstPath = "";
+			dstSubfolderSpec = 10;
+			files = (
+			);
+			name = "Embed Frameworks";
+			runOnlyForDeploymentPostprocessing = 0;
+		};
+/* End PBXCopyFilesBuildPhase section */
+
+/* Begin PBXFileReference section */
+		1498D2321E8E86230040F4C2 /* GeneratedPluginRegistrant.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = GeneratedPluginRegistrant.h; sourceTree = "<group>"; };
+		1498D2331E8E89220040F4C2 /* GeneratedPluginRegistrant.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = GeneratedPluginRegistrant.m; sourceTree = "<group>"; };
+		3B3967151E833CAA004F5970 /* AppFrameworkInfo.plist */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.plist.xml; name = AppFrameworkInfo.plist; path = Flutter/AppFrameworkInfo.plist; sourceTree = "<group>"; };
+		74858FAD1ED2DC5600515810 /* Runner-Bridging-Header.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = "Runner-Bridging-Header.h"; sourceTree = "<group>"; };
+		74858FAE1ED2DC5600515810 /* AppDelegate.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = AppDelegate.swift; sourceTree = "<group>"; };
+		7AFA3C8E1D35360C0083082E /* Release.xcconfig */ = {isa = PBXFileReference; lastKnownFileType = text.xcconfig; name = Release.xcconfig; path = Flutter/Release.xcconfig; sourceTree = "<group>"; };
+		9740EEB21CF90195004384FC /* Debug.xcconfig */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.xcconfig; name = Debug.xcconfig; path = Flutter/Debug.xcconfig; sourceTree = "<group>"; };
+		9740EEB31CF90195004384FC /* Generated.xcconfig */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.xcconfig; name = Generated.xcconfig; path = Flutter/Generated.xcconfig; sourceTree = "<group>"; };
+		97C146EE1CF9000F007C117D /* Runner.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = Runner.app; sourceTree = BUILT_PRODUCTS_DIR; };
+		97C146FB1CF9000F007C117D /* Base */ = {isa = PBXFileReference; lastKnownFileType = file.storyboard; name = Base; path = Base.lproj/Main.storyboard; sourceTree = "<group>"; };
+		97C146FD1CF9000F007C117D /* Assets.xcassets */ = {isa = PBXFileReference; lastKnownFileType = folder.assetcatalog; path = Assets.xcassets; sourceTree = "<group>"; };
+		97C147001CF9000F007C117D /* Base */ = {isa = PBXFileReference; lastKnownFileType = file.storyboard; name = Base; path = Base.lproj/LaunchScreen.storyboard; sourceTree = "<group>"; };
+		97C147021CF9000F007C117D /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
+/* End PBXFileReference section */
+
+/* Begin PBXFrameworksBuildPhase section */
+		97C146EB1CF9000F007C117D /* Frameworks */ = {
+			isa = PBXFrameworksBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+		};
+/* End PBXFrameworksBuildPhase section */
+
+/* Begin PBXGroup section */
+		9740EEB11CF90186004384FC /* Flutter */ = {
+			isa = PBXGroup;
+			children = (
+				3B3967151E833CAA004F5970 /* AppFrameworkInfo.plist */,
+				9740EEB21CF90195004384FC /* Debug.xcconfig */,
+				7AFA3C8E1D35360C0083082E /* Release.xcconfig */,
+				9740EEB31CF90195004384FC /* Generated.xcconfig */,
+			);
+			name = Flutter;
+			sourceTree = "<group>";
+		};
+		97C146E51CF9000F007C117D = {
+			isa = PBXGroup;
+			children = (
+				9740EEB11CF90186004384FC /* Flutter */,
+				97C146F01CF9000F007C117D /* Runner */,
+				97C146EF1CF9000F007C117D /* Products */,
+			);
+			sourceTree = "<group>";
+		};
+		97C146EF1CF9000F007C117D /* Products */ = {
+			isa = PBXGroup;
+			children = (
+				97C146EE1CF9000F007C117D /* Runner.app */,
+			);
+			name = Products;
+			sourceTree = "<group>";
+		};
+		97C146F01CF9000F007C117D /* Runner */ = {
+			isa = PBXGroup;
+			children = (
+				97C146FA1CF9000F007C117D /* Main.storyboard */,
+				97C146FD1CF9000F007C117D /* Assets.xcassets */,
+				97C146FF1CF9000F007C117D /* LaunchScreen.storyboard */,
+				97C147021CF9000F007C117D /* Info.plist */,
+				1498D2321E8E86230040F4C2 /* GeneratedPluginRegistrant.h */,
+				1498D2331E8E89220040F4C2 /* GeneratedPluginRegistrant.m */,
+				74858FAE1ED2DC5600515810 /* AppDelegate.swift */,
+				74858FAD1ED2DC5600515810 /* Runner-Bridging-Header.h */,
+			);
+			path = Runner;
+			sourceTree = "<group>";
+		};
+/* End PBXGroup section */
+
+/* Begin PBXNativeTarget section */
+		97C146ED1CF9000F007C117D /* Runner */ = {
+			isa = PBXNativeTarget;
+			buildConfigurationList = 97C147051CF9000F007C117D /* Build configuration list for PBXNativeTarget "Runner" */;
+			buildPhases = (
+				9740EEB61CF901F6004384FC /* Run Script */,
+				97C146EA1CF9000F007C117D /* Sources */,
+				97C146EB1CF9000F007C117D /* Frameworks */,
+				97C146EC1CF9000F007C117D /* Resources */,
+				9705A1C41CF9048500538489 /* Embed Frameworks */,
+				3B06AD1E1E4923F5004D2608 /* Thin Binary */,
+			);
+			buildRules = (
+			);
+			dependencies = (
+			);
+			name = Runner;
+			productName = Runner;
+			productReference = 97C146EE1CF9000F007C117D /* Runner.app */;
+			productType = "com.apple.product-type.application";
+		};
+/* End PBXNativeTarget section */
+
+/* Begin PBXProject section */
+		97C146E61CF9000F007C117D /* Project object */ = {
+			isa = PBXProject;
+			attributes = {
+				LastUpgradeCheck = 1020;
+				ORGANIZATIONNAME = "";
+				TargetAttributes = {
+					97C146ED1CF9000F007C117D = {
+						CreatedOnToolsVersion = 7.3.1;
+						LastSwiftMigration = 1100;
+					};
+				};
+			};
+			buildConfigurationList = 97C146E91CF9000F007C117D /* Build configuration list for PBXProject "Runner" */;
+			compatibilityVersion = "Xcode 9.3";
+			developmentRegion = en;
+			hasScannedForEncodings = 0;
+			knownRegions = (
+				en,
+				Base,
+			);
+			mainGroup = 97C146E51CF9000F007C117D;
+			productRefGroup = 97C146EF1CF9000F007C117D /* Products */;
+			projectDirPath = "";
+			projectRoot = "";
+			targets = (
+				97C146ED1CF9000F007C117D /* Runner */,
+			);
+		};
+/* End PBXProject section */
+
+/* Begin PBXResourcesBuildPhase section */
+		97C146EC1CF9000F007C117D /* Resources */ = {
+			isa = PBXResourcesBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+				97C147011CF9000F007C117D /* LaunchScreen.storyboard in Resources */,
+				3B3967161E833CAA004F5970 /* AppFrameworkInfo.plist in Resources */,
+				97C146FE1CF9000F007C117D /* Assets.xcassets in Resources */,
+				97C146FC1CF9000F007C117D /* Main.storyboard in Resources */,
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+		};
+/* End PBXResourcesBuildPhase section */
+
+/* Begin PBXShellScriptBuildPhase section */
+		3B06AD1E1E4923F5004D2608 /* Thin Binary */ = {
+			isa = PBXShellScriptBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+			);
+			inputPaths = (
+			);
+			name = "Thin Binary";
+			outputPaths = (
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+			shellPath = /bin/sh;
+			shellScript = "/bin/sh \"$FLUTTER_ROOT/packages/flutter_tools/bin/xcode_backend.sh\" embed_and_thin";
+		};
+		9740EEB61CF901F6004384FC /* Run Script */ = {
+			isa = PBXShellScriptBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+			);
+			inputPaths = (
+			);
+			name = "Run Script";
+			outputPaths = (
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+			shellPath = /bin/sh;
+			shellScript = "/bin/sh \"$FLUTTER_ROOT/packages/flutter_tools/bin/xcode_backend.sh\" build";
+		};
+/* End PBXShellScriptBuildPhase section */
+
+/* Begin PBXSourcesBuildPhase section */
+		97C146EA1CF9000F007C117D /* Sources */ = {
+			isa = PBXSourcesBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+				74858FAF1ED2DC5600515810 /* AppDelegate.swift in Sources */,
+				1498D2341E8E89220040F4C2 /* GeneratedPluginRegistrant.m in Sources */,
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+		};
+/* End PBXSourcesBuildPhase section */
+
+/* Begin PBXVariantGroup section */
+		97C146FA1CF9000F007C117D /* Main.storyboard */ = {
+			isa = PBXVariantGroup;
+			children = (
+				97C146FB1CF9000F007C117D /* Base */,
+			);
+			name = Main.storyboard;
+			sourceTree = "<group>";
+		};
+		97C146FF1CF9000F007C117D /* LaunchScreen.storyboard */ = {
+			isa = PBXVariantGroup;
+			children = (
+				97C147001CF9000F007C117D /* Base */,
+			);
+			name = LaunchScreen.storyboard;
+			sourceTree = "<group>";
+		};
+/* End PBXVariantGroup section */
+
+/* Begin XCBuildConfiguration section */
+		249021D3217E4FDB00AE95B9 /* Profile */ = {
+			isa = XCBuildConfiguration;
+			buildSettings = {
+				ALWAYS_SEARCH_USER_PATHS = NO;
+				CLANG_ANALYZER_NONNULL = YES;
+				CLANG_CXX_LANGUAGE_STANDARD = "gnu++0x";
+				CLANG_CXX_LIBRARY = "libc++";
+				CLANG_ENABLE_MODULES = YES;
+				CLANG_ENABLE_OBJC_ARC = YES;
+				CLANG_WARN_BLOCK_CAPTURE_AUTORELEASING = YES;
+				CLANG_WARN_BOOL_CONVERSION = YES;
+				CLANG_WARN_COMMA = YES;
+				CLANG_WARN_CONSTANT_CONVERSION = YES;
+				CLANG_WARN_DEPRECATED_OBJC_IMPLEMENTATIONS = YES;
+				CLANG_WARN_DIRECT_OBJC_ISA_USAGE = YES_ERROR;
+				CLANG_WARN_EMPTY_BODY = YES;
+				CLANG_WARN_ENUM_CONVERSION = YES;
+				CLANG_WARN_INFINITE_RECURSION = YES;
+				CLANG_WARN_INT_CONVERSION = YES;
+				CLANG_WARN_NON_LITERAL_NULL_CONVERSION = YES;
+				CLANG_WARN_OBJC_IMPLICIT_RETAIN_SELF = YES;
+				CLANG_WARN_OBJC_LITERAL_CONVERSION = YES;
+				CLANG_WARN_OBJC_ROOT_CLASS = YES_ERROR;
+				CLANG_WARN_RANGE_LOOP_ANALYSIS = YES;
+				CLANG_WARN_STRICT_PROTOTYPES = YES;
+				CLANG_WARN_SUSPICIOUS_MOVE = YES;
+				CLANG_WARN_UNREACHABLE_CODE = YES;
+				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
+				"CODE_SIGN_IDENTITY[sdk=iphoneos*]" = "iPhone Developer";
+				COPY_PHASE_STRIP = NO;
+				DEBUG_INFORMATION_FORMAT = "dwarf-with-dsym";
+				ENABLE_NS_ASSERTIONS = NO;
+				ENABLE_STRICT_OBJC_MSGSEND = YES;
+				GCC_C_LANGUAGE_STANDARD = gnu99;
+				GCC_NO_COMMON_BLOCKS = YES;
+				GCC_WARN_64_TO_32_BIT_CONVERSION = YES;
+				GCC_WARN_ABOUT_RETURN_TYPE = YES_ERROR;
+				GCC_WARN_UNDECLARED_SELECTOR = YES;
+				GCC_WARN_UNINITIALIZED_AUTOS = YES_AGGRESSIVE;
+				GCC_WARN_UNUSED_FUNCTION = YES;
+				GCC_WARN_UNUSED_VARIABLE = YES;
+				IPHONEOS_DEPLOYMENT_TARGET = 9.0;
+				MTL_ENABLE_DEBUG_INFO = NO;
+				SDKROOT = iphoneos;
+				SUPPORTED_PLATFORMS = iphoneos;
+				TARGETED_DEVICE_FAMILY = "1,2";
+				VALIDATE_PRODUCT = YES;
+			};
+			name = Profile;
+		};
+		249021D4217E4FDB00AE95B9 /* Profile */ = {
+			isa = XCBuildConfiguration;
+			baseConfigurationReference = 7AFA3C8E1D35360C0083082E /* Release.xcconfig */;
+			buildSettings = {
+				ASSETCATALOG_COMPILER_APPICON_NAME = AppIcon;
+				CLANG_ENABLE_MODULES = YES;
+				CURRENT_PROJECT_VERSION = "$(FLUTTER_BUILD_NUMBER)";
+				ENABLE_BITCODE = NO;
+				FRAMEWORK_SEARCH_PATHS = (
+					"$(inherited)",
+					"$(PROJECT_DIR)/Flutter",
+				);
+				INFOPLIST_FILE = Runner/Info.plist;
+				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks";
+				LIBRARY_SEARCH_PATHS = (
+					"$(inherited)",
+					"$(PROJECT_DIR)/Flutter",
+				);
+				PRODUCT_BUNDLE_IDENTIFIER = com.example.example;
+				PRODUCT_NAME = "$(TARGET_NAME)";
+				SWIFT_OBJC_BRIDGING_HEADER = "Runner/Runner-Bridging-Header.h";
+				SWIFT_VERSION = 5.0;
+				VERSIONING_SYSTEM = "apple-generic";
+			};
+			name = Profile;
+		};
+		97C147031CF9000F007C117D /* Debug */ = {
+			isa = XCBuildConfiguration;
+			buildSettings = {
+				ALWAYS_SEARCH_USER_PATHS = NO;
+				CLANG_ANALYZER_NONNULL = YES;
+				CLANG_CXX_LANGUAGE_STANDARD = "gnu++0x";
+				CLANG_CXX_LIBRARY = "libc++";
+				CLANG_ENABLE_MODULES = YES;
+				CLANG_ENABLE_OBJC_ARC = YES;
+				CLANG_WARN_BLOCK_CAPTURE_AUTORELEASING = YES;
+				CLANG_WARN_BOOL_CONVERSION = YES;
+				CLANG_WARN_COMMA = YES;
+				CLANG_WARN_CONSTANT_CONVERSION = YES;
+				CLANG_WARN_DEPRECATED_OBJC_IMPLEMENTATIONS = YES;
+				CLANG_WARN_DIRECT_OBJC_ISA_USAGE = YES_ERROR;
+				CLANG_WARN_EMPTY_BODY = YES;
+				CLANG_WARN_ENUM_CONVERSION = YES;
+				CLANG_WARN_INFINITE_RECURSION = YES;
+				CLANG_WARN_INT_CONVERSION = YES;
+				CLANG_WARN_NON_LITERAL_NULL_CONVERSION = YES;
+				CLANG_WARN_OBJC_IMPLICIT_RETAIN_SELF = YES;
+				CLANG_WARN_OBJC_LITERAL_CONVERSION = YES;
+				CLANG_WARN_OBJC_ROOT_CLASS = YES_ERROR;
+				CLANG_WARN_RANGE_LOOP_ANALYSIS = YES;
+				CLANG_WARN_STRICT_PROTOTYPES = YES;
+				CLANG_WARN_SUSPICIOUS_MOVE = YES;
+				CLANG_WARN_UNREACHABLE_CODE = YES;
+				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
+				"CODE_SIGN_IDENTITY[sdk=iphoneos*]" = "iPhone Developer";
+				COPY_PHASE_STRIP = NO;
+				DEBUG_INFORMATION_FORMAT = dwarf;
+				ENABLE_STRICT_OBJC_MSGSEND = YES;
+				ENABLE_TESTABILITY = YES;
+				GCC_C_LANGUAGE_STANDARD = gnu99;
+				GCC_DYNAMIC_NO_PIC = NO;
+				GCC_NO_COMMON_BLOCKS = YES;
+				GCC_OPTIMIZATION_LEVEL = 0;
+				GCC_PREPROCESSOR_DEFINITIONS = (
+					"DEBUG=1",
+					"$(inherited)",
+				);
+				GCC_WARN_64_TO_32_BIT_CONVERSION = YES;
+				GCC_WARN_ABOUT_RETURN_TYPE = YES_ERROR;
+				GCC_WARN_UNDECLARED_SELECTOR = YES;
+				GCC_WARN_UNINITIALIZED_AUTOS = YES_AGGRESSIVE;
+				GCC_WARN_UNUSED_FUNCTION = YES;
+				GCC_WARN_UNUSED_VARIABLE = YES;
+				IPHONEOS_DEPLOYMENT_TARGET = 9.0;
+				MTL_ENABLE_DEBUG_INFO = YES;
+				ONLY_ACTIVE_ARCH = YES;
+				SDKROOT = iphoneos;
+				TARGETED_DEVICE_FAMILY = "1,2";
+			};
+			name = Debug;
+		};
+		97C147041CF9000F007C117D /* Release */ = {
+			isa = XCBuildConfiguration;
+			buildSettings = {
+				ALWAYS_SEARCH_USER_PATHS = NO;
+				CLANG_ANALYZER_NONNULL = YES;
+				CLANG_CXX_LANGUAGE_STANDARD = "gnu++0x";
+				CLANG_CXX_LIBRARY = "libc++";
+				CLANG_ENABLE_MODULES = YES;
+				CLANG_ENABLE_OBJC_ARC = YES;
+				CLANG_WARN_BLOCK_CAPTURE_AUTORELEASING = YES;
+				CLANG_WARN_BOOL_CONVERSION = YES;
+				CLANG_WARN_COMMA = YES;
+				CLANG_WARN_CONSTANT_CONVERSION = YES;
+				CLANG_WARN_DEPRECATED_OBJC_IMPLEMENTATIONS = YES;
+				CLANG_WARN_DIRECT_OBJC_ISA_USAGE = YES_ERROR;
+				CLANG_WARN_EMPTY_BODY = YES;
+				CLANG_WARN_ENUM_CONVERSION = YES;
+				CLANG_WARN_INFINITE_RECURSION = YES;
+				CLANG_WARN_INT_CONVERSION = YES;
+				CLANG_WARN_NON_LITERAL_NULL_CONVERSION = YES;
+				CLANG_WARN_OBJC_IMPLICIT_RETAIN_SELF = YES;
+				CLANG_WARN_OBJC_LITERAL_CONVERSION = YES;
+				CLANG_WARN_OBJC_ROOT_CLASS = YES_ERROR;
+				CLANG_WARN_RANGE_LOOP_ANALYSIS = YES;
+				CLANG_WARN_STRICT_PROTOTYPES = YES;
+				CLANG_WARN_SUSPICIOUS_MOVE = YES;
+				CLANG_WARN_UNREACHABLE_CODE = YES;
+				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
+				"CODE_SIGN_IDENTITY[sdk=iphoneos*]" = "iPhone Developer";
+				COPY_PHASE_STRIP = NO;
+				DEBUG_INFORMATION_FORMAT = "dwarf-with-dsym";
+				ENABLE_NS_ASSERTIONS = NO;
+				ENABLE_STRICT_OBJC_MSGSEND = YES;
+				GCC_C_LANGUAGE_STANDARD = gnu99;
+				GCC_NO_COMMON_BLOCKS = YES;
+				GCC_WARN_64_TO_32_BIT_CONVERSION = YES;
+				GCC_WARN_ABOUT_RETURN_TYPE = YES_ERROR;
+				GCC_WARN_UNDECLARED_SELECTOR = YES;
+				GCC_WARN_UNINITIALIZED_AUTOS = YES_AGGRESSIVE;
+				GCC_WARN_UNUSED_FUNCTION = YES;
+				GCC_WARN_UNUSED_VARIABLE = YES;
+				IPHONEOS_DEPLOYMENT_TARGET = 9.0;
+				MTL_ENABLE_DEBUG_INFO = NO;
+				SDKROOT = iphoneos;
+				SUPPORTED_PLATFORMS = iphoneos;
+				SWIFT_OPTIMIZATION_LEVEL = "-Owholemodule";
+				TARGETED_DEVICE_FAMILY = "1,2";
+				VALIDATE_PRODUCT = YES;
+			};
+			name = Release;
+		};
+		97C147061CF9000F007C117D /* Debug */ = {
+			isa = XCBuildConfiguration;
+			baseConfigurationReference = 9740EEB21CF90195004384FC /* Debug.xcconfig */;
+			buildSettings = {
+				ASSETCATALOG_COMPILER_APPICON_NAME = AppIcon;
+				CLANG_ENABLE_MODULES = YES;
+				CURRENT_PROJECT_VERSION = "$(FLUTTER_BUILD_NUMBER)";
+				ENABLE_BITCODE = NO;
+				FRAMEWORK_SEARCH_PATHS = (
+					"$(inherited)",
+					"$(PROJECT_DIR)/Flutter",
+				);
+				INFOPLIST_FILE = Runner/Info.plist;
+				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks";
+				LIBRARY_SEARCH_PATHS = (
+					"$(inherited)",
+					"$(PROJECT_DIR)/Flutter",
+				);
+				PRODUCT_BUNDLE_IDENTIFIER = com.example.example;
+				PRODUCT_NAME = "$(TARGET_NAME)";
+				SWIFT_OBJC_BRIDGING_HEADER = "Runner/Runner-Bridging-Header.h";
+				SWIFT_OPTIMIZATION_LEVEL = "-Onone";
+				SWIFT_VERSION = 5.0;
+				VERSIONING_SYSTEM = "apple-generic";
+			};
+			name = Debug;
+		};
+		97C147071CF9000F007C117D /* Release */ = {
+			isa = XCBuildConfiguration;
+			baseConfigurationReference = 7AFA3C8E1D35360C0083082E /* Release.xcconfig */;
+			buildSettings = {
+				ASSETCATALOG_COMPILER_APPICON_NAME = AppIcon;
+				CLANG_ENABLE_MODULES = YES;
+				CURRENT_PROJECT_VERSION = "$(FLUTTER_BUILD_NUMBER)";
+				ENABLE_BITCODE = NO;
+				FRAMEWORK_SEARCH_PATHS = (
+					"$(inherited)",
+					"$(PROJECT_DIR)/Flutter",
+				);
+				INFOPLIST_FILE = Runner/Info.plist;
+				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks";
+				LIBRARY_SEARCH_PATHS = (
+					"$(inherited)",
+					"$(PROJECT_DIR)/Flutter",
+				);
+				PRODUCT_BUNDLE_IDENTIFIER = com.example.example;
+				PRODUCT_NAME = "$(TARGET_NAME)";
+				SWIFT_OBJC_BRIDGING_HEADER = "Runner/Runner-Bridging-Header.h";
+				SWIFT_VERSION = 5.0;
+				VERSIONING_SYSTEM = "apple-generic";
+			};
+			name = Release;
+		};
+/* End XCBuildConfiguration section */
+
+/* Begin XCConfigurationList section */
+		97C146E91CF9000F007C117D /* Build configuration list for PBXProject "Runner" */ = {
+			isa = XCConfigurationList;
+			buildConfigurations = (
+				97C147031CF9000F007C117D /* Debug */,
+				97C147041CF9000F007C117D /* Release */,
+				249021D3217E4FDB00AE95B9 /* Profile */,
+			);
+			defaultConfigurationIsVisible = 0;
+			defaultConfigurationName = Release;
+		};
+		97C147051CF9000F007C117D /* Build configuration list for PBXNativeTarget "Runner" */ = {
+			isa = XCConfigurationList;
+			buildConfigurations = (
+				97C147061CF9000F007C117D /* Debug */,
+				97C147071CF9000F007C117D /* Release */,
+				249021D4217E4FDB00AE95B9 /* Profile */,
+			);
+			defaultConfigurationIsVisible = 0;
+			defaultConfigurationName = Release;
+		};
+/* End XCConfigurationList section */
+	};
+	rootObject = 97C146E61CF9000F007C117D /* Project object */;
+}

example/ios/Runner.xcodeproj/project.xcworkspace/contents.xcworkspacedata

+<?xml version="1.0" encoding="UTF-8"?>
+<Workspace
+   version = "1.0">
+   <FileRef
+      location = "group:Runner.xcodeproj">
+   </FileRef>
+</Workspace>

example/ios/Runner.xcodeproj/project.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist

+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>IDEDidComputeMac32BitWarning</key>
+	<true/>
+</dict>
+</plist>

example/ios/Runner.xcodeproj/project.xcworkspace/xcshareddata/WorkspaceSettings.xcsettings

+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>PreviewsEnabled</key>
+	<false/>
+</dict>
+</plist>

example/ios/Runner.xcodeproj/xcshareddata/xcschemes/Runner.xcscheme

+<?xml version="1.0" encoding="UTF-8"?>
+<Scheme
+   LastUpgradeVersion = "1020"
+   version = "1.3">
+   <BuildAction
+      parallelizeBuildables = "YES"
+      buildImplicitDependencies = "YES">
+      <BuildActionEntries>
+         <BuildActionEntry
+            buildForTesting = "YES"
+            buildForRunning = "YES"
+            buildForProfiling = "YES"
+            buildForArchiving = "YES"
+            buildForAnalyzing = "YES">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "97C146ED1CF9000F007C117D"
+               BuildableName = "Runner.app"
+               BlueprintName = "Runner"
+               ReferencedContainer = "container:Runner.xcodeproj">
+            </BuildableReference>
+         </BuildActionEntry>
+      </BuildActionEntries>
+   </BuildAction>
+   <TestAction
+      buildConfiguration = "Debug"
+      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
+      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      shouldUseLaunchSchemeArgsEnv = "YES">
+      <Testables>
+      </Testables>
+      <MacroExpansion>
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "97C146ED1CF9000F007C117D"
+            BuildableName = "Runner.app"
+            BlueprintName = "Runner"
+            ReferencedContainer = "container:Runner.xcodeproj">
+         </BuildableReference>
+      </MacroExpansion>
+      <AdditionalOptions>
+      </AdditionalOptions>
+   </TestAction>
+   <LaunchAction
+      buildConfiguration = "Debug"
+      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
+      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      launchStyle = "0"
+      useCustomWorkingDirectory = "NO"
+      ignoresPersistentStateOnLaunch = "NO"
+      debugDocumentVersioning = "YES"
+      debugServiceExtension = "internal"
+      allowLocationSimulation = "YES">
+      <BuildableProductRunnable
+         runnableDebuggingMode = "0">
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "97C146ED1CF9000F007C117D"
+            BuildableName = "Runner.app"
+            BlueprintName = "Runner"
+            ReferencedContainer = "container:Runner.xcodeproj">
+         </BuildableReference>
+      </BuildableProductRunnable>
+      <AdditionalOptions>
+      </AdditionalOptions>
+   </LaunchAction>
+   <ProfileAction
+      buildConfiguration = "Profile"
+      shouldUseLaunchSchemeArgsEnv = "YES"
+      savedToolIdentifier = ""
+      useCustomWorkingDirectory = "NO"
+      debugDocumentVersioning = "YES">
+      <BuildableProductRunnable
+         runnableDebuggingMode = "0">
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "97C146ED1CF9000F007C117D"
+            BuildableName = "Runner.app"
+            BlueprintName = "Runner"
+            ReferencedContainer = "container:Runner.xcodeproj">
+         </BuildableReference>
+      </BuildableProductRunnable>
+   </ProfileAction>
+   <AnalyzeAction
+      buildConfiguration = "Debug">
+   </AnalyzeAction>
+   <ArchiveAction
+      buildConfiguration = "Release"
+      revealArchiveInOrganizer = "YES">
+   </ArchiveAction>
+</Scheme>

example/ios/Runner.xcworkspace/contents.xcworkspacedata

+<?xml version="1.0" encoding="UTF-8"?>
+<Workspace
+   version = "1.0">
+   <FileRef
+      location = "group:Runner.xcodeproj">
+   </FileRef>
+</Workspace>

example/ios/Runner.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist

+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>IDEDidComputeMac32BitWarning</key>
+	<true/>
+</dict>
+</plist>

example/ios/Runner.xcworkspace/xcshareddata/WorkspaceSettings.xcsettings

+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>PreviewsEnabled</key>
+	<false/>
+</dict>
+</plist>

example/ios/Runner/AppDelegate.swift

+import UIKit
+import Flutter
+
+@UIApplicationMain
+@objc class AppDelegate: FlutterAppDelegate {
+  override func application(
+    _ application: UIApplication,
+    didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
+  ) -> Bool {
+    GeneratedPluginRegistrant.register(with: self)
+    return super.application(application, didFinishLaunchingWithOptions: launchOptions)
+  }
+}

example/ios/Runner/Assets.xcassets/AppIcon.appiconset/Contents.json

+{
+  "images" : [
+    {
+      "size" : "20x20",
+      "idiom" : "iphone",
+      "filename" : "Icon-App-20x20@2x.png",
+      "scale" : "2x"
+    },
+    {
+      "size" : "20x20",
+      "idiom" : "iphone",
+      "filename" : "Icon-App-20x20@3x.png",
+      "scale" : "3x"
+    },
+    {
+      "size" : "29x29",
+      "idiom" : "iphone",
+      "filename" : "Icon-App-29x29@1x.png",
+      "scale" : "1x"
+    },
+    {
+      "size" : "29x29",
+      "idiom" : "iphone",
+      "filename" : "Icon-App-29x29@2x.png",
+      "scale" : "2x"
+    },
+    {
+      "size" : "29x29",
+      "idiom" : "iphone",
+      "filename" : "Icon-App-29x29@3x.png",
+      "scale" : "3x"
+    },
+    {
+      "size" : "40x40",
+      "idiom" : "iphone",
+      "filename" : "Icon-App-40x40@2x.png",
+      "scale" : "2x"
+    },
+    {
+      "size" : "40x40",
+      "idiom" : "iphone",
+      "filename" : "Icon-App-40x40@3x.png",
+      "scale" : "3x"
+    },
+    {
+      "size" : "60x60",
+      "idiom" : "iphone",
+      "filename" : "Icon-App-60x60@2x.png",
+      "scale" : "2x"
+    },
+    {
+      "size" : "60x60",
+      "idiom" : "iphone",
+      "filename" : "Icon-App-60x60@3x.png",
+      "scale" : "3x"
+    },
+    {
+      "size" : "20x20",
+      "idiom" : "ipad",
+      "filename" : "Icon-App-20x20@1x.png",
+      "scale" : "1x"
+    },
+    {
+      "size" : "20x20",
+      "idiom" : "ipad",
+      "filename" : "Icon-App-20x20@2x.png",
+      "scale" : "2x"
+    },
+    {
+      "size" : "29x29",
+      "idiom" : "ipad",
+      "filename" : "Icon-App-29x29@1x.png",
+      "scale" : "1x"
+    },
+    {
+      "size" : "29x29",
+      "idiom" : "ipad",
+      "filename" : "Icon-App-29x29@2x.png",
+      "scale" : "2x"
+    },
+    {
+      "size" : "40x40",
+      "idiom" : "ipad",
+      "filename" : "Icon-App-40x40@1x.png",
+      "scale" : "1x"
+    },
+    {
+      "size" : "40x40",
+      "idiom" : "ipad",
+      "filename" : "Icon-App-40x40@2x.png",
+      "scale" : "2x"
+    },
+    {
+      "size" : "76x76",
+      "idiom" : "ipad",
+      "filename" : "Icon-App-76x76@1x.png",
+      "scale" : "1x"
+    },
+    {
+      "size" : "76x76",
+      "idiom" : "ipad",
+      "filename" : "Icon-App-76x76@2x.png",
+      "scale" : "2x"
+    },
+    {
+      "size" : "83.5x83.5",
+      "idiom" : "ipad",
+      "filename" : "Icon-App-83.5x83.5@2x.png",
+      "scale" : "2x"
+    },
+    {
+      "size" : "1024x1024",
+      "idiom" : "ios-marketing",
+      "filename" : "Icon-App-1024x1024@1x.png",
+      "scale" : "1x"
+    }
+  ],
+  "info" : {
+    "version" : 1,
+    "author" : "xcode"
+  }
+}

example/ios/Runner/Assets.xcassets/LaunchImage.imageset/Contents.json

+{
+  "images" : [
+    {
+      "idiom" : "universal",
+      "filename" : "LaunchImage.png",
+      "scale" : "1x"
+    },
+    {
+      "idiom" : "universal",
+      "filename" : "LaunchImage@2x.png",
+      "scale" : "2x"
+    },
+    {
+      "idiom" : "universal",
+      "filename" : "LaunchImage@3x.png",
+      "scale" : "3x"
+    }
+  ],
+  "info" : {
+    "version" : 1,
+    "author" : "xcode"
+  }
+}

example/ios/Runner/Assets.xcassets/LaunchImage.imageset/README.md

+# Launch Screen Assets
+
+You can customize the launch screen with your own desired assets by replacing the image files in this directory.
+
+You can also do it by opening your Flutter project's Xcode project with `open ios/Runner.xcworkspace`, selecting `Runner/Assets.xcassets` in the Project Navigator and dropping in the desired images.
\ No newline at end of file

example/ios/Runner/Base.lproj/LaunchScreen.storyboard

+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<document type="com.apple.InterfaceBuilder3.CocoaTouch.Storyboard.XIB" version="3.0" toolsVersion="12121" systemVersion="16G29" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" launchScreen="YES" colorMatched="YES" initialViewController="01J-lp-oVM">
+    <dependencies>
+        <deployment identifier="iOS"/>
+        <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="12089"/>
+    </dependencies>
+    <scenes>
+        <!--View Controller-->
+        <scene sceneID="EHf-IW-A2E">
+            <objects>
+                <viewController id="01J-lp-oVM" sceneMemberID="viewController">
+                    <layoutGuides>
+                        <viewControllerLayoutGuide type="top" id="Ydg-fD-yQy"/>
+                        <viewControllerLayoutGuide type="bottom" id="xbc-2k-c8Z"/>
+                    </layoutGuides>
+                    <view key="view" contentMode="scaleToFill" id="Ze5-6b-2t3">
+                        <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
+                        <subviews>
+                            <imageView opaque="NO" clipsSubviews="YES" multipleTouchEnabled="YES" contentMode="center" image="LaunchImage" translatesAutoresizingMaskIntoConstraints="NO" id="YRO-k0-Ey4">
+                            </imageView>
+                        </subviews>
+                        <color key="backgroundColor" red="1" green="1" blue="1" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
+                        <constraints>
+                            <constraint firstItem="YRO-k0-Ey4" firstAttribute="centerX" secondItem="Ze5-6b-2t3" secondAttribute="centerX" id="1a2-6s-vTC"/>
+                            <constraint firstItem="YRO-k0-Ey4" firstAttribute="centerY" secondItem="Ze5-6b-2t3" secondAttribute="centerY" id="4X2-HB-R7a"/>
+                        </constraints>
+                    </view>
+                </viewController>
+                <placeholder placeholderIdentifier="IBFirstResponder" id="iYj-Kq-Ea1" userLabel="First Responder" sceneMemberID="firstResponder"/>
+            </objects>
+            <point key="canvasLocation" x="53" y="375"/>
+        </scene>
+    </scenes>
+    <resources>
+        <image name="LaunchImage" width="168" height="185"/>
+    </resources>
+</document>

example/ios/Runner/Base.lproj/Main.storyboard

+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<document type="com.apple.InterfaceBuilder3.CocoaTouch.Storyboard.XIB" version="3.0" toolsVersion="10117" systemVersion="15F34" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES" initialViewController="BYZ-38-t0r">
+    <dependencies>
+        <deployment identifier="iOS"/>
+        <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="10085"/>
+    </dependencies>
+    <scenes>
+        <!--Flutter View Controller-->
+        <scene sceneID="tne-QT-ifu">
+            <objects>
+                <viewController id="BYZ-38-t0r" customClass="FlutterViewController" sceneMemberID="viewController">
+                    <layoutGuides>
+                        <viewControllerLayoutGuide type="top" id="y3c-jy-aDJ"/>
+                        <viewControllerLayoutGuide type="bottom" id="wfy-db-euE"/>
+                    </layoutGuides>
+                    <view key="view" contentMode="scaleToFill" id="8bC-Xf-vdC">
+                        <rect key="frame" x="0.0" y="0.0" width="600" height="600"/>
+                        <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
+                        <color key="backgroundColor" white="1" alpha="1" colorSpace="custom" customColorSpace="calibratedWhite"/>
+                    </view>
+                </viewController>
+                <placeholder placeholderIdentifier="IBFirstResponder" id="dkx-z0-nzr" sceneMemberID="firstResponder"/>
+            </objects>
+        </scene>
+    </scenes>
+</document>

example/ios/Runner/Info.plist

+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>CFBundleDevelopmentRegion</key>
+	<string>$(DEVELOPMENT_LANGUAGE)</string>
+	<key>CFBundleExecutable</key>
+	<string>$(EXECUTABLE_NAME)</string>
+	<key>CFBundleIdentifier</key>
+	<string>$(PRODUCT_BUNDLE_IDENTIFIER)</string>
+	<key>CFBundleInfoDictionaryVersion</key>
+	<string>6.0</string>
+	<key>CFBundleName</key>
+	<string>example</string>
+	<key>CFBundlePackageType</key>
+	<string>APPL</string>
+	<key>CFBundleShortVersionString</key>
+	<string>$(FLUTTER_BUILD_NAME)</string>
+	<key>CFBundleSignature</key>
+	<string>????</string>
+	<key>CFBundleVersion</key>
+	<string>$(FLUTTER_BUILD_NUMBER)</string>
+	<key>LSRequiresIPhoneOS</key>
+	<true/>
+	<key>UILaunchStoryboardName</key>
+	<string>LaunchScreen</string>
+	<key>UIMainStoryboardFile</key>
+	<string>Main</string>
+	<key>UISupportedInterfaceOrientations</key>
+	<array>
+		<string>UIInterfaceOrientationPortrait</string>
+		<string>UIInterfaceOrientationLandscapeLeft</string>
+		<string>UIInterfaceOrientationLandscapeRight</string>
+	</array>
+	<key>UISupportedInterfaceOrientations~ipad</key>
+	<array>
+		<string>UIInterfaceOrientationPortrait</string>
+		<string>UIInterfaceOrientationPortraitUpsideDown</string>
+		<string>UIInterfaceOrientationLandscapeLeft</string>
+		<string>UIInterfaceOrientationLandscapeRight</string>
+	</array>
+	<key>UIViewControllerBasedStatusBarAppearance</key>
+	<false/>
+</dict>
+</plist>

example/ios/Runner/Runner-Bridging-Header.h

+#import "GeneratedPluginRegistrant.h"

example/lib/example_route.dart

+// GENERATED CODE - DO NOT MODIFY MANUALLY
+// **************************************************************************
+// Auto generated by https://github.com/fluttercandies/ff_annotation_route
+// **************************************************************************
+
+import 'package:ff_annotation_route/ff_annotation_route.dart';
+import 'package:flutter/widgets.dart';
+import 'pages/main_page.dart';
+import 'pages/simple/custom_scrollView_demo.dart';
+import 'pages/simple/random_sized_demo.dart';
+
+RouteResult getRouteResult({String name, Map<String, dynamic> arguments}) {
+  arguments = arguments ?? const <String, dynamic>{};
+  switch (name) {
+    case 'fluttercandies://custom_scrollview':
+      return RouteResult(
+        name: name,
+        widget: CustomScrollviewDemo(),
+        routeName: 'custom_scrollview',
+        description: 'show how to build waterfall flow in CustomScrollview.',
+        exts: <String, dynamic>{'group': 'Simple', 'order': 1},
+      );
+    case 'fluttercandies://demogrouppage':
+      return RouteResult(
+        name: name,
+        widget: DemoGroupPage(
+          keyValue:
+              arguments['keyValue'] as MapEntry<String, List<DemoRouteResult>>,
+        ),
+        routeName: 'DemoGroupPage',
+      );
+    case 'fluttercandies://known-sized':
+      return RouteResult(
+        name: name,
+        routeName: 'known-sized',
+        description:
+            'show how to build a known-sized item with waterfall flow list.',
+        exts: <String, dynamic>{'group': 'Complex', 'order': 1},
+      );
+    case 'fluttercandies://mainpage':
+      return RouteResult(
+        name: name,
+        widget: MainPage(),
+        routeName: 'MainPage',
+      );
+    case 'fluttercandies://random-sized':
+      return RouteResult(
+        name: name,
+        widget: RandomSizedDemo(),
+        routeName: 'random-sized',
+        description:
+            'show how to build random-sized item with waterfall flow list.',
+        exts: <String, dynamic>{'group': 'Simple', 'order': 0},
+      );
+    case 'fluttercandies://variable-sized':
+      return RouteResult(
+        name: name,
+        routeName: 'variable-sized',
+        description:
+            'show how to build a variable-sized item with waterfall flow list.',
+        exts: <String, dynamic>{'group': 'Complex', 'order': 1},
+      );
+    default:
+      return const RouteResult(name: 'flutterCandies://notfound');
+  }
+}
+
+class RouteResult {
+  const RouteResult({
+    @required this.name,
+    this.widget,
+    this.showStatusBar = true,
+    this.routeName = '',
+    this.pageRouteType,
+    this.description = '',
+    this.exts,
+  });
+
+  /// The name of the route (e.g., "/settings").
+  ///
+  /// If null, the route is anonymous.
+  final String name;
+
+  /// The Widget return base on route
+  final Widget widget;
+
+  /// Whether show this route with status bar.
+  final bool showStatusBar;
+
+  /// The route name to track page
+  final String routeName;
+
+  /// The type of page route
+  final PageRouteType pageRouteType;
+
+  /// The description of route
+  final String description;
+
+  /// The extend arguments
+  final Map<String, dynamic> exts;
+}

example/lib/example_route_helper.dart

+// GENERATED CODE - DO NOT MODIFY MANUALLY
+// **************************************************************************
+// Auto generated by https://github.com/fluttercandies/ff_annotation_route
+// **************************************************************************
+
+import 'dart:io';
+
+import 'package:flutter/material.dart';
+import 'package:flutter/cupertino.dart';
+import 'package:flutter/foundation.dart';
+import 'package:flutter/widgets.dart';
+import 'package:ff_annotation_route/ff_annotation_route.dart';
+
+import 'example_route.dart';
+
+class FFNavigatorObserver extends NavigatorObserver {
+  FFNavigatorObserver({this.routeChange});
+
+  final RouteChange routeChange;
+
+  @override
+  void didPop(Route<dynamic> route, Route<dynamic> previousRoute) {
+    super.didPop(route, previousRoute);
+    _didRouteChange(previousRoute, route);
+  }
+
+  @override
+  void didPush(Route<dynamic> route, Route<dynamic> previousRoute) {
+    super.didPush(route, previousRoute);
+    _didRouteChange(route, previousRoute);
+  }
+
+  @override
+  void didRemove(Route<dynamic> route, Route<dynamic> previousRoute) {
+    super.didRemove(route, previousRoute);
+    _didRouteChange(previousRoute, route);
+  }
+
+  @override
+  void didReplace({Route<dynamic> newRoute, Route<dynamic> oldRoute}) {
+    super.didReplace(newRoute: newRoute, oldRoute: oldRoute);
+    _didRouteChange(newRoute, oldRoute);
+  }
+
+  void _didRouteChange(Route<dynamic> newRoute, Route<dynamic> oldRoute) {
+    // oldRoute may be null when route first time enter.
+    routeChange?.call(newRoute, oldRoute);
+  }
+}
+
+typedef RouteChange = void Function(
+    Route<dynamic> newRoute, Route<dynamic> oldRoute);
+
+class FFTransparentPageRoute<T> extends PageRouteBuilder<T> {
+  FFTransparentPageRoute({
+    RouteSettings settings,
+    @required RoutePageBuilder pageBuilder,
+    RouteTransitionsBuilder transitionsBuilder = _defaultTransitionsBuilder,
+    Duration transitionDuration = const Duration(milliseconds: 150),
+    bool barrierDismissible = false,
+    Color barrierColor,
+    String barrierLabel,
+    bool maintainState = true,
+  })  : assert(pageBuilder != null),
+        assert(transitionsBuilder != null),
+        assert(barrierDismissible != null),
+        assert(maintainState != null),
+        super(
+          settings: settings,
+          opaque: false,
+          pageBuilder: pageBuilder,
+          transitionsBuilder: transitionsBuilder,
+          transitionDuration: transitionDuration,
+          barrierDismissible: barrierDismissible,
+          barrierColor: barrierColor,
+          barrierLabel: barrierLabel,
+          maintainState: maintainState,
+        );
+}
+
+Widget _defaultTransitionsBuilder(
+  BuildContext context,
+  Animation<double> animation,
+  Animation<double> secondaryAnimation,
+  Widget child,
+) {
+  return FadeTransition(
+    opacity: CurvedAnimation(
+      parent: animation,
+      curve: Curves.easeOut,
+    ),
+    child: child,
+  );
+}
+
+Route<dynamic> onGenerateRouteHelper(
+  RouteSettings settings, {
+  Widget notFoundFallback,
+  Object arguments,
+  WidgetBuilder builder,
+}) {
+  arguments ??= settings.arguments;
+
+  final RouteResult routeResult = getRouteResult(
+    name: settings.name,
+    arguments: arguments as Map<String, dynamic>,
+  );
+  if (routeResult.showStatusBar != null || routeResult.routeName != null) {
+    settings = FFRouteSettings(
+      name: settings.name,
+      routeName: routeResult.routeName,
+      arguments: arguments as Map<String, dynamic>,
+      showStatusBar: routeResult.showStatusBar,
+    );
+  }
+  Widget page = routeResult.widget ?? notFoundFallback;
+  if (page == null) {
+    throw Exception(
+      '''Route "${settings.name}" returned null. Route Widget must never return null,
+          maybe the reason is that route name did not match with right path.
+          You can use parameter[notFoundFallback] to avoid this ugly error.''',
+    );
+  }
+
+  if (arguments is Map<String, dynamic>) {
+    final RouteBuilder builder = arguments['routeBuilder'] as RouteBuilder;
+    if (builder != null) {
+      return builder(page);
+    }
+  }
+
+  if (builder != null) {
+    page = builder(page, routeResult);
+  }
+
+  switch (routeResult.pageRouteType) {
+    case PageRouteType.material:
+      return MaterialPageRoute<dynamic>(
+        settings: settings,
+        builder: (BuildContext _) => page,
+      );
+    case PageRouteType.cupertino:
+      return CupertinoPageRoute<dynamic>(
+        settings: settings,
+        builder: (BuildContext _) => page,
+      );
+    case PageRouteType.transparent:
+      return FFTransparentPageRoute<dynamic>(
+        settings: settings,
+        pageBuilder: (
+          BuildContext _,
+          Animation<double> __,
+          Animation<double> ___,
+        ) =>
+            page,
+      );
+    default:
+      return kIsWeb || !Platform.isIOS
+          ? MaterialPageRoute<dynamic>(
+              settings: settings,
+              builder: (BuildContext _) => page,
+            )
+          : CupertinoPageRoute<dynamic>(
+              settings: settings,
+              builder: (BuildContext _) => page,
+            );
+  }
+}
+
+typedef RouteBuilder = PageRoute<dynamic> Function(Widget page);
+
+class FFRouteSettings extends RouteSettings {
+  const FFRouteSettings({
+    this.routeName,
+    this.showStatusBar,
+    String name,
+    Object arguments,
+  }) : super(
+          name: name,
+          arguments: arguments,
+        );
+
+  final String routeName;
+  final bool showStatusBar;
+}
+
+/// Signature for a function that creates a widget, e.g.
+typedef WidgetBuilder = Widget Function(Widget child, RouteResult routeResult);

example/lib/example_routes.dart

+// GENERATED CODE - DO NOT MODIFY MANUALLY
+// **************************************************************************
+// Auto generated by https://github.com/fluttercandies/ff_annotation_route
+// **************************************************************************
+const List<String> routeNames = <String>[
+  'fluttercandies://custom_scrollview',
+  'fluttercandies://demogrouppage',
+  'fluttercandies://known-sized',
+  'fluttercandies://mainpage',
+  'fluttercandies://random-sized',
+  'fluttercandies://variable-sized',
+];
+
+class Routes {
+  const Routes._();
+
+  /// 'show how to build waterfall flow in CustomScrollview.'
+  ///
+  /// [name] : 'fluttercandies://custom_scrollview'
+  ///
+  /// [routeName] : 'custom_scrollview'
+  ///
+  /// [description] : 'show how to build waterfall flow in CustomScrollview.'
+  ///
+  /// [exts] : {group: Simple, order: 1}
+  static const String fluttercandiesCustomScrollview =
+      'fluttercandies://custom_scrollview';
+
+  /// 'DemoGroupPage'
+  ///
+  /// [name] : 'fluttercandies://demogrouppage'
+  ///
+  /// [routeName] : 'DemoGroupPage'
+  ///
+  /// [constructors] :
+  ///
+  /// DemoGroupPage : [MapEntry<String, List<DemoRouteResult>> keyValue]
+  static const String fluttercandiesDemogrouppage =
+      'fluttercandies://demogrouppage';
+
+  /// 'show how to build a known-sized item with waterfall flow list.'
+  ///
+  /// [name] : 'fluttercandies://known-sized'
+  ///
+  /// [routeName] : 'known-sized'
+  ///
+  /// [description] : 'show how to build a known-sized item with waterfall flow list.'
+  ///
+  /// [exts] : {group: Complex, order: 1}
+  static const String fluttercandiesKnownSized = 'fluttercandies://known-sized';
+
+  /// 'MainPage'
+  ///
+  /// [name] : 'fluttercandies://mainpage'
+  ///
+  /// [routeName] : 'MainPage'
+  ///
+  /// [constructors] :
+  ///
+  /// MainPage : []
+  static const String fluttercandiesMainpage = 'fluttercandies://mainpage';
+
+  /// 'show how to build random-sized item with waterfall flow list.'
+  ///
+  /// [name] : 'fluttercandies://random-sized'
+  ///
+  /// [routeName] : 'random-sized'
+  ///
+  /// [description] : 'show how to build random-sized item with waterfall flow list.'
+  ///
+  /// [exts] : {group: Simple, order: 0}
+  static const String fluttercandiesRandomSized =
+      'fluttercandies://random-sized';
+
+  /// 'show how to build a variable-sized item with waterfall flow list.'
+  ///
+  /// [name] : 'fluttercandies://variable-sized'
+  ///
+  /// [routeName] : 'variable-sized'
+  ///
+  /// [description] : 'show how to build a variable-sized item with waterfall flow list.'
+  ///
+  /// [exts] : {group: Complex, order: 1}
+  static const String fluttercandiesVariableSized =
+      'fluttercandies://variable-sized';
+}

example/lib/main.dart

+import 'package:flutter/cupertino.dart';
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_sliver_tracker/flutter_sliver_tracker.dart';
+import 'package:waterfall_flow/waterfall_flow.dart';
+
+void main() => runApp(MyApp());
+
+class MyApp extends StatelessWidget {
+  // This widget is the root of your application.
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      title: '封装曝光',
+      debugShowCheckedModeBanner: false,
+      theme: ThemeData(primarySwatch: Colors.blue),
+      home: const HomePage(),
+    );
+  }
+}
+
+
+class HomePage extends StatefulWidget {
+  const HomePage({ Key key }) : super(key: key);
+
+  @override
+  _HomePageState createState() => _HomePageState();
+}
+
+class _HomePageState extends State<HomePage> {
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(title:const Text('组件曝光测试'),centerTitle: true,),
+      body: _buildBody(),
+    );
+  }
+  
+  Widget _buildBody(){
+    return XXSliverWaterFallFlow(
+      onScrollInit:(int firstIndex, int lastIndex){
+        print('初始化显示的 =========> $firstIndex    $lastIndex');
+      },
+      onScrollEnd:(int firstIndex, int lastIndex){
+        print('滑动结束显示的 =========> $firstIndex    $lastIndex');
+      },
+      itemBuilder: (BuildContext context, int index) {
+        return Container(
+          height:120,
+          color: Colors.red.withAlpha(20 * index),
+          alignment: Alignment.center,
+          child: Text('$index'),
+        );
+      }
+    );
+  }
+}
\ No newline at end of file

example/lib/pages/main_page.dart

+import 'package:example/example_routes.dart';
+import 'package:flutter/material.dart';
+import 'package:ff_annotation_route/ff_annotation_route.dart';
+import 'package:collection/collection.dart';
+import '../example_route.dart';
+import '../example_routes.dart' as example_routes;
+
+@FFRoute(
+  name: 'fluttercandies://mainpage',
+  routeName: 'MainPage',
+)
+class MainPage extends StatelessWidget {
+  MainPage() {
+    final List<String> routeNames = <String>[];
+    routeNames.addAll(example_routes.routeNames);
+    routeNames.remove(Routes.fluttercandiesMainpage);
+    routeNames.remove(Routes.fluttercandiesDemogrouppage);
+    routesGroup.addAll(groupBy<DemoRouteResult, String>(
+        routeNames
+            .map<RouteResult>((String name) => getRouteResult(name: name))
+            .where((RouteResult element) => element.exts != null)
+            .map<DemoRouteResult>((RouteResult e) => DemoRouteResult(e))
+            .toList()
+              ..sort((DemoRouteResult a, DemoRouteResult b) =>
+                  b.group.compareTo(a.group)),
+        (DemoRouteResult x) => x.group));
+  }
+  final Map<String, List<DemoRouteResult>> routesGroup =
+      <String, List<DemoRouteResult>>{};
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        title: const Text('曝光测试'),
+      ),
+      body: ListView.builder(
+        itemBuilder: (BuildContext c, int index) {
+          final String type = routesGroup.keys.toList()[index];
+          return Container(
+              margin: const EdgeInsets.all(20.0),
+              child: GestureDetector(
+                behavior: HitTestBehavior.translucent,
+                child: Column(
+                  crossAxisAlignment: CrossAxisAlignment.start,
+                  children: <Widget>[
+                    Text(
+                      (index + 1).toString() + '.' + type,
+                      //style: TextStyle(inherit: false),
+                    ),
+                    Text(
+                      '$type 曝光测试',
+                      style: const TextStyle(color: Colors.grey),
+                    )
+                  ],
+                ),
+                onTap: () {
+                  Navigator.pushNamed(
+                      context, Routes.fluttercandiesDemogrouppage,
+                      arguments: <String, dynamic>{
+                        'keyValue': routesGroup.entries.toList()[index],
+                      });
+                },
+              ));
+        },
+        itemCount: routesGroup.length,
+      ),
+    );
+  }
+}
+
+@FFRoute(
+  name: 'fluttercandies://demogrouppage',
+  routeName: 'DemoGroupPage',
+)
+class DemoGroupPage extends StatelessWidget {
+  DemoGroupPage({MapEntry<String, List<DemoRouteResult>> keyValue})
+      : routes = keyValue.value
+          ..sort((DemoRouteResult a, DemoRouteResult b) =>
+              a.order.compareTo(b.order)),
+        group = keyValue.key;
+  final List<DemoRouteResult> routes;
+  final String group;
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        title: Text('$group demos'),
+      ),
+      body: ListView.builder(
+        itemBuilder: (BuildContext context, int index) {
+          final DemoRouteResult page = routes[index];
+          return Container(
+            margin: const EdgeInsets.all(20.0),
+            child: GestureDetector(
+              behavior: HitTestBehavior.translucent,
+              child: Column(
+                crossAxisAlignment: CrossAxisAlignment.start,
+                children: <Widget>[
+                  Text(
+                    (index + 1).toString() + '.' + page.routeResult.routeName,
+                    //style: TextStyle(inherit: false),
+                  ),
+                  Text(
+                    page.routeResult.description,
+                    style: const TextStyle(color: Colors.grey),
+                  )
+                ],
+              ),
+              onTap: () {
+                Navigator.pushNamed(context, page.routeResult.name);
+              },
+            ),
+          );
+        },
+        itemCount: routes.length,
+      ),
+    );
+  }
+}
+
+class DemoRouteResult {
+  DemoRouteResult(
+    this.routeResult,
+  )   : order = routeResult.exts['order'] as int,
+        group = routeResult.exts['group'] as String;
+
+  final int order;
+  final String group;
+  final RouteResult routeResult;
+}

example/lib/pages/simple/custom_scrollView_demo.dart

+///
+///  create by zmtzawqlp on 2019/11/19
+///
+import 'dart:math';
+import 'package:ff_annotation_route/ff_annotation_route.dart';
+import 'package:flutter/material.dart';
+import 'package:waterfall_flow/waterfall_flow.dart';
+
+@FFRoute(
+  name: 'fluttercandies://custom_scrollview',
+  routeName: 'custom_scrollview',
+  description: 'show how to build waterfall flow in CustomScrollview.',
+  exts: <String, dynamic>{
+    'group': 'Simple',
+    'order': 1,
+  },
+)
+class CustomScrollviewDemo extends StatefulWidget {
+  @override
+  _CustomScrollviewDemoState createState() => _CustomScrollviewDemoState();
+}
+
+class _CustomScrollviewDemoState extends State<CustomScrollviewDemo> {
+  List<Color> colors = <Color>[];
+  int crossAxisCount = 4;
+  double crossAxisSpacing = 5.0;
+  double mainAxisSpacing = 5.0;
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      body: CustomScrollView(
+        slivers: <Widget>[
+          SliverToBoxAdapter(
+            child: Container(
+              height: 200,
+              color: Colors.red,
+              alignment: Alignment.center,
+              child: const Text(
+                'I\'m other slivers',
+                style: TextStyle(
+                  color: Colors.white,
+                  fontSize: 20,
+                ),
+              ),
+            ),
+          ),
+          SliverWaterfallFlow(
+            gridDelegate: SliverWaterfallFlowDelegateWithFixedCrossAxisCount(
+              crossAxisCount: crossAxisCount,
+              crossAxisSpacing: crossAxisSpacing,
+              mainAxisSpacing: mainAxisSpacing,
+              collectGarbage: (List<int> garbages) {
+                print('collect garbage : $garbages');
+              },
+              viewportBuilder: (int firstIndex, int lastIndex) {
+                print('viewport : [$firstIndex,$lastIndex]');
+              },
+            ),
+            delegate: SliverChildBuilderDelegate((BuildContext c, int index) {
+              final Color color = getRandomColor(index);
+              return Container(
+                decoration: BoxDecoration(
+                    border: Border.all(color: Colors.black),
+                    color: getRandomColor(index)),
+                alignment: Alignment.center,
+                child: Text(
+                  '$index',
+                  style: TextStyle(
+                      color: color.computeLuminance() < 0.5
+                          ? Colors.white
+                          : Colors.black),
+                ),
+                //height: index == 5 ? 1500.0 : 100.0,
+                height: ((index % 3) + 1) * 100.0,
+              );
+            }),
+          )
+        ],
+      ),
+      floatingActionButton: FloatingActionButton(
+        onPressed: () {
+          setState(() {
+            crossAxisCount++;
+            //mainAxisSpacing+=5.0;
+            //crossAxisSpacing+=5.0;
+          });
+        },
+        child: const Icon(Icons.add),
+      ),
+    );
+  }
+
+  Color getRandomColor(int index) {
+    if (index >= colors.length) {
+      colors.add(Color.fromARGB(255, Random.secure().nextInt(255),
+          Random.secure().nextInt(255), Random.secure().nextInt(255)));
+    }
+
+    return colors[index];
+  }
+}

example/lib/pages/simple/random_sized_demo.dart

+///
+///  create by zmtzawqlp on 2019/11/19
+///
+import 'dart:math';
+import 'package:ff_annotation_route/ff_annotation_route.dart';
+import 'package:flutter/material.dart';
+import 'package:waterfall_flow/waterfall_flow.dart';
+
+@FFRoute(
+  name: 'fluttercandies://random-sized',
+  routeName: 'random-sized',
+  description: 'show how to build random-sized item with waterfall flow list.',
+  exts: <String, dynamic>{
+    'group': 'Simple',
+    'order': 0,
+  },
+)
+class RandomSizedDemo extends StatefulWidget {
+  @override
+  _RandomSizedDemoState createState() => _RandomSizedDemoState();
+}
+
+class _RandomSizedDemoState extends State<RandomSizedDemo> {
+  List<Color> colors = <Color>[];
+  int crossAxisCount = 4;
+  double crossAxisSpacing = 5.0;
+  double mainAxisSpacing = 5.0;
+  TextDirection textDirection = TextDirection.ltr;
+  int length = 100;
+  ScrollController controller = ScrollController();
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      body: Directionality(
+        textDirection: textDirection,
+        child: WaterfallFlow.builder(
+          //cacheExtent: 0.0,
+          //reverse: true,
+          padding: const EdgeInsets.all(5.0),
+          gridDelegate: SliverWaterfallFlowDelegateWithFixedCrossAxisCount(
+            crossAxisCount: crossAxisCount,
+            crossAxisSpacing: crossAxisSpacing,
+            mainAxisSpacing: mainAxisSpacing,
+            // collectGarbage: (List<int> garbages) {
+            //   print('collect garbage : $garbages');
+            // },
+            // viewportBuilder: (int firstIndex, int lastIndex) {
+            //   print('viewport : [$firstIndex,$lastIndex]');
+            // },
+          ),
+          itemBuilder: (BuildContext c, int index) {
+            final Color color = getRandomColor(index);
+
+            return Container(
+              decoration: BoxDecoration(
+                  border: Border.all(color: Colors.black),
+                  color: getRandomColor(index)),
+              alignment: Alignment.center,
+              child: Text(
+                '$index ' + 'TestString' * 10 * (index % 3 + 1),
+                style: TextStyle(
+                    color: color.computeLuminance() < 0.5
+                        ? Colors.white
+                        : Colors.black),
+              ),
+              //height: ((index % 3) + 1) * 100.0,
+            );
+          },
+          //itemCount: 19,
+          itemCount: length,
+        ),
+      ),
+      floatingActionButton: FloatingActionButton(
+        onPressed: () {
+          setState(() {
+            // if (textDirection == TextDirection.ltr) {
+            //   textDirection = TextDirection.rtl;
+            // } else {
+            //   textDirection = TextDirection.ltr;
+            // }
+            //length=0;
+            crossAxisCount++;
+            //mainAxisSpacing += 5.0;
+            //crossAxisSpacing+=5.0;
+          });
+        },
+        child: const Icon(Icons.add),
+      ),
+    );
+  }
+
+  Color getRandomColor(int index) {
+    if (index >= colors.length) {
+      colors.add(Color.fromARGB(255, Random.secure().nextInt(255),
+          Random.secure().nextInt(255), Random.secure().nextInt(255)));
+    }
+
+    return colors[index];
+  }
+}

example/macos/.gitignore

+# Flutter-related
+**/Flutter/ephemeral/
+**/Pods/
+
+# Xcode-related
+**/xcuserdata/

example/macos/Flutter/Flutter-Debug.xcconfig

+#include "Pods/Target Support Files/Pods-Runner/Pods-Runner.debug.xcconfig"
+#include "ephemeral/Flutter-Generated.xcconfig"

example/macos/Flutter/Flutter-Release.xcconfig

+#include "Pods/Target Support Files/Pods-Runner/Pods-Runner.release.xcconfig"
+#include "ephemeral/Flutter-Generated.xcconfig"

example/macos/Flutter/GeneratedPluginRegistrant.swift

+//
+//  Generated file. Do not edit.
+//
+
+import FlutterMacOS
+import Foundation
+
+import path_provider_macos
+
+func RegisterGeneratedPlugins(registry: FlutterPluginRegistry) {
+  PathProviderPlugin.register(with: registry.registrar(forPlugin: "PathProviderPlugin"))
+}

example/macos/Podfile

+platform :osx, '10.11'
+
+# CocoaPods analytics sends network stats synchronously affecting flutter build latency.
+ENV['COCOAPODS_DISABLE_STATS'] = 'true'
+
+project 'Runner', {
+  'Debug' => :debug,
+  'Profile' => :release,
+  'Release' => :release,
+}
+
+def parse_KV_file(file, separator='=')
+  file_abs_path = File.expand_path(file)
+  if !File.exists? file_abs_path
+    return [];
+  end
+  pods_ary = []
+  skip_line_start_symbols = ["#", "/"]
+  File.foreach(file_abs_path) { |line|
+      next if skip_line_start_symbols.any? { |symbol| line =~ /^\s*#{symbol}/ }
+      plugin = line.split(pattern=separator)
+      if plugin.length == 2
+        podname = plugin[0].strip()
+        path = plugin[1].strip()
+        podpath = File.expand_path("#{path}", file_abs_path)
+        pods_ary.push({:name => podname, :path => podpath});
+      else
+        puts "Invalid plugin specification: #{line}"
+      end
+  }
+  return pods_ary
+end
+
+def pubspec_supports_macos(file)
+  file_abs_path = File.expand_path(file)
+  if !File.exists? file_abs_path
+    return false;
+  end
+  File.foreach(file_abs_path) { |line|
+    return true if line =~ /^\s*macos:/
+  }
+  return false
+end
+
+target 'Runner' do
+  use_frameworks!
+  use_modular_headers!
+
+  # Prepare symlinks folder. We use symlinks to avoid having Podfile.lock
+  # referring to absolute paths on developers' machines.
+  ephemeral_dir = File.join('Flutter', 'ephemeral')
+  symlink_dir = File.join(ephemeral_dir, '.symlinks')
+  symlink_plugins_dir = File.join(symlink_dir, 'plugins')
+  system("rm -rf #{symlink_dir}")
+  system("mkdir -p #{symlink_plugins_dir}")
+
+  # Flutter Pods
+  generated_xcconfig = parse_KV_file(File.join(ephemeral_dir, 'Flutter-Generated.xcconfig'))
+  if generated_xcconfig.empty?
+    puts "Flutter-Generated.xcconfig must exist. If you're running pod install manually, make sure flutter packages get is executed first."
+  end
+  generated_xcconfig.map { |p|
+    if p[:name] == 'FLUTTER_FRAMEWORK_DIR'
+      symlink = File.join(symlink_dir, 'flutter')
+      File.symlink(File.dirname(p[:path]), symlink)
+      pod 'FlutterMacOS', :path => File.join(symlink, File.basename(p[:path]))
+    end
+  }
+
+  # Plugin Pods
+  plugin_pods = parse_KV_file('../.flutter-plugins')
+  plugin_pods.map { |p|
+    symlink = File.join(symlink_plugins_dir, p[:name])
+    File.symlink(p[:path], symlink)
+    if pubspec_supports_macos(File.join(symlink, 'pubspec.yaml'))
+      pod p[:name], :path => File.join(symlink, 'macos')
+    end
+  }
+end
+
+# Prevent Cocoapods from embedding a second Flutter framework and causing an error with the new Xcode build system.
+install! 'cocoapods', :disable_input_output_paths => true

example/macos/Podfile.lock

+PODS:
+  - FlutterMacOS (1.0.0)
+  - path_provider (0.0.1)
+  - path_provider_macos (0.0.1):
+    - FlutterMacOS
+
+DEPENDENCIES:
+  - FlutterMacOS (from `Flutter/ephemeral/.symlinks/flutter/darwin-x64`)
+  - path_provider (from `Flutter/ephemeral/.symlinks/plugins/path_provider/macos`)
+  - path_provider_macos (from `Flutter/ephemeral/.symlinks/plugins/path_provider_macos/macos`)
+
+EXTERNAL SOURCES:
+  FlutterMacOS:
+    :path: Flutter/ephemeral/.symlinks/flutter/darwin-x64
+  path_provider:
+    :path: Flutter/ephemeral/.symlinks/plugins/path_provider/macos
+  path_provider_macos:
+    :path: Flutter/ephemeral/.symlinks/plugins/path_provider_macos/macos
+
+SPEC CHECKSUMS:
+  FlutterMacOS: 15bea8a44d2fa024068daa0140371c020b4b6ff9
+  path_provider: e0848572d1d38b9a7dd099e79cf83f5b7e2cde9f
+  path_provider_macos: a0a3fd666cb7cd0448e936fb4abad4052961002b
+
+PODFILE CHECKSUM: d8ba9b3e9e93c62c74a660b46c6fcb09f03991a7
+
+COCOAPODS: 1.9.3

example/macos/Runner.xcodeproj/project.pbxproj

+// !$*UTF8*$!
+{
+	archiveVersion = 1;
+	classes = {
+	};
+	objectVersion = 51;
+	objects = {
+
+/* Begin PBXAggregateTarget section */
+		33CC111A2044C6BA0003C045 /* Flutter Assemble */ = {
+			isa = PBXAggregateTarget;
+			buildConfigurationList = 33CC111B2044C6BA0003C045 /* Build configuration list for PBXAggregateTarget "Flutter Assemble" */;
+			buildPhases = (
+				33CC111E2044C6BF0003C045 /* ShellScript */,
+			);
+			dependencies = (
+			);
+			name = "Flutter Assemble";
+			productName = FLX;
+		};
+/* End PBXAggregateTarget section */
+
+/* Begin PBXBuildFile section */
+		335BBD1B22A9A15E00E9071D /* GeneratedPluginRegistrant.swift in Sources */ = {isa = PBXBuildFile; fileRef = 335BBD1A22A9A15E00E9071D /* GeneratedPluginRegistrant.swift */; };
+		33CC10F12044A3C60003C045 /* AppDelegate.swift in Sources */ = {isa = PBXBuildFile; fileRef = 33CC10F02044A3C60003C045 /* AppDelegate.swift */; };
+		33CC10F32044A3C60003C045 /* Assets.xcassets in Resources */ = {isa = PBXBuildFile; fileRef = 33CC10F22044A3C60003C045 /* Assets.xcassets */; };
+		33CC10F62044A3C60003C045 /* MainMenu.xib in Resources */ = {isa = PBXBuildFile; fileRef = 33CC10F42044A3C60003C045 /* MainMenu.xib */; };
+		33CC11132044BFA00003C045 /* MainFlutterWindow.swift in Sources */ = {isa = PBXBuildFile; fileRef = 33CC11122044BFA00003C045 /* MainFlutterWindow.swift */; };
+		33D1A10422148B71006C7A3E /* FlutterMacOS.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 33D1A10322148B71006C7A3E /* FlutterMacOS.framework */; };
+		33D1A10522148B93006C7A3E /* FlutterMacOS.framework in Bundle Framework */ = {isa = PBXBuildFile; fileRef = 33D1A10322148B71006C7A3E /* FlutterMacOS.framework */; settings = {ATTRIBUTES = (CodeSignOnCopy, RemoveHeadersOnCopy, ); }; };
+		5418B21A951BB5A69941CC01 /* Pods_Runner.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 0CB9E840061A2185D4F3FF80 /* Pods_Runner.framework */; };
+		D73912F022F37F9E000D13A0 /* App.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = D73912EF22F37F9E000D13A0 /* App.framework */; };
+		D73912F222F3801D000D13A0 /* App.framework in Bundle Framework */ = {isa = PBXBuildFile; fileRef = D73912EF22F37F9E000D13A0 /* App.framework */; settings = {ATTRIBUTES = (CodeSignOnCopy, RemoveHeadersOnCopy, ); }; };
+/* End PBXBuildFile section */
+
+/* Begin PBXContainerItemProxy section */
+		33CC111F2044C79F0003C045 /* PBXContainerItemProxy */ = {
+			isa = PBXContainerItemProxy;
+			containerPortal = 33CC10E52044A3C60003C045 /* Project object */;
+			proxyType = 1;
+			remoteGlobalIDString = 33CC111A2044C6BA0003C045;
+			remoteInfo = FLX;
+		};
+/* End PBXContainerItemProxy section */
+
+/* Begin PBXCopyFilesBuildPhase section */
+		33CC110E2044A8840003C045 /* Bundle Framework */ = {
+			isa = PBXCopyFilesBuildPhase;
+			buildActionMask = 2147483647;
+			dstPath = "";
+			dstSubfolderSpec = 10;
+			files = (
+				D73912F222F3801D000D13A0 /* App.framework in Bundle Framework */,
+				33D1A10522148B93006C7A3E /* FlutterMacOS.framework in Bundle Framework */,
+			);
+			name = "Bundle Framework";
+			runOnlyForDeploymentPostprocessing = 0;
+		};
+/* End PBXCopyFilesBuildPhase section */
+
+/* Begin PBXFileReference section */
+		0CB9E840061A2185D4F3FF80 /* Pods_Runner.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = Pods_Runner.framework; sourceTree = BUILT_PRODUCTS_DIR; };
+		2CAEAF66C25BB426870E3329 /* Pods-Runner.profile.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = "Pods-Runner.profile.xcconfig"; path = "Target Support Files/Pods-Runner/Pods-Runner.profile.xcconfig"; sourceTree = "<group>"; };
+		333000ED22D3DE5D00554162 /* Warnings.xcconfig */ = {isa = PBXFileReference; lastKnownFileType = text.xcconfig; path = Warnings.xcconfig; sourceTree = "<group>"; };
+		335BBD1A22A9A15E00E9071D /* GeneratedPluginRegistrant.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = GeneratedPluginRegistrant.swift; sourceTree = "<group>"; };
+		33CC10ED2044A3C60003C045 /* example.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = example.app; sourceTree = BUILT_PRODUCTS_DIR; };
+		33CC10F02044A3C60003C045 /* AppDelegate.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AppDelegate.swift; sourceTree = "<group>"; };
+		33CC10F22044A3C60003C045 /* Assets.xcassets */ = {isa = PBXFileReference; lastKnownFileType = folder.assetcatalog; name = Assets.xcassets; path = Runner/Assets.xcassets; sourceTree = "<group>"; };
+		33CC10F52044A3C60003C045 /* Base */ = {isa = PBXFileReference; lastKnownFileType = file.xib; name = Base; path = Base.lproj/MainMenu.xib; sourceTree = "<group>"; };
+		33CC10F72044A3C60003C045 /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; name = Info.plist; path = Runner/Info.plist; sourceTree = "<group>"; };
+		33CC11122044BFA00003C045 /* MainFlutterWindow.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MainFlutterWindow.swift; sourceTree = "<group>"; };
+		33CEB47222A05771004F2AC0 /* Flutter-Debug.xcconfig */ = {isa = PBXFileReference; lastKnownFileType = text.xcconfig; path = "Flutter-Debug.xcconfig"; sourceTree = "<group>"; };
+		33CEB47422A05771004F2AC0 /* Flutter-Release.xcconfig */ = {isa = PBXFileReference; lastKnownFileType = text.xcconfig; path = "Flutter-Release.xcconfig"; sourceTree = "<group>"; };
+		33CEB47722A0578A004F2AC0 /* Flutter-Generated.xcconfig */ = {isa = PBXFileReference; lastKnownFileType = text.xcconfig; name = "Flutter-Generated.xcconfig"; path = "ephemeral/Flutter-Generated.xcconfig"; sourceTree = "<group>"; };
+		33D1A10322148B71006C7A3E /* FlutterMacOS.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = FlutterMacOS.framework; path = Flutter/ephemeral/FlutterMacOS.framework; sourceTree = SOURCE_ROOT; };
+		33E51913231747F40026EE4D /* DebugProfile.entitlements */ = {isa = PBXFileReference; lastKnownFileType = text.plist.entitlements; path = DebugProfile.entitlements; sourceTree = "<group>"; };
+		33E51914231749380026EE4D /* Release.entitlements */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.plist.entitlements; path = Release.entitlements; sourceTree = "<group>"; };
+		33E5194F232828860026EE4D /* AppInfo.xcconfig */ = {isa = PBXFileReference; lastKnownFileType = text.xcconfig; path = AppInfo.xcconfig; sourceTree = "<group>"; };
+		39458616FA7CAA5A684D151C /* Pods-Runner.debug.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = "Pods-Runner.debug.xcconfig"; path = "Target Support Files/Pods-Runner/Pods-Runner.debug.xcconfig"; sourceTree = "<group>"; };
+		4FE541B9FF3AD544B9096546 /* Pods-Runner.release.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = "Pods-Runner.release.xcconfig"; path = "Target Support Files/Pods-Runner/Pods-Runner.release.xcconfig"; sourceTree = "<group>"; };
+		7AFA3C8E1D35360C0083082E /* Release.xcconfig */ = {isa = PBXFileReference; lastKnownFileType = text.xcconfig; path = Release.xcconfig; sourceTree = "<group>"; };
+		9740EEB21CF90195004384FC /* Debug.xcconfig */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.xcconfig; path = Debug.xcconfig; sourceTree = "<group>"; };
+		D73912EF22F37F9E000D13A0 /* App.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = App.framework; path = Flutter/ephemeral/App.framework; sourceTree = SOURCE_ROOT; };
+/* End PBXFileReference section */
+
+/* Begin PBXFrameworksBuildPhase section */
+		33CC10EA2044A3C60003C045 /* Frameworks */ = {
+			isa = PBXFrameworksBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+				D73912F022F37F9E000D13A0 /* App.framework in Frameworks */,
+				33D1A10422148B71006C7A3E /* FlutterMacOS.framework in Frameworks */,
+				5418B21A951BB5A69941CC01 /* Pods_Runner.framework in Frameworks */,
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+		};
+/* End PBXFrameworksBuildPhase section */
+
+/* Begin PBXGroup section */
+		26C1D6710B9F7CBA3EA7A12D /* Pods */ = {
+			isa = PBXGroup;
+			children = (
+				39458616FA7CAA5A684D151C /* Pods-Runner.debug.xcconfig */,
+				4FE541B9FF3AD544B9096546 /* Pods-Runner.release.xcconfig */,
+				2CAEAF66C25BB426870E3329 /* Pods-Runner.profile.xcconfig */,
+			);
+			name = Pods;
+			path = Pods;
+			sourceTree = "<group>";
+		};
+		33BA886A226E78AF003329D5 /* Configs */ = {
+			isa = PBXGroup;
+			children = (
+				33E5194F232828860026EE4D /* AppInfo.xcconfig */,
+				9740EEB21CF90195004384FC /* Debug.xcconfig */,
+				7AFA3C8E1D35360C0083082E /* Release.xcconfig */,
+				333000ED22D3DE5D00554162 /* Warnings.xcconfig */,
+			);
+			path = Configs;
+			sourceTree = "<group>";
+		};
+		33CC10E42044A3C60003C045 = {
+			isa = PBXGroup;
+			children = (
+				33FAB671232836740065AC1E /* Runner */,
+				33CEB47122A05771004F2AC0 /* Flutter */,
+				33CC10EE2044A3C60003C045 /* Products */,
+				D73912EC22F37F3D000D13A0 /* Frameworks */,
+				26C1D6710B9F7CBA3EA7A12D /* Pods */,
+			);
+			sourceTree = "<group>";
+		};
+		33CC10EE2044A3C60003C045 /* Products */ = {
+			isa = PBXGroup;
+			children = (
+				33CC10ED2044A3C60003C045 /* example.app */,
+			);
+			name = Products;
+			sourceTree = "<group>";
+		};
+		33CC11242044D66E0003C045 /* Resources */ = {
+			isa = PBXGroup;
+			children = (
+				33CC10F22044A3C60003C045 /* Assets.xcassets */,
+				33CC10F42044A3C60003C045 /* MainMenu.xib */,
+				33CC10F72044A3C60003C045 /* Info.plist */,
+			);
+			name = Resources;
+			path = ..;
+			sourceTree = "<group>";
+		};
+		33CEB47122A05771004F2AC0 /* Flutter */ = {
+			isa = PBXGroup;
+			children = (
+				335BBD1A22A9A15E00E9071D /* GeneratedPluginRegistrant.swift */,
+				33CEB47222A05771004F2AC0 /* Flutter-Debug.xcconfig */,
+				33CEB47422A05771004F2AC0 /* Flutter-Release.xcconfig */,
+				33CEB47722A0578A004F2AC0 /* Flutter-Generated.xcconfig */,
+				D73912EF22F37F9E000D13A0 /* App.framework */,
+				33D1A10322148B71006C7A3E /* FlutterMacOS.framework */,
+			);
+			path = Flutter;
+			sourceTree = "<group>";
+		};
+		33FAB671232836740065AC1E /* Runner */ = {
+			isa = PBXGroup;
+			children = (
+				33CC10F02044A3C60003C045 /* AppDelegate.swift */,
+				33CC11122044BFA00003C045 /* MainFlutterWindow.swift */,
+				33E51913231747F40026EE4D /* DebugProfile.entitlements */,
+				33E51914231749380026EE4D /* Release.entitlements */,
+				33CC11242044D66E0003C045 /* Resources */,
+				33BA886A226E78AF003329D5 /* Configs */,
+			);
+			path = Runner;
+			sourceTree = "<group>";
+		};
+		D73912EC22F37F3D000D13A0 /* Frameworks */ = {
+			isa = PBXGroup;
+			children = (
+				0CB9E840061A2185D4F3FF80 /* Pods_Runner.framework */,
+			);
+			name = Frameworks;
+			sourceTree = "<group>";
+		};
+/* End PBXGroup section */
+
+/* Begin PBXNativeTarget section */
+		33CC10EC2044A3C60003C045 /* Runner */ = {
+			isa = PBXNativeTarget;
+			buildConfigurationList = 33CC10FB2044A3C60003C045 /* Build configuration list for PBXNativeTarget "Runner" */;
+			buildPhases = (
+				5AB4BCFF93F692834DBCD171 /* [CP] Check Pods Manifest.lock */,
+				33CC10E92044A3C60003C045 /* Sources */,
+				33CC10EA2044A3C60003C045 /* Frameworks */,
+				33CC10EB2044A3C60003C045 /* Resources */,
+				33CC110E2044A8840003C045 /* Bundle Framework */,
+				3399D490228B24CF009A79C7 /* ShellScript */,
+				76CA9536FF591539E2792178 /* [CP] Embed Pods Frameworks */,
+			);
+			buildRules = (
+			);
+			dependencies = (
+				33CC11202044C79F0003C045 /* PBXTargetDependency */,
+			);
+			name = Runner;
+			productName = Runner;
+			productReference = 33CC10ED2044A3C60003C045 /* example.app */;
+			productType = "com.apple.product-type.application";
+		};
+/* End PBXNativeTarget section */
+
+/* Begin PBXProject section */
+		33CC10E52044A3C60003C045 /* Project object */ = {
+			isa = PBXProject;
+			attributes = {
+				LastSwiftUpdateCheck = 0920;
+				LastUpgradeCheck = 0930;
+				ORGANIZATIONNAME = "The Flutter Authors";
+				TargetAttributes = {
+					33CC10EC2044A3C60003C045 = {
+						CreatedOnToolsVersion = 9.2;
+						LastSwiftMigration = 1100;
+						ProvisioningStyle = Automatic;
+						SystemCapabilities = {
+							com.apple.Sandbox = {
+								enabled = 1;
+							};
+						};
+					};
+					33CC111A2044C6BA0003C045 = {
+						CreatedOnToolsVersion = 9.2;
+						ProvisioningStyle = Manual;
+					};
+				};
+			};
+			buildConfigurationList = 33CC10E82044A3C60003C045 /* Build configuration list for PBXProject "Runner" */;
+			compatibilityVersion = "Xcode 8.0";
+			developmentRegion = en;
+			hasScannedForEncodings = 0;
+			knownRegions = (
+				en,
+				Base,
+			);
+			mainGroup = 33CC10E42044A3C60003C045;
+			productRefGroup = 33CC10EE2044A3C60003C045 /* Products */;
+			projectDirPath = "";
+			projectRoot = "";
+			targets = (
+				33CC10EC2044A3C60003C045 /* Runner */,
+				33CC111A2044C6BA0003C045 /* Flutter Assemble */,
+			);
+		};
+/* End PBXProject section */
+
+/* Begin PBXResourcesBuildPhase section */
+		33CC10EB2044A3C60003C045 /* Resources */ = {
+			isa = PBXResourcesBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+				33CC10F32044A3C60003C045 /* Assets.xcassets in Resources */,
+				33CC10F62044A3C60003C045 /* MainMenu.xib in Resources */,
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+		};
+/* End PBXResourcesBuildPhase section */
+
+/* Begin PBXShellScriptBuildPhase section */
+		3399D490228B24CF009A79C7 /* ShellScript */ = {
+			isa = PBXShellScriptBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+			);
+			inputFileListPaths = (
+			);
+			inputPaths = (
+			);
+			outputFileListPaths = (
+			);
+			outputPaths = (
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+			shellPath = /bin/sh;
+			shellScript = "echo \"$PRODUCT_NAME.app\" > \"$PROJECT_DIR\"/Flutter/ephemeral/.app_filename\n";
+		};
+		33CC111E2044C6BF0003C045 /* ShellScript */ = {
+			isa = PBXShellScriptBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+			);
+			inputFileListPaths = (
+				Flutter/ephemeral/FlutterInputs.xcfilelist,
+			);
+			inputPaths = (
+				Flutter/ephemeral/tripwire,
+			);
+			outputFileListPaths = (
+				Flutter/ephemeral/FlutterOutputs.xcfilelist,
+			);
+			outputPaths = (
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+			shellPath = /bin/sh;
+			shellScript = "\"$FLUTTER_ROOT\"/packages/flutter_tools/bin/macos_assemble.sh && touch Flutter/ephemeral/tripwire";
+		};
+		5AB4BCFF93F692834DBCD171 /* [CP] Check Pods Manifest.lock */ = {
+			isa = PBXShellScriptBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+			);
+			inputFileListPaths = (
+			);
+			inputPaths = (
+				"${PODS_PODFILE_DIR_PATH}/Podfile.lock",
+				"${PODS_ROOT}/Manifest.lock",
+			);
+			name = "[CP] Check Pods Manifest.lock";
+			outputFileListPaths = (
+			);
+			outputPaths = (
+				"$(DERIVED_FILE_DIR)/Pods-Runner-checkManifestLockResult.txt",
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+			shellPath = /bin/sh;
+			shellScript = "diff \"${PODS_PODFILE_DIR_PATH}/Podfile.lock\" \"${PODS_ROOT}/Manifest.lock\" > /dev/null\nif [ $? != 0 ] ; then\n    # print error to STDERR\n    echo \"error: The sandbox is not in sync with the Podfile.lock. Run 'pod install' or update your CocoaPods installation.\" >&2\n    exit 1\nfi\n# This output is used by Xcode 'outputs' to avoid re-running this script phase.\necho \"SUCCESS\" > \"${SCRIPT_OUTPUT_FILE_0}\"\n";
+			showEnvVarsInLog = 0;
+		};
+		76CA9536FF591539E2792178 /* [CP] Embed Pods Frameworks */ = {
+			isa = PBXShellScriptBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+			);
+			inputFileListPaths = (
+			);
+			name = "[CP] Embed Pods Frameworks";
+			outputFileListPaths = (
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+			shellPath = /bin/sh;
+			shellScript = "\"${PODS_ROOT}/Target Support Files/Pods-Runner/Pods-Runner-frameworks.sh\"\n";
+			showEnvVarsInLog = 0;
+		};
+/* End PBXShellScriptBuildPhase section */
+
+/* Begin PBXSourcesBuildPhase section */
+		33CC10E92044A3C60003C045 /* Sources */ = {
+			isa = PBXSourcesBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+				33CC11132044BFA00003C045 /* MainFlutterWindow.swift in Sources */,
+				33CC10F12044A3C60003C045 /* AppDelegate.swift in Sources */,
+				335BBD1B22A9A15E00E9071D /* GeneratedPluginRegistrant.swift in Sources */,
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+		};
+/* End PBXSourcesBuildPhase section */
+
+/* Begin PBXTargetDependency section */
+		33CC11202044C79F0003C045 /* PBXTargetDependency */ = {
+			isa = PBXTargetDependency;
+			target = 33CC111A2044C6BA0003C045 /* Flutter Assemble */;
+			targetProxy = 33CC111F2044C79F0003C045 /* PBXContainerItemProxy */;
+		};
+/* End PBXTargetDependency section */
+
+/* Begin PBXVariantGroup section */
+		33CC10F42044A3C60003C045 /* MainMenu.xib */ = {
+			isa = PBXVariantGroup;
+			children = (
+				33CC10F52044A3C60003C045 /* Base */,
+			);
+			name = MainMenu.xib;
+			path = Runner;
+			sourceTree = "<group>";
+		};
+/* End PBXVariantGroup section */
+
+/* Begin XCBuildConfiguration section */
+		338D0CE9231458BD00FA5F75 /* Profile */ = {
+			isa = XCBuildConfiguration;
+			baseConfigurationReference = 7AFA3C8E1D35360C0083082E /* Release.xcconfig */;
+			buildSettings = {
+				ALWAYS_SEARCH_USER_PATHS = NO;
+				CLANG_ANALYZER_NONNULL = YES;
+				CLANG_ANALYZER_NUMBER_OBJECT_CONVERSION = YES_AGGRESSIVE;
+				CLANG_CXX_LANGUAGE_STANDARD = "gnu++14";
+				CLANG_CXX_LIBRARY = "libc++";
+				CLANG_ENABLE_MODULES = YES;
+				CLANG_ENABLE_OBJC_ARC = YES;
+				CLANG_WARN_BLOCK_CAPTURE_AUTORELEASING = YES;
+				CLANG_WARN_BOOL_CONVERSION = YES;
+				CLANG_WARN_CONSTANT_CONVERSION = YES;
+				CLANG_WARN_DEPRECATED_OBJC_IMPLEMENTATIONS = YES;
+				CLANG_WARN_DIRECT_OBJC_ISA_USAGE = YES_ERROR;
+				CLANG_WARN_DOCUMENTATION_COMMENTS = YES;
+				CLANG_WARN_EMPTY_BODY = YES;
+				CLANG_WARN_ENUM_CONVERSION = YES;
+				CLANG_WARN_INFINITE_RECURSION = YES;
+				CLANG_WARN_INT_CONVERSION = YES;
+				CLANG_WARN_NON_LITERAL_NULL_CONVERSION = YES;
+				CLANG_WARN_OBJC_LITERAL_CONVERSION = YES;
+				CLANG_WARN_OBJC_ROOT_CLASS = YES_ERROR;
+				CLANG_WARN_RANGE_LOOP_ANALYSIS = YES;
+				CLANG_WARN_SUSPICIOUS_MOVE = YES;
+				CODE_SIGN_IDENTITY = "-";
+				COPY_PHASE_STRIP = NO;
+				DEBUG_INFORMATION_FORMAT = "dwarf-with-dsym";
+				ENABLE_NS_ASSERTIONS = NO;
+				ENABLE_STRICT_OBJC_MSGSEND = YES;
+				GCC_C_LANGUAGE_STANDARD = gnu11;
+				GCC_NO_COMMON_BLOCKS = YES;
+				GCC_WARN_64_TO_32_BIT_CONVERSION = YES;
+				GCC_WARN_ABOUT_RETURN_TYPE = YES_ERROR;
+				GCC_WARN_UNINITIALIZED_AUTOS = YES_AGGRESSIVE;
+				GCC_WARN_UNUSED_FUNCTION = YES;
+				GCC_WARN_UNUSED_VARIABLE = YES;
+				MACOSX_DEPLOYMENT_TARGET = 10.11;
+				MTL_ENABLE_DEBUG_INFO = NO;
+				SDKROOT = macosx;
+				SWIFT_COMPILATION_MODE = wholemodule;
+				SWIFT_OPTIMIZATION_LEVEL = "-O";
+			};
+			name = Profile;
+		};
+		338D0CEA231458BD00FA5F75 /* Profile */ = {
+			isa = XCBuildConfiguration;
+			baseConfigurationReference = 33E5194F232828860026EE4D /* AppInfo.xcconfig */;
+			buildSettings = {
+				ASSETCATALOG_COMPILER_APPICON_NAME = AppIcon;
+				CLANG_ENABLE_MODULES = YES;
+				CODE_SIGN_ENTITLEMENTS = Runner/DebugProfile.entitlements;
+				CODE_SIGN_STYLE = Automatic;
+				COMBINE_HIDPI_IMAGES = YES;
+				FRAMEWORK_SEARCH_PATHS = (
+					"$(inherited)",
+					"$(PROJECT_DIR)/Flutter/ephemeral",
+				);
+				INFOPLIST_FILE = Runner/Info.plist;
+				LD_RUNPATH_SEARCH_PATHS = (
+					"$(inherited)",
+					"@executable_path/../Frameworks",
+				);
+				PROVISIONING_PROFILE_SPECIFIER = "";
+				SWIFT_VERSION = 5.0;
+			};
+			name = Profile;
+		};
+		338D0CEB231458BD00FA5F75 /* Profile */ = {
+			isa = XCBuildConfiguration;
+			buildSettings = {
+				CODE_SIGN_STYLE = Manual;
+				PRODUCT_NAME = "$(TARGET_NAME)";
+			};
+			name = Profile;
+		};
+		33CC10F92044A3C60003C045 /* Debug */ = {
+			isa = XCBuildConfiguration;
+			baseConfigurationReference = 9740EEB21CF90195004384FC /* Debug.xcconfig */;
+			buildSettings = {
+				ALWAYS_SEARCH_USER_PATHS = NO;
+				CLANG_ANALYZER_NONNULL = YES;
+				CLANG_ANALYZER_NUMBER_OBJECT_CONVERSION = YES_AGGRESSIVE;
+				CLANG_CXX_LANGUAGE_STANDARD = "gnu++14";
+				CLANG_CXX_LIBRARY = "libc++";
+				CLANG_ENABLE_MODULES = YES;
+				CLANG_ENABLE_OBJC_ARC = YES;
+				CLANG_WARN_BLOCK_CAPTURE_AUTORELEASING = YES;
+				CLANG_WARN_BOOL_CONVERSION = YES;
+				CLANG_WARN_CONSTANT_CONVERSION = YES;
+				CLANG_WARN_DEPRECATED_OBJC_IMPLEMENTATIONS = YES;
+				CLANG_WARN_DIRECT_OBJC_ISA_USAGE = YES_ERROR;
+				CLANG_WARN_DOCUMENTATION_COMMENTS = YES;
+				CLANG_WARN_EMPTY_BODY = YES;
+				CLANG_WARN_ENUM_CONVERSION = YES;
+				CLANG_WARN_INFINITE_RECURSION = YES;
+				CLANG_WARN_INT_CONVERSION = YES;
+				CLANG_WARN_NON_LITERAL_NULL_CONVERSION = YES;
+				CLANG_WARN_OBJC_LITERAL_CONVERSION = YES;
+				CLANG_WARN_OBJC_ROOT_CLASS = YES_ERROR;
+				CLANG_WARN_RANGE_LOOP_ANALYSIS = YES;
+				CLANG_WARN_SUSPICIOUS_MOVE = YES;
+				CODE_SIGN_IDENTITY = "-";
+				COPY_PHASE_STRIP = NO;
+				DEBUG_INFORMATION_FORMAT = dwarf;
+				ENABLE_STRICT_OBJC_MSGSEND = YES;
+				ENABLE_TESTABILITY = YES;
+				GCC_C_LANGUAGE_STANDARD = gnu11;
+				GCC_DYNAMIC_NO_PIC = NO;
+				GCC_NO_COMMON_BLOCKS = YES;
+				GCC_OPTIMIZATION_LEVEL = 0;
+				GCC_PREPROCESSOR_DEFINITIONS = (
+					"DEBUG=1",
+					"$(inherited)",
+				);
+				GCC_WARN_64_TO_32_BIT_CONVERSION = YES;
+				GCC_WARN_ABOUT_RETURN_TYPE = YES_ERROR;
+				GCC_WARN_UNINITIALIZED_AUTOS = YES_AGGRESSIVE;
+				GCC_WARN_UNUSED_FUNCTION = YES;
+				GCC_WARN_UNUSED_VARIABLE = YES;
+				MACOSX_DEPLOYMENT_TARGET = 10.11;
+				MTL_ENABLE_DEBUG_INFO = YES;
+				ONLY_ACTIVE_ARCH = YES;
+				SDKROOT = macosx;
+				SWIFT_ACTIVE_COMPILATION_CONDITIONS = DEBUG;
+				SWIFT_OPTIMIZATION_LEVEL = "-Onone";
+			};
+			name = Debug;
+		};
+		33CC10FA2044A3C60003C045 /* Release */ = {
+			isa = XCBuildConfiguration;
+			baseConfigurationReference = 7AFA3C8E1D35360C0083082E /* Release.xcconfig */;
+			buildSettings = {
+				ALWAYS_SEARCH_USER_PATHS = NO;
+				CLANG_ANALYZER_NONNULL = YES;
+				CLANG_ANALYZER_NUMBER_OBJECT_CONVERSION = YES_AGGRESSIVE;
+				CLANG_CXX_LANGUAGE_STANDARD = "gnu++14";
+				CLANG_CXX_LIBRARY = "libc++";
+				CLANG_ENABLE_MODULES = YES;
+				CLANG_ENABLE_OBJC_ARC = YES;
+				CLANG_WARN_BLOCK_CAPTURE_AUTORELEASING = YES;
+				CLANG_WARN_BOOL_CONVERSION = YES;
+				CLANG_WARN_CONSTANT_CONVERSION = YES;
+				CLANG_WARN_DEPRECATED_OBJC_IMPLEMENTATIONS = YES;
+				CLANG_WARN_DIRECT_OBJC_ISA_USAGE = YES_ERROR;
+				CLANG_WARN_DOCUMENTATION_COMMENTS = YES;
+				CLANG_WARN_EMPTY_BODY = YES;
+				CLANG_WARN_ENUM_CONVERSION = YES;
+				CLANG_WARN_INFINITE_RECURSION = YES;
+				CLANG_WARN_INT_CONVERSION = YES;
+				CLANG_WARN_NON_LITERAL_NULL_CONVERSION = YES;
+				CLANG_WARN_OBJC_LITERAL_CONVERSION = YES;
+				CLANG_WARN_OBJC_ROOT_CLASS = YES_ERROR;
+				CLANG_WARN_RANGE_LOOP_ANALYSIS = YES;
+				CLANG_WARN_SUSPICIOUS_MOVE = YES;
+				CODE_SIGN_IDENTITY = "-";
+				COPY_PHASE_STRIP = NO;
+				DEBUG_INFORMATION_FORMAT = "dwarf-with-dsym";
+				ENABLE_NS_ASSERTIONS = NO;
+				ENABLE_STRICT_OBJC_MSGSEND = YES;
+				GCC_C_LANGUAGE_STANDARD = gnu11;
+				GCC_NO_COMMON_BLOCKS = YES;
+				GCC_WARN_64_TO_32_BIT_CONVERSION = YES;
+				GCC_WARN_ABOUT_RETURN_TYPE = YES_ERROR;
+				GCC_WARN_UNINITIALIZED_AUTOS = YES_AGGRESSIVE;
+				GCC_WARN_UNUSED_FUNCTION = YES;
+				GCC_WARN_UNUSED_VARIABLE = YES;
+				MACOSX_DEPLOYMENT_TARGET = 10.11;
+				MTL_ENABLE_DEBUG_INFO = NO;
+				SDKROOT = macosx;
+				SWIFT_COMPILATION_MODE = wholemodule;
+				SWIFT_OPTIMIZATION_LEVEL = "-O";
+			};
+			name = Release;
+		};
+		33CC10FC2044A3C60003C045 /* Debug */ = {
+			isa = XCBuildConfiguration;
+			baseConfigurationReference = 33E5194F232828860026EE4D /* AppInfo.xcconfig */;
+			buildSettings = {
+				ASSETCATALOG_COMPILER_APPICON_NAME = AppIcon;
+				CLANG_ENABLE_MODULES = YES;
+				CODE_SIGN_ENTITLEMENTS = Runner/DebugProfile.entitlements;
+				CODE_SIGN_STYLE = Automatic;
+				COMBINE_HIDPI_IMAGES = YES;
+				FRAMEWORK_SEARCH_PATHS = (
+					"$(inherited)",
+					"$(PROJECT_DIR)/Flutter/ephemeral",
+				);
+				INFOPLIST_FILE = Runner/Info.plist;
+				LD_RUNPATH_SEARCH_PATHS = (
+					"$(inherited)",
+					"@executable_path/../Frameworks",
+				);
+				PROVISIONING_PROFILE_SPECIFIER = "";
+				SWIFT_OPTIMIZATION_LEVEL = "-Onone";
+				SWIFT_VERSION = 5.0;
+			};
+			name = Debug;
+		};
+		33CC10FD2044A3C60003C045 /* Release */ = {
+			isa = XCBuildConfiguration;
+			baseConfigurationReference = 33E5194F232828860026EE4D /* AppInfo.xcconfig */;
+			buildSettings = {
+				ASSETCATALOG_COMPILER_APPICON_NAME = AppIcon;
+				CLANG_ENABLE_MODULES = YES;
+				CODE_SIGN_ENTITLEMENTS = Runner/Release.entitlements;
+				CODE_SIGN_STYLE = Automatic;
+				COMBINE_HIDPI_IMAGES = YES;
+				FRAMEWORK_SEARCH_PATHS = (
+					"$(inherited)",
+					"$(PROJECT_DIR)/Flutter/ephemeral",
+				);
+				INFOPLIST_FILE = Runner/Info.plist;
+				LD_RUNPATH_SEARCH_PATHS = (
+					"$(inherited)",
+					"@executable_path/../Frameworks",
+				);
+				PROVISIONING_PROFILE_SPECIFIER = "";
+				SWIFT_VERSION = 5.0;
+			};
+			name = Release;
+		};
+		33CC111C2044C6BA0003C045 /* Debug */ = {
+			isa = XCBuildConfiguration;
+			buildSettings = {
+				CODE_SIGN_STYLE = Manual;
+				PRODUCT_NAME = "$(TARGET_NAME)";
+			};
+			name = Debug;
+		};
+		33CC111D2044C6BA0003C045 /* Release */ = {
+			isa = XCBuildConfiguration;
+			buildSettings = {
+				CODE_SIGN_STYLE = Automatic;
+				PRODUCT_NAME = "$(TARGET_NAME)";
+			};
+			name = Release;
+		};
+/* End XCBuildConfiguration section */
+
+/* Begin XCConfigurationList section */
+		33CC10E82044A3C60003C045 /* Build configuration list for PBXProject "Runner" */ = {
+			isa = XCConfigurationList;
+			buildConfigurations = (
+				33CC10F92044A3C60003C045 /* Debug */,
+				33CC10FA2044A3C60003C045 /* Release */,
+				338D0CE9231458BD00FA5F75 /* Profile */,
+			);
+			defaultConfigurationIsVisible = 0;
+			defaultConfigurationName = Release;
+		};
+		33CC10FB2044A3C60003C045 /* Build configuration list for PBXNativeTarget "Runner" */ = {
+			isa = XCConfigurationList;
+			buildConfigurations = (
+				33CC10FC2044A3C60003C045 /* Debug */,
+				33CC10FD2044A3C60003C045 /* Release */,
+				338D0CEA231458BD00FA5F75 /* Profile */,
+			);
+			defaultConfigurationIsVisible = 0;
+			defaultConfigurationName = Release;
+		};
+		33CC111B2044C6BA0003C045 /* Build configuration list for PBXAggregateTarget "Flutter Assemble" */ = {
+			isa = XCConfigurationList;
+			buildConfigurations = (
+				33CC111C2044C6BA0003C045 /* Debug */,
+				33CC111D2044C6BA0003C045 /* Release */,
+				338D0CEB231458BD00FA5F75 /* Profile */,
+			);
+			defaultConfigurationIsVisible = 0;
+			defaultConfigurationName = Release;
+		};
+/* End XCConfigurationList section */
+	};
+	rootObject = 33CC10E52044A3C60003C045 /* Project object */;
+}

example/macos/Runner.xcodeproj/project.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist

+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>IDEDidComputeMac32BitWarning</key>
+	<true/>
+</dict>
+</plist>

example/macos/Runner.xcodeproj/xcshareddata/xcschemes/Runner.xcscheme

+<?xml version="1.0" encoding="UTF-8"?>
+<Scheme
+   LastUpgradeVersion = "1000"
+   version = "1.3">
+   <BuildAction
+      parallelizeBuildables = "YES"
+      buildImplicitDependencies = "YES">
+      <BuildActionEntries>
+         <BuildActionEntry
+            buildForTesting = "YES"
+            buildForRunning = "YES"
+            buildForProfiling = "YES"
+            buildForArchiving = "YES"
+            buildForAnalyzing = "YES">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "33CC10EC2044A3C60003C045"
+               BuildableName = "example.app"
+               BlueprintName = "Runner"
+               ReferencedContainer = "container:Runner.xcodeproj">
+            </BuildableReference>
+         </BuildActionEntry>
+      </BuildActionEntries>
+   </BuildAction>
+   <TestAction
+      buildConfiguration = "Debug"
+      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
+      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      shouldUseLaunchSchemeArgsEnv = "YES">
+      <Testables>
+         <TestableReference
+            skipped = "NO">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "00380F9121DF178D00097171"
+               BuildableName = "RunnerUITests.xctest"
+               BlueprintName = "RunnerUITests"
+               ReferencedContainer = "container:Runner.xcodeproj">
+            </BuildableReference>
+         </TestableReference>
+      </Testables>
+      <MacroExpansion>
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "33CC10EC2044A3C60003C045"
+            BuildableName = "example.app"
+            BlueprintName = "Runner"
+            ReferencedContainer = "container:Runner.xcodeproj">
+         </BuildableReference>
+      </MacroExpansion>
+      <AdditionalOptions>
+      </AdditionalOptions>
+   </TestAction>
+   <LaunchAction
+      buildConfiguration = "Debug"
+      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
+      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      launchStyle = "0"
+      useCustomWorkingDirectory = "NO"
+      ignoresPersistentStateOnLaunch = "NO"
+      debugDocumentVersioning = "YES"
+      debugServiceExtension = "internal"
+      allowLocationSimulation = "YES">
+      <BuildableProductRunnable
+         runnableDebuggingMode = "0">
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "33CC10EC2044A3C60003C045"
+            BuildableName = "example.app"
+            BlueprintName = "Runner"
+            ReferencedContainer = "container:Runner.xcodeproj">
+         </BuildableReference>
+      </BuildableProductRunnable>
+      <AdditionalOptions>
+      </AdditionalOptions>
+   </LaunchAction>
+   <ProfileAction
+      buildConfiguration = "Release"
+      shouldUseLaunchSchemeArgsEnv = "YES"
+      savedToolIdentifier = ""
+      useCustomWorkingDirectory = "NO"
+      debugDocumentVersioning = "YES">
+      <BuildableProductRunnable
+         runnableDebuggingMode = "0">
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "33CC10EC2044A3C60003C045"
+            BuildableName = "example.app"
+            BlueprintName = "Runner"
+            ReferencedContainer = "container:Runner.xcodeproj">
+         </BuildableReference>
+      </BuildableProductRunnable>
+   </ProfileAction>
+   <AnalyzeAction
+      buildConfiguration = "Debug">
+   </AnalyzeAction>
+   <ArchiveAction
+      buildConfiguration = "Release"
+      revealArchiveInOrganizer = "YES">
+   </ArchiveAction>
+</Scheme>

example/macos/Runner.xcworkspace/contents.xcworkspacedata

+<?xml version="1.0" encoding="UTF-8"?>
+<Workspace
+   version = "1.0">
+   <FileRef
+      location = "group:Runner.xcodeproj">
+   </FileRef>
+   <FileRef
+      location = "group:Pods/Pods.xcodeproj">
+   </FileRef>
+</Workspace>

example/macos/Runner.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist

+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>IDEDidComputeMac32BitWarning</key>
+	<true/>
+</dict>
+</plist>

example/macos/Runner/AppDelegate.swift

+import Cocoa
+import FlutterMacOS
+
+@NSApplicationMain
+class AppDelegate: FlutterAppDelegate {
+  override func applicationShouldTerminateAfterLastWindowClosed(_ sender: NSApplication) -> Bool {
+    return true
+  }
+}

example/macos/Runner/Assets.xcassets/AppIcon.appiconset/Contents.json

+{
+  "images" : [
+    {
+      "size" : "16x16",
+      "idiom" : "mac",
+      "filename" : "app_icon_16.png",
+      "scale" : "1x"
+    },
+    {
+      "size" : "16x16",
+      "idiom" : "mac",
+      "filename" : "app_icon_32.png",
+      "scale" : "2x"
+    },
+    {
+      "size" : "32x32",
+      "idiom" : "mac",
+      "filename" : "app_icon_32.png",
+      "scale" : "1x"
+    },
+    {
+      "size" : "32x32",
+      "idiom" : "mac",
+      "filename" : "app_icon_64.png",
+      "scale" : "2x"
+    },
+    {
+      "size" : "128x128",
+      "idiom" : "mac",
+      "filename" : "app_icon_128.png",
+      "scale" : "1x"
+    },
+    {
+      "size" : "128x128",
+      "idiom" : "mac",
+      "filename" : "app_icon_256.png",
+      "scale" : "2x"
+    },
+    {
+      "size" : "256x256",
+      "idiom" : "mac",
+      "filename" : "app_icon_256.png",
+      "scale" : "1x"
+    },
+    {
+      "size" : "256x256",
+      "idiom" : "mac",
+      "filename" : "app_icon_512.png",
+      "scale" : "2x"
+    },
+    {
+      "size" : "512x512",
+      "idiom" : "mac",
+      "filename" : "app_icon_512.png",
+      "scale" : "1x"
+    },
+    {
+      "size" : "512x512",
+      "idiom" : "mac",
+      "filename" : "app_icon_1024.png",
+      "scale" : "2x"
+    }
+  ],
+  "info" : {
+    "version" : 1,
+    "author" : "xcode"
+  }
+}

example/macos/Runner/Base.lproj/MainMenu.xib

+<?xml version="1.0" encoding="UTF-8"?>
+<document type="com.apple.InterfaceBuilder3.Cocoa.XIB" version="3.0" toolsVersion="14490.70" targetRuntime="MacOSX.Cocoa" propertyAccessControl="none" useAutolayout="YES" customObjectInstantitationMethod="direct">
+    <dependencies>
+        <deployment identifier="macosx"/>
+        <plugIn identifier="com.apple.InterfaceBuilder.CocoaPlugin" version="14490.70"/>
+        <capability name="documents saved in the Xcode 8 format" minToolsVersion="8.0"/>
+    </dependencies>
+    <objects>
+        <customObject id="-2" userLabel="File's Owner" customClass="NSApplication">
+            <connections>
+                <outlet property="delegate" destination="Voe-Tx-rLC" id="GzC-gU-4Uq"/>
+            </connections>
+        </customObject>
+        <customObject id="-1" userLabel="First Responder" customClass="FirstResponder"/>
+        <customObject id="-3" userLabel="Application" customClass="NSObject"/>
+        <customObject id="Voe-Tx-rLC" customClass="AppDelegate" customModule="Runner" customModuleProvider="target">
+            <connections>
+                <outlet property="applicationMenu" destination="uQy-DD-JDr" id="XBo-yE-nKs"/>
+                <outlet property="mainFlutterWindow" destination="QvC-M9-y7g" id="gIp-Ho-8D9"/>
+            </connections>
+        </customObject>
+        <customObject id="YLy-65-1bz" customClass="NSFontManager"/>
+        <menu title="Main Menu" systemMenu="main" id="AYu-sK-qS6">
+            <items>
+                <menuItem title="APP_NAME" id="1Xt-HY-uBw">
+                    <modifierMask key="keyEquivalentModifierMask"/>
+                    <menu key="submenu" title="APP_NAME" systemMenu="apple" id="uQy-DD-JDr">
+                        <items>
+                            <menuItem title="About APP_NAME" id="5kV-Vb-QxS">
+                                <modifierMask key="keyEquivalentModifierMask"/>
+                                <connections>
+                                    <action selector="orderFrontStandardAboutPanel:" target="-1" id="Exp-CZ-Vem"/>
+                                </connections>
+                            </menuItem>
+                            <menuItem isSeparatorItem="YES" id="VOq-y0-SEH"/>
+                            <menuItem title="Preferences…" keyEquivalent="," id="BOF-NM-1cW"/>
+                            <menuItem isSeparatorItem="YES" id="wFC-TO-SCJ"/>
+                            <menuItem title="Services" id="NMo-om-nkz">
+                                <modifierMask key="keyEquivalentModifierMask"/>
+                                <menu key="submenu" title="Services" systemMenu="services" id="hz9-B4-Xy5"/>
+                            </menuItem>
+                            <menuItem isSeparatorItem="YES" id="4je-JR-u6R"/>
+                            <menuItem title="Hide APP_NAME" keyEquivalent="h" id="Olw-nP-bQN">
+                                <connections>
+                                    <action selector="hide:" target="-1" id="PnN-Uc-m68"/>
+                                </connections>
+                            </menuItem>
+                            <menuItem title="Hide Others" keyEquivalent="h" id="Vdr-fp-XzO">
+                                <modifierMask key="keyEquivalentModifierMask" option="YES" command="YES"/>
+                                <connections>
+                                    <action selector="hideOtherApplications:" target="-1" id="VT4-aY-XCT"/>
+                                </connections>
+                            </menuItem>
+                            <menuItem title="Show All" id="Kd2-mp-pUS">
+                                <modifierMask key="keyEquivalentModifierMask"/>
+                                <connections>
+                                    <action selector="unhideAllApplications:" target="-1" id="Dhg-Le-xox"/>
+                                </connections>
+                            </menuItem>
+                            <menuItem isSeparatorItem="YES" id="kCx-OE-vgT"/>
+                            <menuItem title="Quit APP_NAME" keyEquivalent="q" id="4sb-4s-VLi">
+                                <connections>
+                                    <action selector="terminate:" target="-1" id="Te7-pn-YzF"/>
+                                </connections>
+                            </menuItem>
+                        </items>
+                    </menu>
+                </menuItem>
+                <menuItem title="Edit" id="5QF-Oa-p0T">
+                    <modifierMask key="keyEquivalentModifierMask"/>
+                    <menu key="submenu" title="Edit" id="W48-6f-4Dl">
+                        <items>
+                            <menuItem title="Undo" keyEquivalent="z" id="dRJ-4n-Yzg">
+                                <connections>
+                                    <action selector="undo:" target="-1" id="M6e-cu-g7V"/>
+                                </connections>
+                            </menuItem>
+                            <menuItem title="Redo" keyEquivalent="Z" id="6dh-zS-Vam">
+                                <connections>
+                                    <action selector="redo:" target="-1" id="oIA-Rs-6OD"/>
+                                </connections>
+                            </menuItem>
+                            <menuItem isSeparatorItem="YES" id="WRV-NI-Exz"/>
+                            <menuItem title="Cut" keyEquivalent="x" id="uRl-iY-unG">
+                                <connections>
+                                    <action selector="cut:" target="-1" id="YJe-68-I9s"/>
+                                </connections>
+                            </menuItem>
+                            <menuItem title="Copy" keyEquivalent="c" id="x3v-GG-iWU">
+                                <connections>
+                                    <action selector="copy:" target="-1" id="G1f-GL-Joy"/>
+                                </connections>
+                            </menuItem>
+                            <menuItem title="Paste" keyEquivalent="v" id="gVA-U4-sdL">
+                                <connections>
+                                    <action selector="paste:" target="-1" id="UvS-8e-Qdg"/>
+                                </connections>
+                            </menuItem>
+                            <menuItem title="Paste and Match Style" keyEquivalent="V" id="WeT-3V-zwk">
+                                <modifierMask key="keyEquivalentModifierMask" option="YES" command="YES"/>
+                                <connections>
+                                    <action selector="pasteAsPlainText:" target="-1" id="cEh-KX-wJQ"/>
+                                </connections>
+                            </menuItem>
+                            <menuItem title="Delete" id="pa3-QI-u2k">
+                                <modifierMask key="keyEquivalentModifierMask"/>
+                                <connections>
+                                    <action selector="delete:" target="-1" id="0Mk-Ml-PaM"/>
+                                </connections>
+                            </menuItem>
+                            <menuItem title="Select All" keyEquivalent="a" id="Ruw-6m-B2m">
+                                <connections>
+                                    <action selector="selectAll:" target="-1" id="VNm-Mi-diN"/>
+                                </connections>
+                            </menuItem>
+                            <menuItem isSeparatorItem="YES" id="uyl-h8-XO2"/>
+                            <menuItem title="Find" id="4EN-yA-p0u">
+                                <modifierMask key="keyEquivalentModifierMask"/>
+                                <menu key="submenu" title="Find" id="1b7-l0-nxx">
+                                    <items>
+                                        <menuItem title="Find…" tag="1" keyEquivalent="f" id="Xz5-n4-O0W">
+                                            <connections>
+                                                <action selector="performFindPanelAction:" target="-1" id="cD7-Qs-BN4"/>
+                                            </connections>
+                                        </menuItem>
+                                        <menuItem title="Find and Replace…" tag="12" keyEquivalent="f" id="YEy-JH-Tfz">
+                                            <modifierMask key="keyEquivalentModifierMask" option="YES" command="YES"/>
+                                            <connections>
+                                                <action selector="performFindPanelAction:" target="-1" id="WD3-Gg-5AJ"/>
+                                            </connections>
+                                        </menuItem>
+                                        <menuItem title="Find Next" tag="2" keyEquivalent="g" id="q09-fT-Sye">
+                                            <connections>
+                                                <action selector="performFindPanelAction:" target="-1" id="NDo-RZ-v9R"/>
+                                            </connections>
+                                        </menuItem>
+                                        <menuItem title="Find Previous" tag="3" keyEquivalent="G" id="OwM-mh-QMV">
+                                            <connections>
+                                                <action selector="performFindPanelAction:" target="-1" id="HOh-sY-3ay"/>
+                                            </connections>
+                                        </menuItem>
+                                        <menuItem title="Use Selection for Find" tag="7" keyEquivalent="e" id="buJ-ug-pKt">
+                                            <connections>
+                                                <action selector="performFindPanelAction:" target="-1" id="U76-nv-p5D"/>
+                                            </connections>
+                                        </menuItem>
+                                        <menuItem title="Jump to Selection" keyEquivalent="j" id="S0p-oC-mLd">
+                                            <connections>
+                                                <action selector="centerSelectionInVisibleArea:" target="-1" id="IOG-6D-g5B"/>
+                                            </connections>
+                                        </menuItem>
+                                    </items>
+                                </menu>
+                            </menuItem>
+                            <menuItem title="Spelling and Grammar" id="Dv1-io-Yv7">
+                                <modifierMask key="keyEquivalentModifierMask"/>
+                                <menu key="submenu" title="Spelling" id="3IN-sU-3Bg">
+                                    <items>
+                                        <menuItem title="Show Spelling and Grammar" keyEquivalent=":" id="HFo-cy-zxI">
+                                            <connections>
+                                                <action selector="showGuessPanel:" target="-1" id="vFj-Ks-hy3"/>
+                                            </connections>
+                                        </menuItem>
+                                        <menuItem title="Check Document Now" keyEquivalent=";" id="hz2-CU-CR7">
+                                            <connections>
+                                                <action selector="checkSpelling:" target="-1" id="fz7-VC-reM"/>
+                                            </connections>
+                                        </menuItem>
+                                        <menuItem isSeparatorItem="YES" id="bNw-od-mp5"/>
+                                        <menuItem title="Check Spelling While Typing" id="rbD-Rh-wIN">
+                                            <modifierMask key="keyEquivalentModifierMask"/>
+                                            <connections>
+                                                <action selector="toggleContinuousSpellChecking:" target="-1" id="7w6-Qz-0kB"/>
+                                            </connections>
+                                        </menuItem>
+                                        <menuItem title="Check Grammar With Spelling" id="mK6-2p-4JG">
+                                            <modifierMask key="keyEquivalentModifierMask"/>
+                                            <connections>
+                                                <action selector="toggleGrammarChecking:" target="-1" id="muD-Qn-j4w"/>
+                                            </connections>
+                                        </menuItem>
+                                        <menuItem title="Correct Spelling Automatically" id="78Y-hA-62v">
+                                            <modifierMask key="keyEquivalentModifierMask"/>
+                                            <connections>
+                                                <action selector="toggleAutomaticSpellingCorrection:" target="-1" id="2lM-Qi-WAP"/>
+                                            </connections>
+                                        </menuItem>
+                                    </items>
+                                </menu>
+                            </menuItem>
+                            <menuItem title="Substitutions" id="9ic-FL-obx">
+                                <modifierMask key="keyEquivalentModifierMask"/>
+                                <menu key="submenu" title="Substitutions" id="FeM-D8-WVr">
+                                    <items>
+                                        <menuItem title="Show Substitutions" id="z6F-FW-3nz">
+                                            <modifierMask key="keyEquivalentModifierMask"/>
+                                            <connections>
+                                                <action selector="orderFrontSubstitutionsPanel:" target="-1" id="oku-mr-iSq"/>
+                                            </connections>
+                                        </menuItem>
+                                        <menuItem isSeparatorItem="YES" id="gPx-C9-uUO"/>
+                                        <menuItem title="Smart Copy/Paste" id="9yt-4B-nSM">
+                                            <modifierMask key="keyEquivalentModifierMask"/>
+                                            <connections>
+                                                <action selector="toggleSmartInsertDelete:" target="-1" id="3IJ-Se-DZD"/>
+                                            </connections>
+                                        </menuItem>
+                                        <menuItem title="Smart Quotes" id="hQb-2v-fYv">
+                                            <modifierMask key="keyEquivalentModifierMask"/>
+                                            <connections>
+                                                <action selector="toggleAutomaticQuoteSubstitution:" target="-1" id="ptq-xd-QOA"/>
+                                            </connections>
+                                        </menuItem>
+                                        <menuItem title="Smart Dashes" id="rgM-f4-ycn">
+                                            <modifierMask key="keyEquivalentModifierMask"/>
+                                            <connections>
+                                                <action selector="toggleAutomaticDashSubstitution:" target="-1" id="oCt-pO-9gS"/>
+                                            </connections>
+                                        </menuItem>
+                                        <menuItem title="Smart Links" id="cwL-P1-jid">
+                                            <modifierMask key="keyEquivalentModifierMask"/>
+                                            <connections>
+                                                <action selector="toggleAutomaticLinkDetection:" target="-1" id="Gip-E3-Fov"/>
+                                            </connections>
+                                        </menuItem>
+                                        <menuItem title="Data Detectors" id="tRr-pd-1PS">
+                                            <modifierMask key="keyEquivalentModifierMask"/>
+                                            <connections>
+                                                <action selector="toggleAutomaticDataDetection:" target="-1" id="R1I-Nq-Kbl"/>
+                                            </connections>
+                                        </menuItem>
+                                        <menuItem title="Text Replacement" id="HFQ-gK-NFA">
+                                            <modifierMask key="keyEquivalentModifierMask"/>
+                                            <connections>
+                                                <action selector="toggleAutomaticTextReplacement:" target="-1" id="DvP-Fe-Py6"/>
+                                            </connections>
+                                        </menuItem>
+                                    </items>
+                                </menu>
+                            </menuItem>
+                            <menuItem title="Transformations" id="2oI-Rn-ZJC">
+                                <modifierMask key="keyEquivalentModifierMask"/>
+                                <menu key="submenu" title="Transformations" id="c8a-y6-VQd">
+                                    <items>
+                                        <menuItem title="Make Upper Case" id="vmV-6d-7jI">
+                                            <modifierMask key="keyEquivalentModifierMask"/>
+                                            <connections>
+                                                <action selector="uppercaseWord:" target="-1" id="sPh-Tk-edu"/>
+                                            </connections>
+                                        </menuItem>
+                                        <menuItem title="Make Lower Case" id="d9M-CD-aMd">
+                                            <modifierMask key="keyEquivalentModifierMask"/>
+                                            <connections>
+                                                <action selector="lowercaseWord:" target="-1" id="iUZ-b5-hil"/>
+                                            </connections>
+                                        </menuItem>
+                                        <menuItem title="Capitalize" id="UEZ-Bs-lqG">
+                                            <modifierMask key="keyEquivalentModifierMask"/>
+                                            <connections>
+                                                <action selector="capitalizeWord:" target="-1" id="26H-TL-nsh"/>
+                                            </connections>
+                                        </menuItem>
+                                    </items>
+                                </menu>
+                            </menuItem>
+                            <menuItem title="Speech" id="xrE-MZ-jX0">
+                                <modifierMask key="keyEquivalentModifierMask"/>
+                                <menu key="submenu" title="Speech" id="3rS-ZA-NoH">
+                                    <items>
+                                        <menuItem title="Start Speaking" id="Ynk-f8-cLZ">
+                                            <modifierMask key="keyEquivalentModifierMask"/>
+                                            <connections>
+                                                <action selector="startSpeaking:" target="-1" id="654-Ng-kyl"/>
+                                            </connections>
+                                        </menuItem>
+                                        <menuItem title="Stop Speaking" id="Oyz-dy-DGm">
+                                            <modifierMask key="keyEquivalentModifierMask"/>
+                                            <connections>
+                                                <action selector="stopSpeaking:" target="-1" id="dX8-6p-jy9"/>
+                                            </connections>
+                                        </menuItem>
+                                    </items>
+                                </menu>
+                            </menuItem>
+                        </items>
+                    </menu>
+                </menuItem>
+                <menuItem title="View" id="H8h-7b-M4v">
+                    <modifierMask key="keyEquivalentModifierMask"/>
+                    <menu key="submenu" title="View" id="HyV-fh-RgO">
+                        <items>
+                            <menuItem title="Enter Full Screen" keyEquivalent="f" id="4J7-dP-txa">
+                                <modifierMask key="keyEquivalentModifierMask" control="YES" command="YES"/>
+                                <connections>
+                                    <action selector="toggleFullScreen:" target="-1" id="dU3-MA-1Rq"/>
+                                </connections>
+                            </menuItem>
+                        </items>
+                    </menu>
+                </menuItem>
+                <menuItem title="Window" id="aUF-d1-5bR">
+                    <modifierMask key="keyEquivalentModifierMask"/>
+                    <menu key="submenu" title="Window" systemMenu="window" id="Td7-aD-5lo">
+                        <items>
+                            <menuItem title="Minimize" keyEquivalent="m" id="OY7-WF-poV">
+                                <connections>
+                                    <action selector="performMiniaturize:" target="-1" id="VwT-WD-YPe"/>
+                                </connections>
+                            </menuItem>
+                            <menuItem title="Zoom" id="R4o-n2-Eq4">
+                                <modifierMask key="keyEquivalentModifierMask"/>
+                                <connections>
+                                    <action selector="performZoom:" target="-1" id="DIl-cC-cCs"/>
+                                </connections>
+                            </menuItem>
+                            <menuItem isSeparatorItem="YES" id="eu3-7i-yIM"/>
+                            <menuItem title="Bring All to Front" id="LE2-aR-0XJ">
+                                <modifierMask key="keyEquivalentModifierMask"/>
+                                <connections>
+                                    <action selector="arrangeInFront:" target="-1" id="DRN-fu-gQh"/>
+                                </connections>
+                            </menuItem>
+                        </items>
+                    </menu>
+                </menuItem>
+            </items>
+            <point key="canvasLocation" x="142" y="-258"/>
+        </menu>
+        <window title="APP_NAME" allowsToolTipsWhenApplicationIsInactive="NO" autorecalculatesKeyViewLoop="NO" releasedWhenClosed="NO" animationBehavior="default" id="QvC-M9-y7g" customClass="MainFlutterWindow" customModule="Runner" customModuleProvider="target">
+            <windowStyleMask key="styleMask" titled="YES" closable="YES" miniaturizable="YES" resizable="YES"/>
+            <rect key="contentRect" x="335" y="390" width="800" height="600"/>
+            <rect key="screenRect" x="0.0" y="0.0" width="2560" height="1577"/>
+            <view key="contentView" wantsLayer="YES" id="EiT-Mj-1SZ">
+                <rect key="frame" x="0.0" y="0.0" width="800" height="600"/>
+                <autoresizingMask key="autoresizingMask"/>
+            </view>
+        </window>
+    </objects>
+</document>

example/macos/Runner/Configs/AppInfo.xcconfig

+// Application-level settings for the Runner target.
+//
+// This may be replaced with something auto-generated from metadata (e.g., pubspec.yaml) in the
+// future. If not, the values below would default to using the project name when this becomes a
+// 'flutter create' template.
+
+// The application's name. By default this is also the title of the Flutter window.
+PRODUCT_NAME = example
+
+// The application's bundle identifier
+PRODUCT_BUNDLE_IDENTIFIER = com.zmtzawqlp.example
+
+// The copyright displayed in application information
+PRODUCT_COPYRIGHT = Copyright © 2020 com.zmtzawqlp. All rights reserved.

example/macos/Runner/Configs/Debug.xcconfig

+#include "../../Flutter/Flutter-Debug.xcconfig"
+#include "Warnings.xcconfig"

example/macos/Runner/Configs/Release.xcconfig

+#include "../../Flutter/Flutter-Release.xcconfig"
+#include "Warnings.xcconfig"

example/macos/Runner/Configs/Warnings.xcconfig

+WARNING_CFLAGS = -Wall -Wconditional-uninitialized -Wnullable-to-nonnull-conversion -Wmissing-method-return-type -Woverlength-strings
+GCC_WARN_UNDECLARED_SELECTOR = YES
+CLANG_UNDEFINED_BEHAVIOR_SANITIZER_NULLABILITY = YES
+CLANG_WARN_UNGUARDED_AVAILABILITY = YES_AGGRESSIVE
+CLANG_WARN__DUPLICATE_METHOD_MATCH = YES
+CLANG_WARN_PRAGMA_PACK = YES
+CLANG_WARN_STRICT_PROTOTYPES = YES
+CLANG_WARN_COMMA = YES
+GCC_WARN_STRICT_SELECTOR_MATCH = YES
+CLANG_WARN_OBJC_REPEATED_USE_OF_WEAK = YES
+CLANG_WARN_OBJC_IMPLICIT_RETAIN_SELF = YES
+GCC_WARN_SHADOW = YES
+CLANG_WARN_UNREACHABLE_CODE = YES

example/macos/Runner/DebugProfile.entitlements

+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>com.apple.security.app-sandbox</key>
+	<true/>
+	<key>com.apple.security.cs.allow-jit</key>
+	<true/>
+	<key>com.apple.security.network.client</key>
+	<true/>
+	<key>com.apple.security.network.server</key>
+	<true/>
+</dict>
+</plist>

example/macos/Runner/Info.plist

+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>CFBundleDevelopmentRegion</key>
+	<string>$(DEVELOPMENT_LANGUAGE)</string>
+	<key>CFBundleExecutable</key>
+	<string>$(EXECUTABLE_NAME)</string>
+	<key>CFBundleIconFile</key>
+	<string></string>
+	<key>CFBundleIdentifier</key>
+	<string>$(PRODUCT_BUNDLE_IDENTIFIER)</string>
+	<key>CFBundleInfoDictionaryVersion</key>
+	<string>6.0</string>
+	<key>CFBundleName</key>
+	<string>$(PRODUCT_NAME)</string>
+	<key>CFBundlePackageType</key>
+	<string>APPL</string>
+	<key>CFBundleShortVersionString</key>
+	<string>$(FLUTTER_BUILD_NAME)</string>
+	<key>CFBundleVersion</key>
+	<string>$(FLUTTER_BUILD_NUMBER)</string>
+	<key>LSMinimumSystemVersion</key>
+	<string>$(MACOSX_DEPLOYMENT_TARGET)</string>
+	<key>NSHumanReadableCopyright</key>
+	<string>$(PRODUCT_COPYRIGHT)</string>
+	<key>NSMainNibFile</key>
+	<string>MainMenu</string>
+	<key>NSPrincipalClass</key>
+	<string>NSApplication</string>
+</dict>
+</plist>

example/macos/Runner/MainFlutterWindow.swift

+import Cocoa
+import FlutterMacOS
+
+class MainFlutterWindow: NSWindow {
+  override func awakeFromNib() {
+    let flutterViewController = FlutterViewController.init()
+    let windowFrame = self.frame
+    self.contentViewController = flutterViewController
+    self.setFrame(windowFrame, display: true)
+
+    RegisterGeneratedPlugins(registry: flutterViewController)
+
+    super.awakeFromNib()
+  }
+}

example/macos/Runner/Release.entitlements

+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>com.apple.security.app-sandbox</key>
+	<true/>
+	<key>com.apple.security.network.client</key>
+	<true/>
+	<key>com.apple.security.network.server</key>
+	<true/>
+</dict>
+</plist>

example/pubspec.yaml

+name: example
+description: A new Flutter project.
+
+version: 1.0.0+1
+
+environment:
+  sdk: ">=2.6.0 <3.0.0"
+  flutter: ">=1.22.4"
+dependencies:
+  flutter:
+    sdk: flutter
+  cupertino_icons: ^0.1.2
+  url_launcher: 5.3.0  
+  http_client_helper: any  
+  extended_image: any    
+  pull_to_refresh_notification: any
+  like_button: any
+  extended_sliver: ^1.0.1
+  waterfall_flow:
+    path: ../
+  flutter_sliver_tracker: ^1.0.0
+  
+
+dev_dependencies:
+  flutter_test:
+    sdk: flutter
+  ff_annotation_route: ^4.0.0
+
+# For information on the generic Dart part of this file, see the
+# following page: https://dart.dev/tools/pub/pubspec
+
+# The following section is specific to Flutter.
+flutter:
+  assets:
+
+  # assets start
+
+  # GENERATED CODE - DO NOT MODIFY MANUALLY
+  # **************************************************************************
+  # Auto generated by https://github.com/fluttercandies/assets_generator
+  # **************************************************************************
+
+    - assets/
+
+  # assets end
+
+  # The following line ensures that the Material Icons font is
+  # included with your application, so that you can use the icons in
+  # the material Icons class.
+  uses-material-design: true
+
+  # To add assets to your application, add an assets section, like this:
+  # assets:
+  #  - images/a_dot_burr.jpeg
+  #  - images/a_dot_ham.jpeg
+
+  # An image asset can refer to one or more resolution-specific "variants", see
+  # https://flutter.dev/assets-and-images/#resolution-aware.
+
+  # For details regarding adding assets from package dependencies, see
+  # https://flutter.dev/assets-and-images/#from-packages
+
+  # To add custom fonts to your application, add a fonts section here,
+  # in this "flutter" section. Each entry in this list should have a
+  # "family" key with the font family name, and a "fonts" key with a
+  # list giving the asset and other descriptors for the font. For
+  # example:
+  # fonts:
+  #   - family: Schyler
+  #     fonts:
+  #       - asset: fonts/Schyler-Regular.ttf
+  #       - asset: fonts/Schyler-Italic.ttf
+  #         style: italic
+  #   - family: Trajan Pro
+  #     fonts:
+  #       - asset: fonts/TrajanPro.ttf
+  #       - asset: fonts/TrajanPro_Bold.ttf
+  #         weight: 700
+  #
+  # For details regarding fonts from package dependencies,
+  # see https://flutter.dev/custom-fonts/#from-packages
\ No newline at end of file

example/test/widget_test.dart

+// This is a basic Flutter widget test.
+//
+// To perform an interaction with a widget in your test, use the WidgetTester
+// utility that Flutter provides. For example, you can send tap and scroll
+// gestures. You can also use WidgetTester to find child widgets in the widget
+// tree, read text, and verify that the values of widget properties are correct.
+
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+import 'package:example/main.dart';
+
+void main() {
+  testWidgets('Counter increments smoke test', (WidgetTester tester) async {
+    // Build our app and trigger a frame.
+    await tester.pumpWidget(MyApp());
+
+    // Verify that our counter starts at 0.
+    expect(find.text('0'), findsOneWidget);
+    expect(find.text('1'), findsNothing);
+
+    // Tap the '+' icon and trigger a frame.
+    await tester.tap(find.byIcon(Icons.add));
+    await tester.pump();
+
+    // Verify that our counter has incremented.
+    expect(find.text('0'), findsNothing);
+    expect(find.text('1'), findsOneWidget);
+  });
+}

example/web/index.html

+<!DOCTYPE html>
+<html>
+<head>
+  <meta charset="UTF-8">
+  <meta content="IE=Edge" http-equiv="X-UA-Compatible">
+  <meta name="description" content="A new Flutter project.">
+
+  <!-- iOS meta tags & icons -->
+  <meta name="apple-mobile-web-app-capable" content="yes">
+  <meta name="apple-mobile-web-status-bar-style" content="black">
+  <meta name="apple-mobile-web-app-title" content="example">
+  <link rel="apple-touch-icon" href="/icons/Icon-192.png">
+
+  <title>example</title>
+  <link rel="manifest" href="/manifest.json">
+</head>
+<body>
+  <!-- This script installs service_worker.js to provide PWA functionality to
+       application. For more information, see:
+       https://developers.google.com/web/fundamentals/primers/service-workers -->
+  <script>
+    if ('serviceWorker' in navigator) {
+      window.addEventListener('load', function () {
+        navigator.serviceWorker.register('/flutter_service_worker.js');
+      });
+    }
+  </script>
+  <script src="main.dart.js" type="application/javascript"></script>
+</body>
+</html>

example/web/manifest.json

+{
+    "name": "example",
+    "short_name": "example",
+    "start_url": ".",
+    "display": "minimal-ui",
+    "background_color": "#0175C2",
+    "theme_color": "#0175C2",
+    "description": "A new Flutter project.",
+    "orientation": "portrait-primary",
+    "prefer_related_applications": false,
+    "icons": [
+        {
+            "src": "icons/Icon-192.png",
+            "sizes": "192x192",
+            "type": "image/png"
+        },
+        {
+            "src": "icons/Icon-512.png",
+            "sizes": "512x512",
+            "type": "image/png"
+        }
+    ]
+}

lib/src/extended/extended_list_library.dart

+import 'package:flutter/rendering.dart';
+import 'typedef.dart';
+
+enum LastChildLayoutType {
+  /// as default child
+  none,
+
+  /// follow max child trailing layout offset and layout with full cross-axis extent
+  /// last child as load more item/no more item in [ExtendedGridView] and [WaterfallFlow]
+  /// with full cross axis extend
+  fullCrossAxisExtent,
+
+  /// as foot at trailing and layout with full cross axis extend
+  /// show no more item at trailing when children are not full of viewport
+  /// if children is full of viewport, it's the same as fullCrossAxisExtent
+  foot,
+}
+
+/// A delegate that provides extensions within the [ExtendedGridView],[ExtendedList],[WaterfallFlow].
+class ExtendedListDelegate {
+  const ExtendedListDelegate({
+    this.lastChildLayoutTypeBuilder,
+    this.collectGarbage,
+    this.viewportBuilder,
+    this.closeToTrailing = false,
+  }) : assert(
+          closeToTrailing != null,
+        );
+
+  /// The builder to get layout type of last child
+  /// Notice: it should only for last child
+  final LastChildLayoutTypeBuilder lastChildLayoutTypeBuilder;
+
+  /// Call when collect garbage, return indexes of children which are disposed to collect
+  final CollectGarbage collectGarbage;
+
+  /// The builder to get indexes in viewport
+  final ViewportBuilder viewportBuilder;
+
+  /// when reverse property of List is true, layout is as following.
+  /// it likes chat list, and new session will insert to zero index
+  /// but it's not right when items are not full of viewport.
+  ///
+  ///      trailing
+  /// -----------------
+  /// |               |
+  /// |               |
+  /// |     item2     |
+  /// |     item1     |
+  /// |     item0     |
+  /// -----------------
+  ///      leading
+  ///
+  /// to solve it, you could set closeToTrailing to true, layout is as following.
+  /// support [ExtendedGridView],[ExtendedList],[WaterfallFlow]
+  /// it works not only reverse is true.
+  ///
+  ///      trailing
+  /// -----------------
+  /// |     item2     |
+  /// |     item1     |
+  /// |     item0     |
+  /// |               |
+  /// |               |
+  /// -----------------
+  ///      leading
+  ///
+  final bool closeToTrailing;
+}
+
+/// mixin of extended list render
+/// if sliver is all out of viewport then return [-1,-1] or nothing
+mixin ExtendedRenderObjectMixin on RenderSliverMultiBoxAdaptor {
+  /// call ViewportBuilder if it's not null
+  void callViewportBuilder({
+    ViewportBuilder viewportBuilder,
+    //ExtentList and GridView can't use paintExtentOf
+    PaintExtentOf getPaintExtend,
+    double mainAxisSpacing,
+  }) {
+    if (viewportBuilder == null) {
+      return;
+    }
+    /// it's not go into viewport
+    if (firstChild == null ||
+        //sometime, remainingPaintExtent is not zero though sliver is not go into viewport
+        //maybe this is issue for viewport
+        (constraints.precedingScrollExtent != 0.0 && constraints.remainingPaintExtent == 0)) {
+      return;
+    }
+    int viewportFirstIndex = -1;
+    int viewportLastIndex = -1;
+    mainAxisSpacing ??= 0;
+    RenderBox viewportFirstChild = firstChild;
+    while (true) {
+      final double layoutOffset = childScrollOffset(viewportFirstChild);
+      final double heightOffset = getPaintExtend != null ? getPaintExtend(viewportFirstChild) : paintExtentOf(viewportFirstChild);// 固定120高度
+      final double trailingOffset = layoutOffset + heightOffset;
+      final double _scrollOffset = constraints.scrollOffset;
+      if (_scrollOffset < trailingOffset) {//layoutOffset - (layoutOffset == 0 ? 0 : mainAxisSpacing) <= _scrollOffset && 
+        final double scale = (trailingOffset - _scrollOffset) / heightOffset;
+        viewportFirstIndex = indexOf(viewportFirstChild);
+        if(scale>=0.8){
+          break;
+        }
+      }
+      viewportFirstChild = childAfter(viewportFirstChild);
+      if (viewportFirstChild == null) {
+        break;
+      }
+    }
+    RenderBox viewportLastChild = lastChild;
+    while (true) {
+      final double layoutOffset = childScrollOffset(viewportLastChild);
+      final double heightOffset = getPaintExtend != null ? getPaintExtend(viewportLastChild) : paintExtentOf(viewportLastChild);
+      final double trailingOffset = layoutOffset + heightOffset;
+      if (layoutOffset < constraints.scrollOffset + constraints.remainingPaintExtent && trailingOffset >= constraints.scrollOffset) {
+        final double scale = (constraints.scrollOffset + constraints.remainingPaintExtent - layoutOffset) / heightOffset;
+        viewportLastIndex = indexOf(viewportLastChild);
+        if(scale>=0.8){
+          break;
+        }
+      }
+      viewportLastChild = childBefore(viewportLastChild);
+      if (viewportLastChild == null) {
+        break;
+      }
+    }
+    viewportBuilder(viewportFirstIndex, viewportLastIndex);
+  }
+
+  /// call CollectGarbage if it's not null
+  void callCollectGarbage({
+    CollectGarbage collectGarbage,
+    int leadingGarbage,
+    int trailingGarbage,
+    int firstIndex,
+    int targetLastIndex,
+  }) {
+    if (collectGarbage == null) {
+      return;
+    }
+
+    final List<int> garbages = <int>[];
+    firstIndex ??= indexOf(firstChild);
+    targetLastIndex ??= indexOf(lastChild);
+    for (int i = leadingGarbage; i > 0; i--) {
+      garbages.add(firstIndex - i);
+    }
+    for (int i = 0; i < trailingGarbage; i++) {
+      garbages.add(targetLastIndex + i);
+    }
+    if (garbages.isNotEmpty) {
+      //call collectGarbage
+      collectGarbage.call(garbages);
+    }
+  }
+
+  /// handle closeToTrailing at begin
+  void handleCloseToTrailingBegin(bool closeToTrailing) {
+    _closeToTrailingDistance = null;
+    // if (closeToTrailing) {
+    //   RenderBox child = firstChild;
+    //   SliverMultiBoxAdaptorParentData childParentData =
+    //       child.parentData as SliverMultiBoxAdaptorParentData;
+    //   if (childParentData.index == 0 && childParentData.layoutOffset != 0) {
+    //     final double distance = childParentData.layoutOffset;
+    //     while (child != null) {
+    //       childParentData = child.parentData as SliverMultiBoxAdaptorParentData;
+    //       childParentData.layoutOffset -= distance;
+    //       child = childAfter(child);
+    //     }
+    //   }
+    // }
+  }
+
+  /// handle closeToTrailing at end
+  double handleCloseToTrailingEnd(
+      bool closeToTrailing, double endScrollOffset) {
+    if (closeToTrailing && endScrollOffset < constraints.remainingPaintExtent) {
+      //RenderBox child = firstChild;
+      final double distance =
+          constraints.remainingPaintExtent - endScrollOffset;
+      _closeToTrailingDistance = distance;
+      // while (child != null) {
+      //   final SliverMultiBoxAdaptorParentData childParentData =
+      //       child.parentData as SliverMultiBoxAdaptorParentData;
+      //   childParentData.layoutOffset += distance;
+      //   child = childAfter(child);
+      // }
+      return constraints.remainingPaintExtent;
+    }
+    return endScrollOffset;
+  }
+
+  double _closeToTrailingDistance;
+
+  double get closeToTrailingDistance => _closeToTrailingDistance ?? 0.0;
+
+  bool get closeToTrailing => extendedListDelegate?.closeToTrailing ?? false;
+
+  ExtendedListDelegate get extendedListDelegate;
+
+  @override
+  double childScrollOffset(RenderObject child) {
+    assert(child != null);
+    assert(child.parent == this);
+    final SliverMultiBoxAdaptorParentData childParentData =
+        child.parentData as SliverMultiBoxAdaptorParentData;
+    return childParentData.layoutOffset + closeToTrailingDistance;
+  }
+}

lib/src/extended/typedef.dart

+import 'package:flutter/rendering.dart';
+
+import 'extended_list_library.dart';
+
+/// The builder to get layout type of last child
+/// Notice: it should only for last child
+typedef LastChildLayoutTypeBuilder = LastChildLayoutType Function(int index);
+
+/// Return indexes of children which are disposed to collect
+typedef CollectGarbage = void Function(List<int> garbages);
+
+/// 
+/// 滑动过程中展示的索引
+/// if sliver is all out of viewport then return [-1,-1]
+/// 
+typedef ViewportBuilder = void Function(int firstIndex, int lastIndex);
+
+/// Return paint extent of child
+typedef PaintExtentOf = double Function(RenderBox child);

lib/src/rendering/sliver_waterfall_flow.dart

+import 'dart:math';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/rendering.dart';
+import 'package:waterfall_flow/src/extended/typedef.dart';
+
+import '../../waterfall_flow.dart';
+
+///
+///  create by zmtzawqlp on 2019/11/9
+///
+
+/// Controls the masonry layout of tiles.
+///
+/// Given the current constraints on the grid, a [SliverGridDelegate] computes
+/// the masonry layout for the tiles in the grid. The tiles can be placed as masonry
+/// layout with equally cross-axis sized and spaced. A contiguous sequence of children are
+/// laid out after the shortest one of the previous row/column。
+///
+/// See also:
+///
+///  * [SliverWaterfallFlowDelegateWithFixedCrossAxisCount], which creates a masonry
+///    layout with a fixed number of tiles in the cross axis.
+///  * [SliverWaterfallFlowDelegateWithMaxCrossAxisExtent], which creates a masonry
+///    layout that have a maximum cross-axis extent.
+///  * [GridMasonryView], which uses this delegate to control the layout of its tiles.
+///  * [SliverWaterfallFlow], which uses this delegate to control the layout of its
+///    tiles.
+///  * [RenderSliverWaterfallFlow], which uses this delegate to control the layout of its
+///    tiles.
+abstract class SliverWaterfallFlowDelegate extends ExtendedListDelegate {
+  /// Creates a delegate that makes masonry layout with tiles in
+  /// the cross axis.
+  ///
+  /// All of the arguments must not be null. The `mainAxisSpacing` and
+  /// `crossAxisSpacing` arguments must not be negative.
+  const SliverWaterfallFlowDelegate({
+    this.mainAxisSpacing = 0.0,
+    this.crossAxisSpacing = 0.0,
+    LastChildLayoutTypeBuilder lastChildLayoutTypeBuilder,
+    CollectGarbage collectGarbage,
+    ViewportBuilder viewportBuilder,
+    bool closeToTrailing = false,
+  })  : assert(mainAxisSpacing != null && mainAxisSpacing >= 0),
+        assert(crossAxisSpacing != null && crossAxisSpacing >= 0),
+        super(
+          lastChildLayoutTypeBuilder: lastChildLayoutTypeBuilder,
+          collectGarbage: collectGarbage,
+          viewportBuilder: viewportBuilder,
+          closeToTrailing: closeToTrailing,
+        );
+
+  /// The number of logical pixels between each child along the main axis.
+  final double mainAxisSpacing;
+
+  /// The number of logical pixels between each child along the cross axis.
+  final double crossAxisSpacing;
+
+  /// Return the offset of the child in the non-scrolling axis.
+  double getCrossAxisOffset(SliverConstraints constraints, int crossAxisIndex) {
+    final bool reverseCrossAxis =
+        axisDirectionIsReversed(constraints.crossAxisDirection);
+    final int crossAxisCount = getCrossAxisCount(constraints);
+    final double childUsableCrossAxisExtent =
+        getChildUsableCrossAxisExtent(constraints);
+    final int actualCrossAxisIndex = (reverseCrossAxis && crossAxisCount > 1)
+        ? crossAxisCount - 1 - crossAxisIndex
+        : crossAxisIndex;
+
+    return actualCrossAxisIndex %
+        crossAxisCount *
+        (childUsableCrossAxisExtent + crossAxisSpacing);
+  }
+
+  /// Return usable cross-axis extent of each child.
+  ///
+  /// It doesn't contain [crossAxisSpacing].
+  double getChildUsableCrossAxisExtent(SliverConstraints constraints) {
+    final int crossAxisCount = getCrossAxisCount(constraints);
+    final double usableCrossAxisExtent = max(0.0,
+        constraints.crossAxisExtent - crossAxisSpacing * (crossAxisCount - 1));
+    return usableCrossAxisExtent / crossAxisCount;
+  }
+
+  /// Return [crossAxisCount] by [SliverWaterfallFlowDelegateWithFixedCrossAxisCount]
+  /// and [SliverWaterfallFlowDelegateWithMaxCrossAxisExtent].
+  int getCrossAxisCount(SliverConstraints constraints);
+
+  /// Return true when the children need to be laid out.
+  ///
+  /// This should compare the fields of the current delegate and the given
+  /// `oldDelegate` and return true if the fields are such that the layout would
+  /// be different.
+  bool shouldRelayout(SliverWaterfallFlowDelegate oldDelegate) {
+    return oldDelegate.mainAxisSpacing != mainAxisSpacing ||
+        oldDelegate.crossAxisSpacing != crossAxisSpacing ||
+        oldDelegate.closeToTrailing != closeToTrailing;
+  }
+
+  LastChildLayoutType getLastChildLayoutType(int index) {
+    if (lastChildLayoutTypeBuilder == null) {
+      return LastChildLayoutType.none;
+    }
+
+    return lastChildLayoutTypeBuilder(index) ?? LastChildLayoutType.none;
+  }
+}
+
+/// Creates masonry layouts with a fixed number of tiles in the cross axis.
+///
+/// For example, if the grid is vertical, this delegate will create a layout
+/// with a fixed number of columns. If the grid is horizontal, this delegate
+/// will create a layout with a fixed number of rows.
+///
+/// This delegate creates grids with equally cross-axis sized and spaced tiles.
+///
+/// See also:
+///
+///  * [SliverWaterfallFlowDelegateWithMaxCrossAxisExtent], which creates a masonry
+///    layout that have a maximum cross-axis extent.
+///  * [MasonryGridView], which uses this delegate to control the layout of its tiles.
+///  * [SliverWaterfallFlow], which uses this delegate to control the layout of its
+///    tiles.
+///  * [RenderSliverWaterfallFlow], which uses this delegate to control the layout of its
+///    tiles.
+class SliverWaterfallFlowDelegateWithFixedCrossAxisCount
+    extends SliverWaterfallFlowDelegate {
+  /// Creates a delegate that makes masonry layouts with a fixed number of tiles in
+  /// the cross axis.
+  ///
+  /// All of the arguments must not be null. The `mainAxisSpacing` and
+  /// `crossAxisSpacing` arguments must not be negative.The `crossAxisCount`
+  /// must be greater than zero.
+  const SliverWaterfallFlowDelegateWithFixedCrossAxisCount({
+    @required this.crossAxisCount,
+    double mainAxisSpacing = 0.0,
+    double crossAxisSpacing = 0.0,
+    LastChildLayoutTypeBuilder lastChildLayoutTypeBuilder,
+    CollectGarbage collectGarbage,
+    ViewportBuilder viewportBuilder,
+    bool closeToTrailing = false,
+  })  : assert(crossAxisCount != null && crossAxisCount > 0),
+        super(
+          mainAxisSpacing: mainAxisSpacing,
+          crossAxisSpacing: crossAxisSpacing,
+          lastChildLayoutTypeBuilder: lastChildLayoutTypeBuilder,
+          collectGarbage: collectGarbage,
+          viewportBuilder: viewportBuilder,
+          closeToTrailing: closeToTrailing,
+        );
+
+  /// The number of children in the cross axis.
+  final int crossAxisCount;
+
+  @override
+  int getCrossAxisCount(SliverConstraints constraints) {
+    return crossAxisCount;
+  }
+
+  @override
+  bool shouldRelayout(SliverWaterfallFlowDelegate oldDelegate) {
+    if (oldDelegate.runtimeType != runtimeType) {
+      return true;
+    }
+
+    return oldDelegate is SliverWaterfallFlowDelegateWithFixedCrossAxisCount &&
+        (oldDelegate.crossAxisCount != crossAxisCount ||
+            super.shouldRelayout(oldDelegate));
+  }
+}
+
+/// Creates masonry layouts with tiles that each have a maximum cross-axis extent.
+///
+/// This delegate will select a cross-axis extent for the tiles that is as
+/// large as possible subject to the following conditions:
+///
+///  - The extent evenly divides the cross-axis extent of the grid.
+///  - The extent is at most [maxCrossAxisExtent].
+///
+/// For example, if the grid is vertical, the grid is 500.0 pixels wide, and
+/// [maxCrossAxisExtent] is 150.0, this delegate will create a grid with 4
+/// columns that are 125.0 pixels wide.
+///
+/// This delegate creates grids with equally cross-axis sized and spaced tiles.
+///
+/// See also:
+///
+///  * [SliverWaterfallFlowDelegateWithFixedCrossAxisCount], which creates a masonry
+///    layout with a fixed number of tiles in the cross axis.
+///  * [MasonryGridView], which uses this delegate to control the layout of its tiles.
+///  * [SliverWaterfallFlow], which uses this delegate to control the layout of its
+///    tiles.
+///  * [RenderSliverWaterfallFlow], which uses this delegate to control the layout of its
+///    tiles.
+class SliverWaterfallFlowDelegateWithMaxCrossAxisExtent
+    extends SliverWaterfallFlowDelegate {
+  /// Creates a delegate that makes masonry layouts with tiles that have a maximum
+  /// cross-axis extent.
+  ///
+  /// All of the arguments must not be null. The [maxCrossAxisExtent],
+  /// [mainAxisSpacing], and [crossAxisSpacing] arguments must not be negative.
+  const SliverWaterfallFlowDelegateWithMaxCrossAxisExtent({
+    @required this.maxCrossAxisExtent,
+    double mainAxisSpacing = 0.0,
+    double crossAxisSpacing = 0.0,
+    LastChildLayoutTypeBuilder lastChildLayoutTypeBuilder,
+    CollectGarbage collectGarbage,
+    ViewportBuilder viewportBuilder,
+    bool closeToTrailing = false,
+  })  : assert(maxCrossAxisExtent != null && maxCrossAxisExtent >= 0),
+        super(
+          mainAxisSpacing: mainAxisSpacing,
+          crossAxisSpacing: crossAxisSpacing,
+          lastChildLayoutTypeBuilder: lastChildLayoutTypeBuilder,
+          collectGarbage: collectGarbage,
+          viewportBuilder: viewportBuilder,
+          closeToTrailing: closeToTrailing,
+        );
+
+  /// The maximum extent of tiles in the cross axis.
+  ///
+  /// This delegate will select a cross-axis extent for the tiles that is as
+  /// large as possible subject to the following conditions:
+  ///
+  ///  - The extent evenly divides the cross-axis extent of the grid.
+  ///  - The extent is at most [maxCrossAxisExtent].
+  ///
+  /// For example, if the grid is vertical, the grid is 500.0 pixels wide, and
+  /// [maxCrossAxisExtent] is 150.0, this delegate will create a grid with 4
+  /// columns that are 125.0 pixels wide.
+  final double maxCrossAxisExtent;
+
+  @override
+  int getCrossAxisCount(SliverConstraints constraints) {
+    return (constraints.crossAxisExtent /
+            (maxCrossAxisExtent + crossAxisSpacing))
+        .ceil();
+  }
+
+  @override
+  bool shouldRelayout(SliverWaterfallFlowDelegate oldDelegate) {
+    if (oldDelegate.runtimeType != runtimeType) {
+      return true;
+    }
+
+    return oldDelegate is SliverWaterfallFlowDelegateWithMaxCrossAxisExtent &&
+        (oldDelegate.maxCrossAxisExtent != maxCrossAxisExtent ||
+            super.shouldRelayout(oldDelegate));
+  }
+}
+
+/// Parent data structure used by [RenderSliverWaterfallFlow].
+class SliverWaterfallFlowParentData extends SliverMultiBoxAdaptorParentData {
+  /// The trailing position of the child relative to the zero scroll offset.
+  ///
+  /// The number of pixels from from the zero scroll offset of the parent sliver
+  /// (the line at which its [SliverConstraints.scrollOffset] is zero) to the
+  /// side of the child closest to that offset.
+  ///
+  /// In a typical list, this does not change as the parent is scrolled.
+  double trailingLayoutOffset;
+
+  /// The index of crossAxis.
+  int crossAxisIndex;
+
+  /// The offset of the child in the non-scrolling axis.
+  ///
+  /// If the scroll axis is vertical, this offset is from the left-most edge of
+  /// the parent to the left-most edge of the child. If the scroll axis is
+  /// horizontal, this offset is from the top-most edge of the parent to the
+  /// top-most edge of the child.
+  double crossAxisOffset;
+
+  /// The indexes of the children in the same index of crossAxis.
+  List<int> indexes = <int>[];
+
+  @override
+  String toString() =>
+      'crossAxisIndex=$crossAxisIndex;crossAxisOffset=$crossAxisOffset;trailingLayoutOffset=$trailingLayoutOffset;indexes$indexes; ${super.toString()}';
+}
+
+/// A sliver that places multiple box children with masonry layouts.
+///
+/// [RenderSliverWaterfallFlow] places its children in arbitrary positions determined by
+/// [gridDelegate]. Each child is forced to have the cross-axis size specified by the
+/// [gridDelegate].
+///
+/// See also:
+///
+///  * [RenderSliverList], which places its children in a linear
+///    array.
+///  * [RenderSliverFixedExtentList], which places its children in a linear
+///    array with a fixed extent in the main axis.
+///  * [RenderSliverGrid], which places its children in arbitrary positions.
+class RenderSliverWaterfallFlow extends RenderSliverMultiBoxAdaptor
+    with ExtendedRenderObjectMixin {
+  /// Creates a sliver that contains multiple box children that whose cross-axis size
+  /// is determined by a delegate and position is determined by masonry rule.
+  ///
+  /// The [childManager] and [gridDelegate] arguments must not be null.
+  RenderSliverWaterfallFlow({
+    @required RenderSliverBoxChildManager childManager,
+    @required SliverWaterfallFlowDelegate gridDelegate,
+  })  : assert(gridDelegate != null),
+        _gridDelegate = gridDelegate,
+        super(childManager: childManager);
+
+  /// It stores parent data of the leading and trailing.
+  _CrossAxisChildrenData _previousCrossAxisChildrenData;
+
+  /// The delegate that controls the size and position of the children.
+  SliverWaterfallFlowDelegate get gridDelegate => _gridDelegate;
+  SliverWaterfallFlowDelegate _gridDelegate;
+  set gridDelegate(SliverWaterfallFlowDelegate value) {
+    assert(value != null);
+    if (_gridDelegate == value) {
+      return;
+    }
+    if (value.shouldRelayout(_gridDelegate)) {
+      markNeedsLayout();
+    }
+    _gridDelegate = value;
+  }
+
+  @override
+  ExtendedListDelegate get extendedListDelegate => _gridDelegate;
+
+  @override
+  void setupParentData(RenderObject child) {
+    if (child.parentData is! SliverWaterfallFlowParentData)
+      child.parentData = SliverWaterfallFlowParentData();
+  }
+
+  @override
+  double childCrossAxisPosition(RenderBox child) {
+    final SliverWaterfallFlowParentData childParentData =
+        child.parentData as SliverWaterfallFlowParentData;
+    return childParentData.crossAxisOffset;
+  }
+
+  @override
+  void performLayout() {
+    childManager.didStartLayout();
+    childManager.setDidUnderflow(false);
+
+    _clearIfNeed();
+
+    final _CrossAxisChildrenData crossAxisChildrenData = _CrossAxisChildrenData(
+      gridDelegate: _gridDelegate,
+      constraints: constraints,
+      leadingChildren: _previousCrossAxisChildrenData?.leadingChildren,
+    );
+
+    final BoxConstraints childConstraints = constraints.asBoxConstraints(
+        crossAxisExtent:
+            _gridDelegate.getChildUsableCrossAxisExtent(constraints));
+
+    final double scrollOffset =
+        constraints.scrollOffset + constraints.cacheOrigin;
+    assert(scrollOffset >= 0.0);
+    final double remainingExtent = constraints.remainingCacheExtent;
+    assert(remainingExtent >= 0.0);
+    final double targetEndScrollOffset = scrollOffset + remainingExtent;
+
+    int leadingGarbage = 0;
+    int trailingGarbage = 0;
+    bool reachedEnd = false;
+
+    // This algorithm in principle is straight-forward: find the leading children
+    // that overlaps the given scrollOffset base on [_previousCrossAxisChildrenData],
+    // creating more children after the shortest one of the previous row/column,
+    // then walk down the list updating and laying out
+    // each child and adding more at the end if necessary until we have enough
+    // children to cover the entire viewport.
+    //
+    // It is complicated by one minor issue, which is that any time you update
+    // or create a child, it's possible that the some of the children that
+    // haven't yet been laid out will be removed, leaving the list in an
+    // inconsistent state, and requiring that missing nodes be recreated.
+    //
+    // To keep this mess tractable, this algorithm starts from what is currently
+    // the first child, if any, and then walks up and/or down from there, so
+    // that the nodes that might get removed are always at the edges of what has
+    // already been laid out.
+
+    // Make sure we have at least one child to start from.
+    if (firstChild == null) {
+      if (!addInitialChild()) {
+        // There are no children.
+        geometry = SliverGeometry.zero;
+        _previousCrossAxisChildrenData = null;
+        childManager.didFinishLayout();
+        return;
+      }
+    }
+
+    // zmt
+    handleCloseToTrailingBegin(_gridDelegate?.closeToTrailing ?? false);
+    // In case,the itemCount is changed, clear all,
+    final SliverWaterfallFlowParentData firstChildParentData =
+        firstChild.parentData as SliverWaterfallFlowParentData;
+    // In case of the itemCount is changed, clear all leading children,
+    // avoid calculate with dirty leading children.
+    if (firstChildParentData.index == 0) {
+      crossAxisChildrenData.clear();
+    }
+
+    // We have at least one child.
+
+    // These variables track the range of children that we have laid out. Within
+    // this range, the children have consecutive indices. Outside this range,
+    // it's possible for a child to get removed without notice.
+    RenderBox leadingChildWithLayout, trailingChildWithLayout;
+
+    // Find the last child that is at or before the scrollOffset.
+    RenderBox earliestUsefulChild = firstChild;
+
+    // A firstChild with null layout offset is likely a result of children
+    // reordering.
+    //
+    // We rely on firstChild to have accurate layout offset. In the case of null
+    // layout offset, we have to find the first child that has valid layout
+    // offset.
+    if (childScrollOffset(firstChild) == null) {
+      int leadingChildrenWithoutLayoutOffset = 0;
+      while (childScrollOffset(earliestUsefulChild) == null) {
+        earliestUsefulChild = childAfter(firstChild);
+        leadingChildrenWithoutLayoutOffset += 1;
+      }
+      // We should be able to destroy children with null layout offset safely,
+      // because they are likely outside of viewport
+      collectGarbage(leadingChildrenWithoutLayoutOffset, 0);
+      assert(firstChild != null);
+    }
+
+    // Find the last child that is at or before the scrollOffset.
+    earliestUsefulChild = firstChild;
+
+    if (crossAxisChildrenData.maxLeadingLayoutOffset > scrollOffset) {
+      RenderBox child = firstChild;
+      // Add children from min index to max index of leading to
+      // make sure indexes are continuous.
+      final int maxLeadingIndex = crossAxisChildrenData.maxLeadingIndex;
+      while (child != null && maxLeadingIndex > indexOf(child)) {
+        child = childAfter(child);
+      }
+      final int minLeadingIndex = crossAxisChildrenData.minLeadingIndex;
+      while (child != null && minLeadingIndex < indexOf(child)) {
+        crossAxisChildrenData.insertLeading(
+            child: child, paintExtentOf: paintExtentOf);
+        child = childBefore(child);
+      }
+
+      while (crossAxisChildrenData.maxLeadingLayoutOffset > scrollOffset) {
+        // We have to add children before the earliestUsefulChild.
+        earliestUsefulChild =
+            insertAndLayoutLeadingChild(childConstraints, parentUsesSize: true);
+
+        if (earliestUsefulChild == null) {
+          final SliverWaterfallFlowParentData data =
+              firstChild.parentData as SliverWaterfallFlowParentData;
+          assert(data.index == 0);
+          // In case of some child is changed small and we ran out of children
+          // before reaching the scroll offset.
+          // We must clear data, avoid calculate with dirty leading children.
+          firstChild.layout(childConstraints, parentUsesSize: true);
+          earliestUsefulChild = firstChild;
+          leadingChildWithLayout = earliestUsefulChild;
+          trailingChildWithLayout ??= earliestUsefulChild;
+          crossAxisChildrenData.clear();
+          break;
+        }
+
+        crossAxisChildrenData.insertLeading(
+            child: earliestUsefulChild, paintExtentOf: paintExtentOf);
+
+        final SliverWaterfallFlowParentData data =
+            earliestUsefulChild.parentData as SliverWaterfallFlowParentData;
+        // item after leadings
+        if (data.layoutOffset == null) {
+          continue;
+        }
+        // firstChildScrollOffset may contain double precision error
+        if (data.layoutOffset < -precisionErrorTolerance) {
+          // The first child doesn't fit within the viewport (underflow) and
+          // there may be additional children above it. Find the real first child
+          // and then correct the scroll position so that there's room for all and
+          // so that the trailing edge of the original firstChild appears where it
+          // was before the scroll offset correction.
+          // do this work incrementally, instead of all at once,
+          // find first child and clear all,
+          // avoid calculate with dirty leading children.
+          while (earliestUsefulChild != null) {
+            assert(firstChild == earliestUsefulChild);
+            earliestUsefulChild = insertAndLayoutLeadingChild(childConstraints,
+                parentUsesSize: true);
+          }
+          final SliverWaterfallFlowParentData data =
+              firstChild.parentData as SliverWaterfallFlowParentData;
+          assert(data.index == 0);
+          crossAxisChildrenData.clear();
+          earliestUsefulChild = firstChild;
+        }
+
+        assert(earliestUsefulChild == firstChild);
+        leadingChildWithLayout = earliestUsefulChild;
+        trailingChildWithLayout ??= earliestUsefulChild;
+      }
+    }
+
+    // At this point, earliestUsefulChild is the first child, and is a child
+    // whose scrollOffset is at or before the scrollOffset, and
+    // leadingChildWithLayout and trailingChildWithLayout are either null or
+    // cover a range of render boxes that we have laid out with the first being
+    // the same as earliestUsefulChild and the last being either at or after the
+    // scroll offset.
+    assert(earliestUsefulChild == firstChild);
+
+    // Make sure we've laid out at least one child.
+    if (leadingChildWithLayout == null) {
+      earliestUsefulChild.layout(
+          _gridDelegate.getLastChildLayoutType(indexOf(earliestUsefulChild)) !=
+                  LastChildLayoutType.none
+              ? constraints.asBoxConstraints()
+              : childConstraints,
+          parentUsesSize: true);
+      leadingChildWithLayout = earliestUsefulChild;
+      trailingChildWithLayout = earliestUsefulChild;
+    }
+
+    // Here, earliestUsefulChild is still the first child, it's got a
+    // scrollOffset that is at or before our actual scrollOffset, and it has
+    // been laid out, and is in fact our leadingChildWithLayout. It's possible
+    // that some children beyond that one have also been laid out.
+
+    bool inLayoutRange = true;
+    RenderBox child = earliestUsefulChild;
+    int index = indexOf(child);
+    crossAxisChildrenData.insert(
+      child: child,
+      childTrailingLayoutOffset: childTrailingLayoutOffset,
+      paintExtentOf: paintExtentOf,
+    );
+
+    bool advance() {
+      // returns true if we advanced, false if we have no more children
+      // This function is used in two different places below, to avoid code duplication.
+      assert(child != null);
+      if (child == trailingChildWithLayout) {
+        inLayoutRange = false;
+      }
+      child = childAfter(child);
+      if (child == null) {
+        inLayoutRange = false;
+      }
+      index += 1;
+      final LastChildLayoutType lastChildLayoutType =
+          _gridDelegate.getLastChildLayoutType(index);
+      final BoxConstraints currentConstraints =
+          lastChildLayoutType != LastChildLayoutType.none
+              ? constraints.asBoxConstraints()
+              : childConstraints;
+
+      if (!inLayoutRange) {
+        if (child == null || indexOf(child) != index) {
+          // We are missing a child. Insert it (and lay it out) if possible.
+
+          child = insertAndLayoutChild(
+            currentConstraints,
+            after: trailingChildWithLayout,
+            parentUsesSize: true,
+          );
+          if (child == null) {
+            // We have run out of children.
+            return false;
+          }
+        } else {
+          // Lay out the child.
+          child.layout(currentConstraints, parentUsesSize: true);
+        }
+        trailingChildWithLayout = child;
+      }
+      assert(child != null);
+      //zmt
+      final SliverWaterfallFlowParentData childParentData =
+          child.parentData as SliverWaterfallFlowParentData;
+      //zmt
+
+      crossAxisChildrenData.insert(
+        child: child,
+        childTrailingLayoutOffset: childTrailingLayoutOffset,
+        paintExtentOf: paintExtentOf,
+      );
+
+      assert(childParentData.index == index);
+      return true;
+    }
+
+    final List<int> leadingGarbages = <int>[];
+
+    // Find the first child that ends after the scroll offset.
+    while (childTrailingLayoutOffset(child) < scrollOffset) {
+      leadingGarbage += 1;
+      leadingGarbages.add(index);
+      if (!advance()) {
+        assert(leadingGarbage == childCount);
+        assert(child == null);
+        // We ran out of children before reaching the scroll offset.
+        // We must inform our parent that this sliver cannot fulfill
+        // its contract and that we need a max scroll offset correction.
+
+        // we want to make sure we keep the trailingChildren around so we know the end scroll offset
+        // if _previousCrossAxisChildrenData is null, we should re-calculate it from index 0.
+        if (_previousCrossAxisChildrenData != null) {
+          final int minTrailingIndex =
+              _previousCrossAxisChildrenData.minTrailingIndex;
+          for (final int index in leadingGarbages) {
+            if (index >= minTrailingIndex) {
+              leadingGarbage -= 1;
+            }
+          }
+        }
+
+        collectGarbage(leadingGarbage, 0);
+
+        final double extent =
+            crossAxisChildrenData.maxChildTrailingLayoutOffset;
+
+        geometry = SliverGeometry(
+          scrollExtent: extent,
+          paintExtent: 0.0,
+          maxPaintExtent: extent,
+        );
+        //_previousCrossAxisChildrenData = null;
+        return;
+      }
+    }
+
+    if (leadingGarbage > 0) {
+      // Make sure the leadings are after the scroll offset
+      while (
+          crossAxisChildrenData.minChildTrailingLayoutOffset < scrollOffset) {
+        if (!advance()) {
+          final int minTrailingIndex = crossAxisChildrenData.minTrailingIndex;
+          // The indexes are continuous, make sure they are less than minTrailingIndex.
+          for (final int index in leadingGarbages) {
+            if (index >= minTrailingIndex) {
+              leadingGarbage--;
+            }
+          }
+          leadingGarbage = max(0, leadingGarbage);
+          break;
+        }
+      }
+      crossAxisChildrenData.setLeading();
+    }
+
+    if (child != null) {
+      final int crossAxisCount = _gridDelegate.getCrossAxisCount(constraints);
+      while (
+          // Now find the first child that ends after our end.
+          crossAxisChildrenData.minChildTrailingLayoutOffset <
+                  targetEndScrollOffset
+              // Make sure leading children are all laid out.
+              ||
+              crossAxisChildrenData.leadingChildren.length < crossAxisCount ||
+              crossAxisChildrenData.leadingChildren.length > childCount ||
+              (child.parentData as SliverWaterfallFlowParentData).index <
+                  crossAxisCount - 1) {
+        if (!advance()) {
+          reachedEnd = true;
+          break;
+        }
+      }
+    }
+
+    // Finally count up all the remaining children and label them as garbage.
+    if (child != null) {
+      child = childAfter(child);
+      while (child != null) {
+        trailingGarbage += 1;
+        child = childAfter(child);
+      }
+    }
+
+    // At this point everything should be good to go, we just have to clean up
+    // the garbage and report the geometry.
+    collectGarbage(leadingGarbage, trailingGarbage);
+    //zmt
+    callCollectGarbage(
+      collectGarbage: _gridDelegate?.collectGarbage,
+      leadingGarbage: leadingGarbage,
+      trailingGarbage: trailingGarbage,
+    );
+
+    assert(debugAssertChildListIsNonEmptyAndContiguous());
+    double estimatedMaxScrollOffset;
+    //zmt
+    double endScrollOffset =
+        _gridDelegate.getLastChildLayoutType(indexOf(lastChild)) ==
+                LastChildLayoutType.none
+            ? crossAxisChildrenData.maxChildTrailingLayoutOffset
+            : childTrailingLayoutOffset(lastChild);
+
+    if (reachedEnd) {
+      estimatedMaxScrollOffset = endScrollOffset;
+    } else {
+      estimatedMaxScrollOffset = childManager.estimateMaxScrollOffset(
+        constraints,
+        firstIndex: indexOf(firstChild),
+        lastIndex: indexOf(lastChild),
+        leadingScrollOffset: childScrollOffset(firstChild),
+        trailingScrollOffset: endScrollOffset,
+      );
+      //zmt
+      assert(estimatedMaxScrollOffset >=
+          endScrollOffset - childScrollOffset(firstChild));
+    }
+
+    ///zmt
+    final double result =
+        handleCloseToTrailingEnd(closeToTrailing, endScrollOffset);
+    if (result != endScrollOffset) {
+      endScrollOffset = result;
+      estimatedMaxScrollOffset = result;
+    }
+
+    final double paintExtent = calculatePaintOffset(
+      constraints,
+      from: childScrollOffset(firstChild),
+      to: endScrollOffset,
+    );
+    final double cacheExtent = calculateCacheOffset(
+      constraints,
+      from: childScrollOffset(firstChild),
+      to: endScrollOffset,
+    );
+    final double targetEndScrollOffsetForPaint =
+        constraints.scrollOffset + constraints.remainingPaintExtent;
+    //zmt
+    callViewportBuilder(viewportBuilder: _gridDelegate?.viewportBuilder);
+
+    geometry = SliverGeometry(
+      scrollExtent: estimatedMaxScrollOffset,
+      paintExtent: paintExtent,
+      cacheExtent: cacheExtent,
+      maxPaintExtent: estimatedMaxScrollOffset,
+      // Conservative to avoid flickering away the clip during scroll.
+      hasVisualOverflow: endScrollOffset > targetEndScrollOffsetForPaint ||
+          constraints.scrollOffset > 0.0,
+    );
+
+    // We may have started the layout while scrolled to the end, which would not
+    // expose a new child.
+    if (estimatedMaxScrollOffset == endScrollOffset) {
+      childManager.setDidUnderflow(true);
+    }
+    childManager.didFinishLayout();
+
+    // Save, for next layout.
+    _previousCrossAxisChildrenData = crossAxisChildrenData;
+  }
+
+  /// Masonry layout maybe have changed. We need to recalculate from the zero index so that
+  /// layouts will not change suddenly when scroll.
+  void _clearIfNeed() {
+    if (_previousCrossAxisChildrenData != null) {
+      if (_previousCrossAxisChildrenData.crossAxisCount !=
+              gridDelegate.getCrossAxisCount(constraints) ||
+          _previousCrossAxisChildrenData.gridDelegate.mainAxisSpacing !=
+              gridDelegate.mainAxisSpacing ||
+          _previousCrossAxisChildrenData.constraints.crossAxisExtent !=
+              constraints.crossAxisExtent) {
+        _previousCrossAxisChildrenData = null;
+        collectGarbage(childCount, 0);
+      }
+    }
+  }
+
+  /// Return the trailing position of the child.
+  double childTrailingLayoutOffset(RenderBox child) {
+    return childScrollOffset(child) + paintExtentOf(child);
+  }
+}
+
+/// Data structure used to calculate masonry layout by [RenderSliverMasonryGrid]
+class _CrossAxisChildrenData {
+  _CrossAxisChildrenData({
+    @required this.gridDelegate,
+    @required this.constraints,
+    List<SliverWaterfallFlowParentData> leadingChildren,
+  })  : leadingChildren =
+            leadingChildren?.toList() ?? <SliverWaterfallFlowParentData>[],
+        trailingChildren =
+            leadingChildren?.toList() ?? <SliverWaterfallFlowParentData>[];
+
+  /// The parent data of leading children.
+  final List<SliverWaterfallFlowParentData> leadingChildren;
+
+  /// The parent data of trailing children.
+  final List<SliverWaterfallFlowParentData> trailingChildren;
+
+  /// A delegate that controls the masonry layout of the children within the [MasonryGridView].
+  final SliverWaterfallFlowDelegate gridDelegate;
+
+  /// Immutable layout constraints for [RenderSliverMasonryGrid] layout.
+  final SliverConstraints constraints;
+
+  /// The number of children in the cross axis.
+  int get crossAxisCount => gridDelegate.getCrossAxisCount(constraints);
+
+  /// Fill the leading at the beginning then the children are
+  /// laid out after the shortest one.
+  void insert({
+    @required RenderBox child,
+    @required double Function(RenderBox child) childTrailingLayoutOffset,
+    @required double Function(RenderBox child) paintExtentOf,
+  }) {
+    final SliverWaterfallFlowParentData data =
+        child.parentData as SliverWaterfallFlowParentData;
+    final LastChildLayoutType lastChildLayoutType =
+        gridDelegate.getLastChildLayoutType(data.index);
+
+    switch (lastChildLayoutType) {
+      case LastChildLayoutType.fullCrossAxisExtent:
+      case LastChildLayoutType.foot:
+        data.crossAxisOffset = 0.0;
+        data.crossAxisIndex = 0;
+        final double size = paintExtentOf(child);
+        if (lastChildLayoutType == LastChildLayoutType.fullCrossAxisExtent ||
+            maxChildTrailingLayoutOffset + size >
+                constraints.remainingPaintExtent ||
+            gridDelegate.closeToTrailing) {
+          data.layoutOffset = maxChildTrailingLayoutOffset;
+        } else {
+          data.layoutOffset = constraints.remainingPaintExtent - size;
+        }
+        data.trailingLayoutOffset = childTrailingLayoutOffset(child);
+        return;
+      case LastChildLayoutType.none:
+        break;
+    }
+
+    if (!leadingChildren.contains(data)) {
+      if (leadingChildren.length != crossAxisCount) {
+        data.crossAxisIndex ??= leadingChildren.length;
+
+        data.crossAxisOffset =
+            gridDelegate.getCrossAxisOffset(constraints, data.crossAxisIndex);
+
+        data.layoutOffset = 0.0;
+        data.indexes.clear();
+        trailingChildren.add(data);
+        leadingChildren.add(data);
+      }
+      // The child after the leading should be put into the trailing.
+      else {
+        if (data.crossAxisIndex != null) {
+          final SliverWaterfallFlowParentData item =
+              trailingChildren.firstWhere(
+            (SliverWaterfallFlowParentData x) =>
+                x.index > data.index && x.crossAxisIndex == data.crossAxisIndex,
+            orElse: () => null,
+          );
+
+          // It is out of the viewport.
+          // It happens when one child has large size in the main axis,
+          if (item != null) {
+            data.trailingLayoutOffset = childTrailingLayoutOffset(child);
+            return;
+          }
+        }
+        // Find the shortest one and laid out after it.
+        final SliverWaterfallFlowParentData min = trailingChildren.reduce(
+          (SliverWaterfallFlowParentData current,
+                  SliverWaterfallFlowParentData next) =>
+              current.trailingLayoutOffset < next.trailingLayoutOffset ||
+                      (current.trailingLayoutOffset ==
+                              next.trailingLayoutOffset &&
+                          current.crossAxisIndex < next.crossAxisIndex)
+                  ? current
+                  : next,
+        );
+
+        data.layoutOffset =
+            min.trailingLayoutOffset + gridDelegate.mainAxisSpacing;
+        data.crossAxisIndex = min.crossAxisIndex;
+        data.crossAxisOffset =
+            gridDelegate.getCrossAxisOffset(constraints, data.crossAxisIndex);
+
+        for (final SliverWaterfallFlowParentData parentData
+            in trailingChildren) {
+          parentData.indexes.remove(min.index);
+        }
+
+        min.indexes.add(min.index);
+        data.indexes = min.indexes;
+
+        trailingChildren.remove(min);
+        trailingChildren.add(data);
+      }
+    }
+
+    data.crossAxisOffset =
+        gridDelegate.getCrossAxisOffset(constraints, data.crossAxisIndex);
+    data.trailingLayoutOffset = childTrailingLayoutOffset(child);
+  }
+
+  /// When maxLeadingLayoutOffset is less than scrollOffset,
+  /// we have to insert child before the scrollOffset base on the leadings.
+  void insertLeading({
+    @required RenderBox child,
+    @required double Function(RenderBox child) paintExtentOf,
+  }) {
+    final SliverWaterfallFlowParentData data =
+        child.parentData as SliverWaterfallFlowParentData;
+    if (!leadingChildren.contains(data)) {
+      final SliverWaterfallFlowParentData leading = leadingChildren.firstWhere(
+        (SliverWaterfallFlowParentData x) => x.indexes.contains(data.index),
+        orElse: () => null,
+      );
+
+      // This child is after the leadings.
+      if (leading == null || data.index > leading.index) {
+        return;
+      }
+
+      // Laid out the child before the leading.
+      data.trailingLayoutOffset =
+          leading.layoutOffset - gridDelegate.mainAxisSpacing;
+      data.layoutOffset = data.trailingLayoutOffset - paintExtentOf(child);
+      data.crossAxisIndex = leading.crossAxisIndex;
+      data.crossAxisOffset =
+          gridDelegate.getCrossAxisOffset(constraints, data.crossAxisIndex);
+      data.indexes = leading.indexes;
+
+      leadingChildren.remove(leading);
+      trailingChildren.remove(leading);
+      leadingChildren.add(data);
+      trailingChildren.add(data);
+    }
+  }
+
+  double get maxLeadingLayoutOffset {
+    if (leadingChildren.isEmpty) {
+      return 0.0;
+    }
+
+    return leadingChildren
+        .reduce((SliverWaterfallFlowParentData current,
+                SliverWaterfallFlowParentData next) =>
+            current.layoutOffset >= next.layoutOffset ? current : next)
+        .layoutOffset;
+  }
+
+  double get minChildTrailingLayoutOffset {
+    if (trailingChildren.isEmpty) {
+      return 0.0;
+    }
+
+    return trailingChildren
+        .reduce((SliverWaterfallFlowParentData current,
+                SliverWaterfallFlowParentData next) =>
+            current.trailingLayoutOffset <= next.trailingLayoutOffset
+                ? current
+                : next)
+        .trailingLayoutOffset;
+  }
+
+  double get maxChildTrailingLayoutOffset {
+    if (trailingChildren.isEmpty) {
+      return 0.0;
+    }
+
+    return trailingChildren
+        .reduce((SliverWaterfallFlowParentData current,
+                SliverWaterfallFlowParentData next) =>
+            current.trailingLayoutOffset >= next.trailingLayoutOffset
+                ? current
+                : next)
+        .trailingLayoutOffset;
+  }
+
+  int get minLeadingIndex {
+    if (leadingChildren.isEmpty) {
+      return -1;
+    }
+
+    return leadingChildren
+        .reduce((SliverWaterfallFlowParentData current,
+                SliverWaterfallFlowParentData next) =>
+            current.index < next.index ? current : next)
+        .index;
+  }
+
+  int get maxLeadingIndex {
+    if (leadingChildren.isEmpty) {
+      return -1;
+    }
+
+    return leadingChildren
+        .reduce((SliverWaterfallFlowParentData current,
+                SliverWaterfallFlowParentData next) =>
+            current.index > next.index ? current : next)
+        .index;
+  }
+
+  int get minTrailingIndex {
+    if (trailingChildren.isEmpty) {
+      return -1;
+    }
+
+    return trailingChildren
+        .reduce((SliverWaterfallFlowParentData current,
+                SliverWaterfallFlowParentData next) =>
+            current.index < next.index ? current : next)
+        .index;
+  }
+
+  void clear() {
+    leadingChildren.clear();
+    trailingChildren.clear();
+  }
+
+  /// Called after all of the leading are after the scroll offset
+  /// That is the final leading.
+  void setLeading() {
+    leadingChildren.clear();
+    leadingChildren.addAll(trailingChildren);
+  }
+}

lib/src/widgets/scroll_view.dart

+import 'package:flutter/gestures.dart';
+import 'package:flutter/widgets.dart' hide ViewportBuilder;
+import 'package:waterfall_flow/src/extended/typedef.dart';
+import 'package:waterfall_flow/src/rendering/sliver_waterfall_flow.dart';
+import 'sliver.dart';
+
+///
+///  create by zmtzawqlp on 2019/11/9
+///
+
+/// A scrollable, 2D array of widgets whose size is variable in the main axis.
+///
+/// The main axis direction of a grid is the direction in which it scrolls (the
+/// [scrollDirection]).
+///
+/// The most commonly used waterfall layouts are [WaterfallFlow.count], which creates a
+/// layout with a fixed number of tiles in the cross axis.
+///
+/// To create a grid with a large (or infinite) number of children, use the
+/// [WaterfallFlow.builder] constructor with a [SliverWaterfallFlowDelegate]
+/// for the [gridDelegate].
+///
+/// To use a custom [SliverWaterfallFlowDelegate], use [WaterfallFlow.custom].
+///
+/// To create a linear array of children, use a [ListView].
+///
+/// To control the initial scroll offset of the scroll view, provide a
+/// [controller] with its [ScrollController.initialScrollOffset] property set.
+///
+/// ## Transitioning to [CustomScrollView]
+///
+/// A [WaterfallFlow] is basically a [CustomScrollView] with a single [SliverWaterfallFlow] in
+/// its [CustomScrollView.slivers] property.
+///
+/// If [WaterfallFlow] is no longer sufficient, for example because the scroll view
+/// is to have both a grid and a list, or because the grid is to be combined
+/// with a [SliverAppBar], etc, it is straight-forward to port code from using
+/// [WaterfallFlow] to using [CustomScrollView] directly.
+///
+/// The [key], [scrollDirection], [reverse], [controller], [primary], [physics],
+/// and [shrinkWrap] properties on [WaterfallFlow] map directly to the identically
+/// named properties on [CustomScrollView].
+///
+/// The [CustomScrollView.slivers] property should be a list containing just a
+/// [SliverWaterfallFlow].
+///
+/// The [childrenDelegate] property on [WaterfallFlow] corresponds to the
+/// [SliverWaterfallFlow.gridDelegate] property, and the [gridDelegate] property on the
+/// [WaterfallFlow] corresponds to the [SliverWaterfallFlow.gridDelegate] property.
+///
+/// The [WaterfallFlow] and [WaterfallFlow.count] constructors' `children` arguments
+/// correspond to the [childrenDelegate] being a [SliverChildListDelegate]
+/// with that same argument.
+/// The [WaterfallFlow.builder] constructor's `itemBuilder` and `childCount` arguments
+/// correspond to the [childrenDelegate] being a [SliverChildBuilderDelegate]
+/// with the matching arguments.
+///
+/// The [WaterfallFlow.count] constructors create custom grid delegates,
+/// and have equivalently named constructor on [SliverWaterfallFlow] to
+/// ease the transition: [SliverWaterfallFlow.count] respectively.
+///
+/// The [padding] property corresponds to having a [SliverPadding] in the
+/// [CustomScrollView.slivers] property instead of the grid itself, and having
+/// the [SliverWaterfallFlow] instead be a child of the [SliverPadding].
+///
+/// By default, [ListView] will automatically pad the list's scrollable
+/// extremities to avoid partial obstructions indicated by [MediaQuery]'s
+/// padding. To avoid this behavior, override with a zero [padding] property.
+///
+/// Once code has been ported to use [CustomScrollView], other slivers, such as
+/// [SliverList] or [SliverAppBar], can be put in the [CustomScrollView.slivers]
+/// list.
+///
+/// {@tool snippet}
+/// This example demonstrates how to create a [WaterfallFlow] with two columns. The
+/// children are spaced apart using the [crossAxisSpacing] and [mainAxisSpacing]
+/// properties.
+///
+/// ![The WaterfallFlow displays six children with different background colors and heights arranged in two columns](https://flutter.github.io/assets-for-api-docs/assets/widgets/grid_view.png)
+///
+/// ```dart
+/// WaterfallFlow.count(
+///   primary: false,
+///   padding: const EdgeInsets.all(20),
+///   crossAxisSpacing: 10,
+///   mainAxisSpacing: 10,
+///   crossAxisCount: 2,
+///   children: <Widget>[
+///     Container(
+///       padding: const EdgeInsets.all(8),
+///       child: const Text("0.He'd have you all unravel at the"),
+///       color: Colors.teal[100],
+///       height: 50.0,
+///     ),
+///     Container(
+///       padding: const EdgeInsets.all(8),
+///       child: const Text('1.Heed not the rabble'),
+///       color: Colors.teal[200],
+///       height: 70.0,
+///     ),
+///     Container(
+///       padding: const EdgeInsets.all(8),
+///       child: const Text('2.Sound of screams but the'),
+///       color: Colors.teal[300],
+///       height: 90.0,
+///     ),
+///     Container(
+///       padding: const EdgeInsets.all(8),
+///       child: const Text('3.Who scream'),
+///       color: Colors.teal[400],
+///       height: 60.0,
+///     ),
+///     Container(
+///       padding: const EdgeInsets.all(8),
+///       child: const Text('4.Revolution is coming...'),
+///       color: Colors.teal[500],
+///       height: 80.0,
+///     ),
+///     Container(
+///       padding: const EdgeInsets.all(8),
+///       child: const Text('5.Revolution, they...'),
+///       color: Colors.teal[600],
+///       height: 100.0,
+///     ),
+///   ],
+/// )
+/// ```
+/// {@end-tool}
+///
+/// {@tool snippet}
+/// This example shows how to create the same grid as the previous example
+/// using a [CustomScrollView] and a [SliverWaterfallFlow].
+///
+/// ![The CustomScrollView contains a SliverWaterfallFlow that displays six children with different background colors and heights arranged in two columns](https://flutter.github.io/assets-for-api-docs/assets/widgets/grid_view_custom_scroll.png)
+///
+/// ```dart
+/// CustomScrollView(
+///   primary: false,
+///   slivers: <Widget>[
+///     SliverPadding(
+///       padding: const EdgeInsets.all(20),
+///       sliver: SliverWaterfallFlow.count(
+///         crossAxisSpacing: 10,
+///         mainAxisSpacing: 10,
+///         crossAxisCount: 2,
+///         children: <Widget>[
+///           Container(
+///             padding: const EdgeInsets.all(8),
+///             child: const Text("0.He'd have you all unravel at the"),
+///             color: Colors.green[100],
+///             height: 50.0,
+///           ),
+///           Container(
+///             padding: const EdgeInsets.all(8),
+///             child: const Text('1.Heed not the rabble'),
+///             color: Colors.green[200],
+///             height: 70.0,
+///           ),
+///           Container(
+///             padding: const EdgeInsets.all(8),
+///             child: const Text('2.Sound of screams but the'),
+///             color: Colors.green[300],
+///             height: 90.0,
+///           ),
+///           Container(
+///             padding: const EdgeInsets.all(8),
+///             child: const Text('3.Who scream'),
+///             color: Colors.green[400],
+///             height: 60.0,
+///           ),
+///           Container(
+///             padding: const EdgeInsets.all(8),
+///             child: const Text('4.Revolution is coming...'),
+///             color: Colors.green[500],
+///             height: 80.0,
+///           ),
+///           Container(
+///             padding: const EdgeInsets.all(8),
+///             child: const Text('5.Revolution, they...'),
+///             color: Colors.green[600],
+///             height: 100.0,
+///           ),
+///         ],
+///       ),
+///     ),
+///   ],
+/// )
+/// ```
+/// {@end-tool}
+///
+/// See also:
+///
+///  * [SingleChildScrollView], which is a scrollable widget that has a single
+///    child.
+///  * [ListView], which is scrollable, linear list of widgets.
+///  * [GridView], which is scrollable, 2D array of widgets.
+///  * [PageView], which is a scrolling list of child widgets that are each the
+///    size of the viewport.
+///  * [CustomScrollView], which is a scrollable widget that creates custom
+///    scroll effects using slivers.
+///  * [SliverGridDelegateWithFixedCrossAxisCount], which creates a layout with
+///    a fixed number of tiles in the cross axis.
+///  * [SliverGridDelegateWithMaxCrossAxisExtent], which creates a layout with
+///    tiles that have a maximum cross-axis extent.
+///  * [ScrollNotification] and [NotificationListener], which can be used to watch
+///    the scroll position without using a [ScrollController].
+class WaterfallFlow extends BoxScrollView {
+  /// Creates a scrollable, 2D array of widgets whose size is variable in the main axis
+  /// with a custom [SliverWaterfallFlowDelegate].
+  ///
+  /// The [gridDelegate] argument must not be null.
+  ///
+  /// The `addAutomaticKeepAlives` argument corresponds to the
+  /// [SliverChildListDelegate.addAutomaticKeepAlives] property. The
+  /// `addRepaintBoundaries` argument corresponds to the
+  /// [SliverChildListDelegate.addRepaintBoundaries] property. Both must not be
+  /// null.
+  WaterfallFlow({
+    Key key,
+    Axis scrollDirection = Axis.vertical,
+    bool reverse = false,
+    ScrollController controller,
+    bool primary,
+    ScrollPhysics physics,
+    bool shrinkWrap = false,
+    EdgeInsetsGeometry padding,
+    @required this.gridDelegate,
+    bool addAutomaticKeepAlives = true,
+    bool addRepaintBoundaries = true,
+    bool addSemanticIndexes = true,
+    double cacheExtent,
+    List<Widget> children = const <Widget>[],
+    int semanticChildCount,
+    DragStartBehavior dragStartBehavior = DragStartBehavior.start,
+    ScrollViewKeyboardDismissBehavior keyboardDismissBehavior =
+        ScrollViewKeyboardDismissBehavior.manual,
+  })  : assert(gridDelegate != null),
+        childrenDelegate = SliverChildListDelegate(
+          children,
+          addAutomaticKeepAlives: addAutomaticKeepAlives,
+          addRepaintBoundaries: addRepaintBoundaries,
+          addSemanticIndexes: addSemanticIndexes,
+        ),
+        super(
+          key: key,
+          scrollDirection: scrollDirection,
+          reverse: reverse,
+          controller: controller,
+          primary: primary,
+          physics: physics,
+          shrinkWrap: shrinkWrap,
+          padding: padding,
+          cacheExtent: cacheExtent,
+          semanticChildCount: semanticChildCount ?? children.length,
+          dragStartBehavior: dragStartBehavior,
+          keyboardDismissBehavior: keyboardDismissBehavior,
+        );
+
+  /// Creates a scrollable, 2D array of widgets whose size is variable in the main axis
+  /// that are created on demand.
+  ///
+  /// This constructor is appropriate for grid views with a large (or infinite)
+  /// number of children because the builder is called only for those children
+  /// that are actually visible.
+  ///
+  /// Providing a non-null `itemCount` improves the ability of the [WaterfallFlow] to
+  /// estimate the maximum scroll extent.
+  ///
+  /// `itemBuilder` will be called only with indices greater than or equal to
+  /// zero and less than `itemCount`.
+  ///
+  /// The [gridDelegate] argument must not be null.
+  ///
+  /// The `addAutomaticKeepAlives` argument corresponds to the
+  /// [SliverChildBuilderDelegate.addAutomaticKeepAlives] property. The
+  /// `addRepaintBoundaries` argument corresponds to the
+  /// [SliverChildBuilderDelegate.addRepaintBoundaries] property. Both must not
+  /// be null.
+  WaterfallFlow.builder({
+    Key key,
+    Axis scrollDirection = Axis.vertical,
+    bool reverse = false,
+    ScrollController controller,
+    bool primary,
+    ScrollPhysics physics,
+    bool shrinkWrap = false,
+    EdgeInsetsGeometry padding,
+    @required this.gridDelegate,
+    @required IndexedWidgetBuilder itemBuilder,
+    int itemCount,
+    bool addAutomaticKeepAlives = true,
+    bool addRepaintBoundaries = true,
+    bool addSemanticIndexes = true,
+    double cacheExtent,
+    int semanticChildCount,
+    DragStartBehavior dragStartBehavior = DragStartBehavior.start,
+    ScrollViewKeyboardDismissBehavior keyboardDismissBehavior =
+        ScrollViewKeyboardDismissBehavior.manual,
+  })  : assert(gridDelegate != null),
+        childrenDelegate = SliverChildBuilderDelegate(
+          itemBuilder,
+          childCount: itemCount,
+          addAutomaticKeepAlives: addAutomaticKeepAlives,
+          addRepaintBoundaries: addRepaintBoundaries,
+          addSemanticIndexes: addSemanticIndexes,
+        ),
+        super(
+          key: key,
+          scrollDirection: scrollDirection,
+          reverse: reverse,
+          controller: controller,
+          primary: primary,
+          physics: physics,
+          shrinkWrap: shrinkWrap,
+          padding: padding,
+          cacheExtent: cacheExtent,
+          semanticChildCount: semanticChildCount ?? itemCount,
+          dragStartBehavior: dragStartBehavior,
+          keyboardDismissBehavior: keyboardDismissBehavior,
+        );
+
+  /// Creates a scrollable, 2D array of widgets whose size is variable in the main axis
+  /// with both a custom [SliverGridDelegate] and a custom [SliverChildDelegate].
+  ///
+  /// To use an [IndexedWidgetBuilder] callback to build children, either use
+  /// a [SliverChildBuilderDelegate] or use the [WaterfallFlow.builder] constructor.
+  ///
+  /// The [gridDelegate] and [childrenDelegate] arguments must not be null.
+  const WaterfallFlow.custom({
+    Key key,
+    Axis scrollDirection = Axis.vertical,
+    bool reverse = false,
+    ScrollController controller,
+    bool primary,
+    ScrollPhysics physics,
+    bool shrinkWrap = false,
+    EdgeInsetsGeometry padding,
+    @required this.gridDelegate,
+    @required this.childrenDelegate,
+    double cacheExtent,
+    int semanticChildCount,
+    DragStartBehavior dragStartBehavior = DragStartBehavior.start,
+    ScrollViewKeyboardDismissBehavior keyboardDismissBehavior =
+        ScrollViewKeyboardDismissBehavior.manual,
+  })  : assert(gridDelegate != null),
+        assert(childrenDelegate != null),
+        super(
+          key: key,
+          scrollDirection: scrollDirection,
+          reverse: reverse,
+          controller: controller,
+          primary: primary,
+          physics: physics,
+          shrinkWrap: shrinkWrap,
+          padding: padding,
+          cacheExtent: cacheExtent,
+          semanticChildCount: semanticChildCount,
+          dragStartBehavior: dragStartBehavior,
+          keyboardDismissBehavior: keyboardDismissBehavior,
+        );
+
+  /// Creates a scrollable, 2D array of widgets whose size is variable in the main axis
+  /// with a fixed number of tiles in the cross axis.
+  ///
+  /// Uses a [SliverWaterfallFlowDelegate] as the [gridDelegate].
+  ///
+  /// The `addAutomaticKeepAlives` argument corresponds to the
+  /// [SliverChildListDelegate.addAutomaticKeepAlives] property. The
+  /// `addRepaintBoundaries` argument corresponds to the
+  /// [SliverChildListDelegate.addRepaintBoundaries] property. Both must not be
+  /// null.
+  ///
+  /// See also:
+  ///
+  ///  * [new SliverWaterfallFlow.count], the equivalent constructor for [SliverWaterfallFlow].
+  WaterfallFlow.count({
+    Key key,
+    Axis scrollDirection = Axis.vertical,
+    bool reverse = false,
+    ScrollController controller,
+    bool primary,
+    ScrollPhysics physics,
+    bool shrinkWrap = false,
+    EdgeInsetsGeometry padding,
+    @required int crossAxisCount,
+    double mainAxisSpacing = 0.0,
+    double crossAxisSpacing = 0.0,
+    bool addAutomaticKeepAlives = true,
+    bool addRepaintBoundaries = true,
+    bool addSemanticIndexes = true,
+    double cacheExtent,
+    List<Widget> children = const <Widget>[],
+    int semanticChildCount,
+    DragStartBehavior dragStartBehavior = DragStartBehavior.start,
+    ScrollViewKeyboardDismissBehavior keyboardDismissBehavior =
+        ScrollViewKeyboardDismissBehavior.manual,
+    LastChildLayoutTypeBuilder lastChildLayoutTypeBuilder,
+    CollectGarbage collectGarbage,
+    ViewportBuilder viewportBuilder,
+    bool closeToTrailing = false,
+  })  : gridDelegate = SliverWaterfallFlowDelegateWithFixedCrossAxisCount(
+          crossAxisCount: crossAxisCount,
+          mainAxisSpacing: mainAxisSpacing,
+          crossAxisSpacing: crossAxisSpacing,
+          lastChildLayoutTypeBuilder: lastChildLayoutTypeBuilder,
+          collectGarbage: collectGarbage,
+          viewportBuilder: viewportBuilder,
+          closeToTrailing: closeToTrailing,
+        ),
+        childrenDelegate = SliverChildListDelegate(
+          children,
+          addAutomaticKeepAlives: addAutomaticKeepAlives,
+          addRepaintBoundaries: addRepaintBoundaries,
+          addSemanticIndexes: addSemanticIndexes,
+        ),
+        super(
+          key: key,
+          scrollDirection: scrollDirection,
+          reverse: reverse,
+          controller: controller,
+          primary: primary,
+          physics: physics,
+          shrinkWrap: shrinkWrap,
+          padding: padding,
+          cacheExtent: cacheExtent,
+          semanticChildCount: semanticChildCount ?? children.length,
+          dragStartBehavior: dragStartBehavior,
+          keyboardDismissBehavior: keyboardDismissBehavior,
+        );
+
+  /// Creates a scrollable, 2D array of widgets in masonry layout with tiles
+  /// that each have a maximum cross-axis extent.
+  ///
+  /// Uses a [SliverMasonryGridDelegateWithMaxCrossAxisExtent] as the [gridDelegate].
+  ///
+  /// The `addAutomaticKeepAlives` argument corresponds to the
+  /// [SliverChildListDelegate.addAutomaticKeepAlives] property. The
+  /// `addRepaintBoundaries` argument corresponds to the
+  /// [SliverChildListDelegate.addRepaintBoundaries] property. Both must not be
+  /// null.
+  ///
+  /// See also:
+  ///
+  ///  * [SliverGrid.extent], the equivalent constructor for [SliverGrid].
+  WaterfallFlow.extent({
+    Key key,
+    Axis scrollDirection = Axis.vertical,
+    bool reverse = false,
+    ScrollController controller,
+    bool primary,
+    ScrollPhysics physics,
+    bool shrinkWrap = false,
+    EdgeInsetsGeometry padding,
+    @required double maxCrossAxisExtent,
+    double mainAxisSpacing = 0.0,
+    double crossAxisSpacing = 0.0,
+    bool addAutomaticKeepAlives = true,
+    bool addRepaintBoundaries = true,
+    bool addSemanticIndexes = true,
+    List<Widget> children = const <Widget>[],
+    int semanticChildCount,
+    DragStartBehavior dragStartBehavior = DragStartBehavior.start,
+    ScrollViewKeyboardDismissBehavior keyboardDismissBehavior =
+        ScrollViewKeyboardDismissBehavior.manual,
+    LastChildLayoutTypeBuilder lastChildLayoutTypeBuilder,
+    CollectGarbage collectGarbage,
+    ViewportBuilder viewportBuilder,
+    bool closeToTrailing = false,
+  })  : gridDelegate = SliverWaterfallFlowDelegateWithMaxCrossAxisExtent(
+          maxCrossAxisExtent: maxCrossAxisExtent,
+          mainAxisSpacing: mainAxisSpacing,
+          crossAxisSpacing: crossAxisSpacing,
+          lastChildLayoutTypeBuilder: lastChildLayoutTypeBuilder,
+          collectGarbage: collectGarbage,
+          viewportBuilder: viewportBuilder,
+          closeToTrailing: closeToTrailing,
+        ),
+        childrenDelegate = SliverChildListDelegate(
+          children,
+          addAutomaticKeepAlives: addAutomaticKeepAlives,
+          addRepaintBoundaries: addRepaintBoundaries,
+          addSemanticIndexes: addSemanticIndexes,
+        ),
+        super(
+          key: key,
+          scrollDirection: scrollDirection,
+          reverse: reverse,
+          controller: controller,
+          primary: primary,
+          physics: physics,
+          shrinkWrap: shrinkWrap,
+          padding: padding,
+          semanticChildCount: semanticChildCount ?? children.length,
+          dragStartBehavior: dragStartBehavior,
+          keyboardDismissBehavior: keyboardDismissBehavior,
+        );
+
+  /// A delegate that controls the masonry layout of the children within the [WaterfallFlow].
+  ///
+  /// The [WaterfallFlow], [WaterfallFlow.builder], and [WaterfallFlow.custom] constructors let you specify this
+  /// delegate explicitly. The other constructors create a [gridDelegate]
+  /// implicitly.
+  final SliverWaterfallFlowDelegate gridDelegate;
+
+  /// A delegate that provides the children for the [WaterfallFlow].
+  ///
+  /// The [WaterfallFlow.custom] constructor lets you specify this delegate
+  /// explicitly. The other constructors create a [childrenDelegate] that wraps
+  /// the given child list.
+  final SliverChildDelegate childrenDelegate;
+
+  @override
+  Widget buildChildLayout(BuildContext context) {
+    return SliverWaterfallFlow(
+      delegate: childrenDelegate,
+      gridDelegate: gridDelegate,
+    );
+  }
+}

lib/src/widgets/sliver.dart

+///
+///  create by zmtzawqlp on 2019/11/9
+///
+import 'package:flutter/widgets.dart' hide ViewportBuilder;
+import 'package:waterfall_flow/src/extended/typedef.dart';
+import 'package:waterfall_flow/src/rendering/sliver_waterfall_flow.dart';
+
+/// A sliver that places multiple box children in a two dimensional arrangement
+/// and masonry layout.
+///
+/// [SliverWaterfallFlow] places its children in arbitrary positions determined by
+/// [gridDelegate]. Each child is forced to have the size specified by the
+/// [gridDelegate].
+///
+/// The main axis direction of a grid is the direction in which it scrolls; the
+/// cross axis direction is the orthogonal direction.
+///
+///
+/// This example, which would be inserted into a [CustomScrollView.slivers]
+/// list, shows twenty boxes in a pretty teal grid with masonry layout:
+///
+/// ```dart
+/// SliverWaterfallFlow(
+///   gridDelegate: SliverWaterfallFlowDelegate(
+///     crossAxisCount: 2,
+///     mainAxisSpacing: 10.0,
+///     crossAxisSpacing: 10.0,
+///   ),
+///   delegate: SliverChildBuilderDelegate(
+///     (BuildContext context, int index) {
+///       return Container(
+///         alignment: Alignment.center,
+///         color: Colors.teal[100 * (index % 9)],
+///         child: Text('grid item $index'),
+///         height: 50.0 + 100.0 * (index % 9)
+///       );
+///     },
+///     childCount: 20,
+///   ),
+/// )
+/// ```
+/// {@end-tool}
+///
+/// {@macro flutter.widgets.sliverChildDelegate.lifecycle}
+///
+/// See also:
+///
+///  * [SliverList], which places its children in a linear array.
+///  * [SliverFixedExtentList], which places its children in a linear
+///    array with a fixed extent in the main axis.
+///  * [SliverPrototypeExtentList], which is similar to [SliverFixedExtentList]
+///    except that it uses a prototype list item instead of a pixel value to define
+///    the main axis extent of each item.
+///  * [SliverGrid], which places its children in arbitrary positions.
+class SliverWaterfallFlow extends SliverMultiBoxAdaptorWidget {
+  /// Creates a sliver that places multiple box children in a two dimensional
+  /// arrangement and masonry layout.
+  const SliverWaterfallFlow({
+    Key key,
+    @required SliverChildDelegate delegate,
+    @required this.gridDelegate,
+  }) : super(key: key, delegate: delegate);
+
+  /// Creates a sliver that places multiple box children in a two dimensional
+  /// arrangement and masonry layout with a fixed number of tiles in the cross axis.
+  ///
+  /// Uses a [SliverWaterfallFlowDelegate] as the [gridDelegate],
+  /// and a [SliverChildListDelegate] as the [delegate].
+  ///
+  /// See also:
+  ///
+  ///  * [new WaterfallFlow.count], the equivalent constructor for [WaterfallFlow] widgets.
+  SliverWaterfallFlow.count({
+    Key key,
+    @required int crossAxisCount,
+    double mainAxisSpacing = 0.0,
+    double crossAxisSpacing = 0.0,
+    List<Widget> children = const <Widget>[],
+    LastChildLayoutTypeBuilder lastChildLayoutTypeBuilder,
+    CollectGarbage collectGarbage,
+    ViewportBuilder viewportBuilder,
+    bool closeToTrailing = false,
+  })  : gridDelegate = SliverWaterfallFlowDelegateWithFixedCrossAxisCount(
+          crossAxisCount: crossAxisCount,
+          mainAxisSpacing: mainAxisSpacing,
+          crossAxisSpacing: crossAxisSpacing,
+          lastChildLayoutTypeBuilder: lastChildLayoutTypeBuilder,
+          collectGarbage: collectGarbage,
+          viewportBuilder: viewportBuilder,
+          closeToTrailing: closeToTrailing,
+        ),
+        super(key: key, delegate: SliverChildListDelegate(children));
+
+  /// Creates a sliver that places multiple box children in masonry layout
+  /// with tiles that each have a maximum cross-axis extent.
+  ///
+  /// Uses a [SliverMasonryGridDelegateWithMaxCrossAxisExtent] as the [gridDelegate],
+  /// and a [SliverChildListDelegate] as the [delegate].
+  ///
+  /// See also:
+  ///
+  ///  * [new MasonryGridView.extent], the equivalent constructor for [MasonryGridView] widgets.
+  SliverWaterfallFlow.extent({
+    Key key,
+    @required double maxCrossAxisExtent,
+    double mainAxisSpacing = 0.0,
+    double crossAxisSpacing = 0.0,
+    List<Widget> children = const <Widget>[],
+    LastChildLayoutTypeBuilder lastChildLayoutTypeBuilder,
+    CollectGarbage collectGarbage,
+    ViewportBuilder viewportBuilder,
+    bool closeToTrailing = false,
+  })  : gridDelegate = SliverWaterfallFlowDelegateWithMaxCrossAxisExtent(
+          maxCrossAxisExtent: maxCrossAxisExtent,
+          mainAxisSpacing: mainAxisSpacing,
+          crossAxisSpacing: crossAxisSpacing,
+          lastChildLayoutTypeBuilder: lastChildLayoutTypeBuilder,
+          collectGarbage: collectGarbage,
+          viewportBuilder: viewportBuilder,
+          closeToTrailing: closeToTrailing,
+        ),
+        super(key: key, delegate: SliverChildListDelegate(children));
+
+  /// The delegate that controls the size and position of the children.
+  final SliverWaterfallFlowDelegate gridDelegate;
+
+  @override
+  RenderSliverWaterfallFlow createRenderObject(BuildContext context) {
+    final SliverMultiBoxAdaptorElement element = context as SliverMultiBoxAdaptorElement;
+    return RenderSliverWaterfallFlow(childManager: element, gridDelegate: gridDelegate);
+  }
+
+  @override
+  void updateRenderObject(BuildContext context, RenderSliverWaterfallFlow renderObject) {
+    renderObject.gridDelegate = gridDelegate;
+  }
+}

lib/waterfall_flow.dart

+library waterfall_flow;
+
+export 'src/extended/extended_list_library.dart';
+export 'src/rendering/sliver_waterfall_flow.dart';
+export 'src/widgets/scroll_view.dart';
+export 'src/widgets/sliver.dart';
+export 'xxwaterfall_flow.dart';
\ No newline at end of file

lib/xxwaterfall_flow.dart

+import 'package:flutter/widgets.dart';
+import 'package:waterfall_flow/src/widgets/scroll_view.dart';
+import 'src/rendering/sliver_waterfall_flow.dart';
+
+class XXSliverWaterFallFlow extends StatefulWidget {
+  final Widget Function(BuildContext, int) itemBuilder;
+  final void Function(int firstIndex, int lastIndex) onScrollInit;
+  final void Function(int firstIndex, int lastIndex) onScrollEnd;
+  const XXSliverWaterFallFlow({ Key key,@required this.itemBuilder,this.onScrollInit,this.onScrollEnd}) : super(key: key);
+
+  @override
+  _XXSliverWaterFallFlowState createState() => _XXSliverWaterFallFlowState();
+}
+
+class _XXSliverWaterFallFlowState extends State<XXSliverWaterFallFlow> {
+
+  bool _isInit = true;
+  int _firstIndex;
+  int _lastIndex;
+
+  @override
+  Widget build(BuildContext context) {
+    return NotificationListener<ScrollNotification>(
+      onNotification: (ScrollNotification notification) {
+        if (notification.runtimeType == ScrollEndNotification) {
+          if(widget.onScrollEnd != null){
+            widget.onScrollEnd(_firstIndex,_lastIndex);
+          }
+        }
+        return true;
+      },
+      child:WaterfallFlow.builder(
+        gridDelegate:SliverWaterfallFlowDelegateWithFixedCrossAxisCount(
+          crossAxisCount: 5,
+          crossAxisSpacing: 5.0,
+          mainAxisSpacing: 5.0,
+          viewportBuilder:(int firstIndex, int lastIndex) {
+            _firstIndex = firstIndex;
+            _lastIndex = lastIndex;
+            if(_isInit && widget.onScrollInit != null){
+              widget.onScrollInit(_firstIndex,_lastIndex);
+              _isInit = false;
+            }
+          }
+        ),
+        itemBuilder:widget.itemBuilder,
+      ),
+    );
+  }
+}
\ No newline at end of file

pubspec.yaml

+name: waterfall_flow
+description: A Flutter grid view that build waterfall flow layout quickly.
+version: 2.0.5
+homepage: https://github.com/fluttercandies/waterfall_flow
+
+environment:
+  sdk: ">=2.6.0 <3.0.0"
+  flutter: ">=1.22.4"
+
+dependencies:
+  flutter:
+    sdk: flutter
+
+dev_dependencies:
+  flutter_test:
+    sdk: flutter
+
+flutter:
\ No newline at end of file

test/rendering/sliver_waterfall_flow_test.dart

+// @dart = 2.8
+import 'package:flutter_test/flutter_test.dart';
+import 'package:flutter/material.dart';
+import 'package:waterfall_flow/waterfall_flow.dart';
+
+void main() {
+  group('SliverWaterfallFlow', () {
+    testWidgets('the size of each child', (WidgetTester tester) async {
+      await tester.pumpWidget(materialAppBoilerplate(
+        child: customScrollViewBoilerplate(
+          sliverMasonryGrid:
+              sliverMasonryGridWithChildrenBoilerplate(crossAxisCount: 2),
+        ),
+        textDirection: TextDirection.ltr,
+      ));
+
+      expect(
+        tester.getSize(find.widgetWithText(
+            Container, "0.He'd have you all unravel at the")),
+        const Size(400.0, 50.0),
+      );
+
+      expect(
+        tester.getSize(find.widgetWithText(Container, '1.Heed not the rabble')),
+        const Size(400.0, 70.0),
+      );
+
+      expect(
+        tester.getSize(
+            find.widgetWithText(Container, '2.Sound of screams but the')),
+        const Size(400.0, 90.0),
+      );
+
+      expect(
+        tester.getSize(find.widgetWithText(Container, '3.Who scream')),
+        const Size(400.0, 60.0),
+      );
+
+      expect(
+        tester.getSize(
+            find.widgetWithText(Container, '4.Revolution is coming...')),
+        const Size(400.0, 80.0),
+      );
+
+      expect(
+        tester.getSize(find.widgetWithText(Container, '5.Revolution, they...')),
+        const Size(400.0, 100.0),
+      );
+    });
+
+    testWidgets('the position of each child at TextDirection.ltr',
+        (WidgetTester tester) async {
+      await tester.pumpWidget(materialAppBoilerplate(
+        child: customScrollViewBoilerplate(
+          sliverMasonryGrid:
+              sliverMasonryGridWithChildrenBoilerplate(crossAxisCount: 2),
+        ),
+        textDirection: TextDirection.ltr,
+      ));
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(
+            Container, "0.He'd have you all unravel at the")),
+        const Offset(0.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '1.Heed not the rabble')),
+        const Offset(400.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '2.Sound of screams but the')),
+        const Offset(0.0, 50.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3.Who scream')),
+        const Offset(400.0, 70.0),
+      );
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '4.Revolution is coming...')),
+        const Offset(400.0, 130.0),
+      );
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '5.Revolution, they...')),
+        const Offset(0.0, 140.0),
+      );
+    });
+
+    testWidgets('the position of each child at TextDirection.rtl',
+        (WidgetTester tester) async {
+      await tester.pumpWidget(
+        materialAppBoilerplate(
+            child: customScrollViewBoilerplate(
+              sliverMasonryGrid:
+                  sliverMasonryGridWithChildrenBoilerplate(crossAxisCount: 2),
+            ),
+            textDirection: TextDirection.rtl),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(
+            Container, "0.He'd have you all unravel at the")),
+        const Offset(400.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '1.Heed not the rabble')),
+        const Offset(0.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '2.Sound of screams but the')),
+        const Offset(400.0, 50.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3.Who scream')),
+        const Offset(0.0, 70.0),
+      );
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '4.Revolution is coming...')),
+        const Offset(0.0, 130.0),
+      );
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '5.Revolution, they...')),
+        const Offset(400.0, 140.0),
+      );
+    });
+
+    testWidgets('crossAxisCount change test', (WidgetTester tester) async {
+      int crossAxisCount = 2;
+      await tester.pumpWidget(
+        materialAppBoilerplate(
+            child: SliverMasonryTestPage(
+              crossAxisCount: crossAxisCount,
+              setState: (_SliverMasonryTestPageState state) {
+                state._crossAxisCount = crossAxisCount;
+              },
+            ),
+            textDirection: TextDirection.ltr),
+      );
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '2.Sound of screams but the')),
+        const Offset(0.0, 50.0),
+      );
+
+      crossAxisCount = 4;
+      await setStateBoilerplate(tester);
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '2.Sound of screams but the')),
+        const Offset(400.0, 0.0),
+      );
+    });
+
+    testWidgets('crossAxisSpacing change test', (WidgetTester tester) async {
+      double crossAxisSpacing = 10;
+      await tester.pumpWidget(
+        materialAppBoilerplate(
+            child: SliverMasonryTestPage(
+              crossAxisSpacing: crossAxisSpacing,
+              crossAxisCount: 2,
+              setState: (_SliverMasonryTestPageState state) {
+                state._crossAxisSpacing = crossAxisSpacing;
+              },
+            ),
+            textDirection: TextDirection.ltr),
+      );
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '2.Sound of screams but the')),
+        const Offset(0.0, 50.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3.Who scream')),
+        const Offset(405.0, 70.0),
+      );
+
+      crossAxisSpacing = 20;
+      await setStateBoilerplate(tester);
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '2.Sound of screams but the')),
+        const Offset(0.0, 50.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3.Who scream')),
+        const Offset(410.0, 70.0),
+      );
+    });
+
+    testWidgets('mainAxisSpacing test', (WidgetTester tester) async {
+      double mainAxisSpacing = 10;
+      await tester.pumpWidget(
+        materialAppBoilerplate(
+            child: SliverMasonryTestPage(
+              mainAxisSpacing: mainAxisSpacing,
+              crossAxisCount: 2,
+              setState: (_SliverMasonryTestPageState state) {
+                state._mainAxisSpacing = mainAxisSpacing;
+              },
+            ),
+            textDirection: TextDirection.ltr),
+      );
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '2.Sound of screams but the')),
+        const Offset(0.0, 60.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3.Who scream')),
+        const Offset(400.0, 80.0),
+      );
+
+      mainAxisSpacing = 20;
+      await setStateBoilerplate(tester);
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '2.Sound of screams but the')),
+        const Offset(0.0, 70.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3.Who scream')),
+        const Offset(400.0, 90.0),
+      );
+    });
+
+    testWidgets('maxCrossAxisExtent change test', (WidgetTester tester) async {
+      double maxCrossAxisExtent = 400;
+      await tester.pumpWidget(
+        materialAppBoilerplate(
+            child: SliverMasonryTestPage(
+              maxCrossAxisExtent: maxCrossAxisExtent,
+              crossAxisCount: 2,
+              setState: (_SliverMasonryTestPageState state) {
+                state._maxCrossAxisExtent = maxCrossAxisExtent;
+              },
+            ),
+            textDirection: TextDirection.ltr),
+      );
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '2.Sound of screams but the')),
+        const Offset(0.0, 50.0),
+      );
+
+      maxCrossAxisExtent = 200;
+      await setStateBoilerplate(tester);
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '2.Sound of screams but the')),
+        const Offset(400.0, 0.0),
+      );
+    });
+
+    testWidgets('itemCount change test', (WidgetTester tester) async {
+      final ScrollController controller = ScrollController();
+      int itemCount = 100;
+      await tester.pumpWidget(
+        materialAppBoilerplate(
+            child: SliverMasonryTestPage(
+          controller: controller,
+          crossAxisCount: 4,
+          items: List<int>.generate(itemCount, (int index) => index),
+          setState: (_SliverMasonryTestPageState state) {
+            state._items = List<int>.generate(itemCount, (int index) => index);
+          },
+          builder: true,
+        )),
+      );
+      expect(find.widgetWithText(Container, '0'), findsOneWidget);
+      controller.jumpTo(10000);
+      await tester.pumpAndSettle();
+
+      itemCount = 0;
+      await setStateBoilerplate(tester);
+
+      expect(find.widgetWithText(Container, '0'), findsNothing);
+      expect(controller.offset, 0.0);
+
+      itemCount = 100;
+      await setStateBoilerplate(tester);
+
+      expect(find.widgetWithText(Container, '3'), findsOneWidget);
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '0')),
+        const Offset(0.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '1')),
+        const Offset(200.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '2')),
+        const Offset(400.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3')),
+        const Offset(600.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '4')),
+        const Offset(0.0, 100.0),
+      );
+    });
+
+    testWidgets('items removeRange test', (WidgetTester tester) async {
+      final ScrollController controller = ScrollController();
+      int start;
+      int end;
+      await tester.pumpWidget(
+        materialAppBoilerplate(
+            child: SliverMasonryTestPage(
+          controller: controller,
+          crossAxisCount: 4,
+          items: List<int>.generate(100, (int index) => index),
+          setState: (_SliverMasonryTestPageState state) {
+            state._items.removeRange(start, end);
+          },
+          builder: true,
+        )),
+      );
+      expect(find.widgetWithText(Container, '0'), findsOneWidget);
+      controller.jumpTo(10000);
+      await tester.pumpAndSettle();
+
+      start = 40;
+      end = 60;
+      await setStateBoilerplate(tester);
+      controller.jumpTo(0);
+      await tester.pumpAndSettle();
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '0')),
+        const Offset(0.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '1')),
+        const Offset(200.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '2')),
+        const Offset(400.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3')),
+        const Offset(600.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '4')),
+        const Offset(0.0, 100.0),
+      );
+    });
+
+    // code coverage: [RenderSliverMasonryGrid]
+    // if (data.layoutOffset < -precisionErrorTolerance)
+    testWidgets('the child who out of viewport change big test',
+        (WidgetTester tester) async {
+      final ScrollController controller = ScrollController();
+      double size;
+      await tester.pumpWidget(
+        materialAppBoilerplate(
+            child: SliverMasonryTestPage(
+          controller: controller,
+          crossAxisCount: 4,
+          items: List<int>.generate(100, (int index) => index),
+          sizeBuilder: (int index) {
+            if (index == 1 && size != null) {
+              return size;
+            }
+            return null;
+          },
+          builder: true,
+        )),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '0')),
+        const Offset(0.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '1')),
+        const Offset(200.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '2')),
+        const Offset(400.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3')),
+        const Offset(600.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '4')),
+        const Offset(0.0, 100.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '5')),
+        const Offset(0.0, 200.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '6')),
+        const Offset(200.0, 200.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '7')),
+        const Offset(400.0, 300.0),
+      );
+
+      controller.jumpTo(10000);
+      await tester.pumpAndSettle();
+      expect(find.widgetWithText(Container, '0'), findsNothing);
+
+      // change child size from 200 to 500.
+      size = 500;
+      await setStateBoilerplate(tester);
+      controller.jumpTo(0);
+      await tester.pumpAndSettle();
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '0')),
+        const Offset(0.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '1')),
+        const Offset(200.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '2')),
+        const Offset(400.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3')),
+        const Offset(600.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '4')),
+        const Offset(0.0, 100.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '5')),
+        const Offset(0.0, 200.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '6')),
+        const Offset(400.0, 300.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '7')),
+        const Offset(0.0, 400.0),
+      );
+    });
+
+    // code coverage: [RenderSliverMasonryGrid]
+    // if (earliestUsefulChild == null) {
+    testWidgets('the child who out of viewport change small sroll into 0 test',
+        (WidgetTester tester) async {
+      final ScrollController controller = ScrollController();
+      double size;
+      await tester.pumpWidget(
+        materialAppBoilerplate(
+            child: SliverMasonryTestPage(
+          controller: controller,
+          crossAxisCount: 4,
+          items: List<int>.generate(100, (int index) => index),
+          sizeBuilder: (int index) {
+            if (index == 0 && size != null) {
+              return size;
+            }
+            return null;
+          },
+          builder: true,
+        )),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '0')),
+        const Offset(0.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '1')),
+        const Offset(200.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '2')),
+        const Offset(400.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3')),
+        const Offset(600.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '4')),
+        const Offset(0.0, 100.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '5')),
+        const Offset(0.0, 200.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '6')),
+        const Offset(200.0, 200.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '7')),
+        const Offset(400.0, 300.0),
+      );
+
+      controller.jumpTo(10000);
+      await tester.pumpAndSettle();
+      expect(find.widgetWithText(Container, '0'), findsNothing);
+
+      // change child size from 100 to 30.
+      size = 30;
+      await setStateBoilerplate(tester);
+      controller.jumpTo(0);
+      await tester.pumpAndSettle();
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '0')),
+        const Offset(0.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '1')),
+        const Offset(200.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '2')),
+        const Offset(400.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3')),
+        const Offset(600.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '4')),
+        const Offset(0.0, 30.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '5')),
+        const Offset(0.0, 130.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '6')),
+        const Offset(200.0, 200.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '7')),
+        const Offset(400.0, 300.0),
+      );
+    });
+
+    // code coverage: [RenderSliverMasonryGrid]
+    // if (earliestUsefulChild == null) {
+    testWidgets(
+        'the child who out of viewport change small sroll into 100 test',
+        (WidgetTester tester) async {
+      final ScrollController controller = ScrollController();
+      double size;
+      await tester.pumpWidget(
+        materialAppBoilerplate(
+            child: SliverMasonryTestPage(
+          controller: controller,
+          crossAxisCount: 4,
+          items: List<int>.generate(100, (int index) => index),
+          sizeBuilder: (int index) {
+            if (index == 1 && size != null) {
+              return size;
+            }
+            return null;
+          },
+          builder: true,
+        )),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '0')),
+        const Offset(0.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '1')),
+        const Offset(200.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '2')),
+        const Offset(400.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3')),
+        const Offset(600.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '4')),
+        const Offset(0.0, 100.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '5')),
+        const Offset(0.0, 200.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '6')),
+        const Offset(200.0, 200.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '7')),
+        const Offset(400.0, 300.0),
+      );
+
+      controller.jumpTo(10000);
+      await tester.pumpAndSettle();
+      expect(find.widgetWithText(Container, '0'), findsNothing);
+
+      // change child size from 100 to 30.
+      size = 30;
+      await setStateBoilerplate(tester);
+      controller.jumpTo(100);
+      await tester.pumpAndSettle();
+
+      expect(find.widgetWithText(Container, '0'), findsNothing);
+
+      expect(find.widgetWithText(Container, '1'), findsNothing);
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '2')),
+        const Offset(400.0, -100.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3')),
+        const Offset(600.0, -100.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '4')),
+        const Offset(200.0, -70.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '5')),
+        const Offset(0.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '6')),
+        const Offset(200.0, 30.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '7')),
+        const Offset(0.0, 200.0),
+      );
+    });
+
+    // code coverage: [RenderSliverMasonryGrid]
+    // if (data.layoutOffset < -precisionErrorTolerance)
+    testWidgets('insert child out of viewport test',
+        (WidgetTester tester) async {
+      final ScrollController controller = ScrollController();
+      double size;
+      await tester.pumpWidget(
+        materialAppBoilerplate(
+            child: SliverMasonryTestPage(
+          controller: controller,
+          crossAxisCount: 4,
+          items: List<int>.generate(100, (int index) => index),
+          sizeBuilder: (int index) {
+            if (index == 0 && size != null) {
+              return size;
+            }
+            return null;
+          },
+          setState: (_SliverMasonryTestPageState state) {
+            state._items.insert(0, 999);
+          },
+          builder: true,
+        )),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '0')),
+        const Offset(0.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '1')),
+        const Offset(200.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '2')),
+        const Offset(400.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3')),
+        const Offset(600.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '4')),
+        const Offset(0.0, 100.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '5')),
+        const Offset(0.0, 200.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '6')),
+        const Offset(200.0, 200.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '7')),
+        const Offset(400.0, 300.0),
+      );
+
+      controller.jumpTo(10000);
+      await tester.pumpAndSettle();
+      expect(find.widgetWithText(Container, '0'), findsNothing);
+
+      // insert 999 into 0 index with size 500.0.
+      size = 500;
+      await setStateBoilerplate(tester);
+      controller.jumpTo(0);
+      await tester.pumpAndSettle();
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '999')),
+        const Offset(0.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '0')),
+        const Offset(200.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '1')),
+        const Offset(400.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '2')),
+        const Offset(600.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3')),
+        const Offset(200.0, 200.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '4')),
+        const Offset(200.0, 300.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '5')),
+        const Offset(400.0, 300.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '7')),
+        const Offset(0.0, 500.0),
+      );
+    });
+
+    testWidgets('remove child out of viewport test',
+        (WidgetTester tester) async {
+      final ScrollController controller = ScrollController();
+      int removeIndex;
+      await tester.pumpWidget(
+        materialAppBoilerplate(
+            child: SliverMasonryTestPage(
+          controller: controller,
+          crossAxisCount: 4,
+          items: List<int>.generate(100, (int index) => index),
+          sizeBuilder: (int index) {
+            if (removeIndex != null && index >= removeIndex) {
+              return (((index + 1) % 4) + 1) * 100.0;
+            }
+            return null;
+          },
+          setState: (_SliverMasonryTestPageState state) {
+            state._items.remove(removeIndex);
+          },
+          builder: true,
+        )),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '0')),
+        const Offset(0.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '1')),
+        const Offset(200.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '2')),
+        const Offset(400.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3')),
+        const Offset(600.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '4')),
+        const Offset(0.0, 100.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '5')),
+        const Offset(0.0, 200.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '6')),
+        const Offset(200.0, 200.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '7')),
+        const Offset(400.0, 300.0),
+      );
+
+      controller.jumpTo(10000);
+      await tester.pumpAndSettle();
+      expect(find.widgetWithText(Container, '0'), findsNothing);
+
+      // remove index 3.
+      removeIndex = 3;
+      await setStateBoilerplate(tester);
+      controller.jumpTo(0);
+      await tester.pumpAndSettle();
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '0')),
+        const Offset(0.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '1')),
+        const Offset(200.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '2')),
+        const Offset(400.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '4')),
+        const Offset(600.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '5')),
+        const Offset(0.0, 100.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '6')),
+        const Offset(600.0, 100.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '7')),
+        const Offset(200.0, 200.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '8')),
+        const Offset(0.0, 300.0),
+      );
+    });
+
+    testWidgets('test with other slivers', (WidgetTester tester) async {
+      await tester.pumpWidget(
+        materialAppBoilerplate(
+            child: SliverMasonryTestPage(
+              crossAxisCount: 2,
+              headerSlivers: <Widget>[
+                SliverToBoxAdapter(
+                  child: Container(
+                    height: 200.0,
+                    color: Colors.red,
+                  ),
+                )
+              ],
+              footSlivers: <Widget>[
+                SliverToBoxAdapter(
+                  child: Container(
+                    height: 200.0,
+                    color: Colors.blue,
+                  ),
+                )
+              ],
+            ),
+            textDirection: TextDirection.ltr),
+      );
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '2.Sound of screams but the')),
+        const Offset(0.0, 250.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3.Who scream')),
+        const Offset(400.0, 270.0),
+      );
+    });
+
+    testWidgets('insert other slivers test', (WidgetTester tester) async {
+      final ScrollController controller = ScrollController();
+      await tester.pumpWidget(
+        materialAppBoilerplate(
+            child: SliverMasonryTestPage(
+              controller: controller,
+              crossAxisCount: 2,
+              headerSlivers: <Widget>[
+                SliverToBoxAdapter(
+                  child: Container(
+                    height: 200.0,
+                    color: Colors.red,
+                  ),
+                )
+              ],
+              footSlivers: <Widget>[
+                SliverToBoxAdapter(
+                  child: Container(
+                    height: 200.0,
+                    color: Colors.blue,
+                  ),
+                )
+              ],
+              setState: (_SliverMasonryTestPageState state) {
+                state._headerSlivers.add(
+                  SliverToBoxAdapter(
+                    child: Container(
+                      height: 200.0,
+                      color: Colors.yellow,
+                    ),
+                  ),
+                );
+              },
+            ),
+            textDirection: TextDirection.ltr),
+      );
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '2.Sound of screams but the')),
+        const Offset(0.0, 250.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3.Who scream')),
+        const Offset(400.0, 270.0),
+      );
+
+      controller.jumpTo(10000);
+      await tester.pumpAndSettle();
+      expect(
+          find.widgetWithText(Container, "0.He'd have you all unravel at the"),
+          findsOneWidget);
+
+      await setStateBoilerplate(tester);
+      controller.jumpTo(0);
+      await tester.pumpAndSettle();
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(
+            Container, "0.He'd have you all unravel at the")),
+        const Offset(0.0, 400.0),
+      );
+    });
+  });
+}
+
+SliverWaterfallFlow masonryGridBoilerplate({
+  int crossAxisCount = 4,
+  double crossAxisSpacing = 0.0,
+  double mainAxisSpacing = 0.0,
+  double maxCrossAxisExtent,
+  List<int> items,
+  double Function(int index) sizeBuilder,
+}) {
+  final SliverWaterfallFlowDelegate delegate = maxCrossAxisExtent != null
+      ? SliverWaterfallFlowDelegateWithMaxCrossAxisExtent(
+          maxCrossAxisExtent: maxCrossAxisExtent,
+          mainAxisSpacing: mainAxisSpacing,
+          crossAxisSpacing: crossAxisSpacing,
+        )
+      : SliverWaterfallFlowDelegateWithFixedCrossAxisCount(
+          crossAxisCount: crossAxisCount,
+          mainAxisSpacing: mainAxisSpacing,
+          crossAxisSpacing: crossAxisSpacing,
+        );
+
+  return SliverWaterfallFlow(
+    gridDelegate: delegate,
+    delegate: SliverChildBuilderDelegate(
+      (BuildContext context, int index) {
+        return Container(
+          alignment: Alignment.center,
+          child: Text(
+            '${items[index]}',
+          ),
+          height: sizeBuilder?.call(index) ??
+              ((index % crossAxisCount) + 1) * 100.0,
+        );
+      },
+      childCount: items.length,
+    ),
+  );
+}
+
+SliverWaterfallFlow sliverMasonryGridWithChildrenBoilerplate({
+  int crossAxisCount = 2,
+  double crossAxisSpacing = 0.0,
+  double mainAxisSpacing = 0.0,
+  double maxCrossAxisExtent,
+}) {
+  final List<Widget> children = <Widget>[
+    Container(
+      padding: const EdgeInsets.all(8),
+      child: const Text("0.He'd have you all unravel at the"),
+      color: Colors.teal[100],
+      height: 50.0,
+    ),
+    Container(
+      padding: const EdgeInsets.all(8),
+      child: const Text('1.Heed not the rabble'),
+      color: Colors.teal[200],
+      height: 70.0,
+    ),
+    Container(
+      padding: const EdgeInsets.all(8),
+      child: const Text('2.Sound of screams but the'),
+      color: Colors.teal[300],
+      height: 90.0,
+    ),
+    Container(
+      padding: const EdgeInsets.all(8),
+      child: const Text('3.Who scream'),
+      color: Colors.teal[400],
+      height: 60.0,
+    ),
+    Container(
+      padding: const EdgeInsets.all(8),
+      child: const Text('4.Revolution is coming...'),
+      color: Colors.teal[500],
+      height: 80.0,
+    ),
+    Container(
+      padding: const EdgeInsets.all(8),
+      child: const Text('5.Revolution, they...'),
+      color: Colors.teal[600],
+      height: 100.0,
+    ),
+  ];
+
+  return maxCrossAxisExtent != null
+      ? SliverWaterfallFlow.extent(
+          maxCrossAxisExtent: maxCrossAxisExtent,
+          crossAxisSpacing: crossAxisSpacing,
+          mainAxisSpacing: mainAxisSpacing,
+          children: children,
+        )
+      : SliverWaterfallFlow.count(
+          crossAxisCount: crossAxisCount,
+          crossAxisSpacing: crossAxisSpacing,
+          mainAxisSpacing: mainAxisSpacing,
+          children: children,
+        );
+}
+
+Widget customScrollViewBoilerplate({
+  List<Widget> headerSlivers,
+  List<Widget> footSlivers,
+  SliverWaterfallFlow sliverMasonryGrid,
+  ScrollController controller,
+}) {
+  return CustomScrollView(
+    controller: controller,
+    slivers: <Widget>[
+      if (headerSlivers != null) ...headerSlivers,
+      sliverMasonryGrid,
+      if (footSlivers != null) ...footSlivers,
+    ],
+  );
+}
+
+Widget materialAppBoilerplate({
+  Widget child,
+  TextDirection textDirection = TextDirection.ltr,
+}) {
+  return MaterialApp(
+    home: Directionality(
+      textDirection: textDirection,
+      child: MediaQuery(
+        data: const MediaQueryData(size: Size(800.0, 600.0)),
+        child: Material(
+          child: child,
+        ),
+      ),
+    ),
+  );
+}
+
+class SliverMasonryTestPage extends StatefulWidget {
+  const SliverMasonryTestPage({
+    this.crossAxisCount = 4,
+    this.mainAxisSpacing = 0.0,
+    this.crossAxisSpacing = 0.0,
+    this.textDirection = TextDirection.ltr,
+    this.maxCrossAxisExtent,
+    this.items,
+    this.controller,
+    this.setState,
+    this.builder = false,
+    this.headerSlivers,
+    this.footSlivers,
+    this.sizeBuilder,
+  });
+  final int crossAxisCount;
+  final double mainAxisSpacing;
+  final double crossAxisSpacing;
+  final TextDirection textDirection;
+  final double maxCrossAxisExtent;
+  final List<int> items;
+  final ScrollController controller;
+  final void Function(_SliverMasonryTestPageState setState) setState;
+  final bool builder;
+  final List<Widget> headerSlivers;
+  final List<Widget> footSlivers;
+  final double Function(int index) sizeBuilder;
+  @override
+  _SliverMasonryTestPageState createState() => _SliverMasonryTestPageState();
+}
+
+class _SliverMasonryTestPageState extends State<SliverMasonryTestPage> {
+  int _crossAxisCount;
+  double _crossAxisSpacing;
+  double _mainAxisSpacing;
+  TextDirection _textDirection;
+  double _maxCrossAxisExtent;
+  List<Widget> _headerSlivers;
+  List<Widget> _footSlivers;
+  List<int> _items;
+  @override
+  void initState() {
+    _crossAxisCount = widget.crossAxisCount;
+    _mainAxisSpacing = widget.mainAxisSpacing;
+    _crossAxisSpacing = widget.crossAxisSpacing;
+    _textDirection = widget.textDirection;
+    _maxCrossAxisExtent = widget.maxCrossAxisExtent;
+    _items = widget.items;
+    _headerSlivers = widget.headerSlivers;
+    _footSlivers = widget.footSlivers;
+    super.initState();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      body: Directionality(
+          textDirection: _textDirection,
+          child: customScrollViewBoilerplate(
+            controller: widget.controller,
+            headerSlivers: _headerSlivers,
+            footSlivers: _footSlivers,
+            sliverMasonryGrid: widget.builder
+                ? masonryGridBoilerplate(
+                    crossAxisCount: _crossAxisCount,
+                    mainAxisSpacing: _mainAxisSpacing,
+                    crossAxisSpacing: _crossAxisSpacing,
+                    maxCrossAxisExtent: _maxCrossAxisExtent,
+                    items: _items,
+                    sizeBuilder: widget.sizeBuilder,
+                  )
+                : sliverMasonryGridWithChildrenBoilerplate(
+                    crossAxisCount: _crossAxisCount,
+                    mainAxisSpacing: _mainAxisSpacing,
+                    crossAxisSpacing: _crossAxisSpacing,
+                    maxCrossAxisExtent: _maxCrossAxisExtent,
+                  ),
+          )),
+      floatingActionButton: FloatingActionButton(
+        onPressed: () {
+          setState(() {
+            widget.setState?.call(this);
+          });
+        },
+        child: const Icon(Icons.add),
+      ),
+    );
+  }
+}
+
+Future<void> setStateBoilerplate(WidgetTester tester) async {
+  await tester.tap(find.byType(FloatingActionButton));
+  await tester.pumpAndSettle();
+}

test/states.dart

+const List<String> kStates = <String>[
+  'Alabama',
+  'Alaska',
+  'Arizona',
+  'Arkansas',
+  'California',
+  'Colorado',
+  'Connecticut',
+  'Delaware',
+  'Florida',
+  'Georgia',
+  'Hawaii',
+  'Idaho',
+  'Illinois',
+  'Indiana',
+  'Iowa',
+  'Kansas',
+  'Kentucky',
+  'Louisiana',
+  'Maine',
+  'Maryland',
+  'Massachusetts',
+  'Michigan',
+  'Minnesota',
+  'Mississippi',
+  'Missouri',
+  'Montana',
+  'Nebraska',
+  'Nevada',
+  'New Hampshire',
+  'New Jersey',
+  'New Mexico',
+  'New York',
+  'North Carolina',
+  'North Dakota',
+  'Ohio',
+  'Oklahoma',
+  'Oregon',
+  'Pennsylvania',
+  'Rhode Island',
+  'South Carolina',
+  'South Dakota',
+  'Tennessee',
+  'Texas',
+  'Utah',
+  'Vermont',
+  'Virginia',
+  'Washington',
+  'West Virginia',
+  'Wisconsin',
+  'Wyoming',
+];

test/widgets/waterfall_flow_test.dart

+// @dart = 2.8
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:flutter/material.dart';
+import 'package:waterfall_flow/waterfall_flow.dart';
+
+void main() {
+  group('WaterfallFlow', () {
+    testWidgets('the size of each child', (WidgetTester tester) async {
+      await tester.pumpWidget(materialAppBoilerplate(
+        child: masonryGridViewWithChildrenBoilerplate(crossAxisCount: 2),
+        textDirection: TextDirection.ltr,
+      ));
+
+      expect(
+        tester.getSize(find.widgetWithText(
+            Container, "0.He'd have you all unravel at the")),
+        const Size(400.0, 50.0),
+      );
+
+      expect(
+        tester.getSize(find.widgetWithText(Container, '1.Heed not the rabble')),
+        const Size(400.0, 70.0),
+      );
+
+      expect(
+        tester.getSize(
+            find.widgetWithText(Container, '2.Sound of screams but the')),
+        const Size(400.0, 90.0),
+      );
+
+      expect(
+        tester.getSize(find.widgetWithText(Container, '3.Who scream')),
+        const Size(400.0, 60.0),
+      );
+
+      expect(
+        tester.getSize(
+            find.widgetWithText(Container, '4.Revolution is coming...')),
+        const Size(400.0, 80.0),
+      );
+
+      expect(
+        tester.getSize(find.widgetWithText(Container, '5.Revolution, they...')),
+        const Size(400.0, 100.0),
+      );
+    });
+
+    testWidgets('the position of each child at TextDirection.ltr',
+        (WidgetTester tester) async {
+      await tester.pumpWidget(materialAppBoilerplate(
+        child: masonryGridViewWithChildrenBoilerplate(crossAxisCount: 2),
+        textDirection: TextDirection.ltr,
+      ));
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(
+            Container, "0.He'd have you all unravel at the")),
+        const Offset(0.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '1.Heed not the rabble')),
+        const Offset(400.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '2.Sound of screams but the')),
+        const Offset(0.0, 50.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3.Who scream')),
+        const Offset(400.0, 70.0),
+      );
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '4.Revolution is coming...')),
+        const Offset(400.0, 130.0),
+      );
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '5.Revolution, they...')),
+        const Offset(0.0, 140.0),
+      );
+    });
+
+    testWidgets('the position of each child at TextDirection.rtl',
+        (WidgetTester tester) async {
+      await tester.pumpWidget(
+        materialAppBoilerplate(
+            child: masonryGridViewWithChildrenBoilerplate(crossAxisCount: 2),
+            textDirection: TextDirection.rtl),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(
+            Container, "0.He'd have you all unravel at the")),
+        const Offset(400.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '1.Heed not the rabble')),
+        const Offset(0.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '2.Sound of screams but the')),
+        const Offset(400.0, 50.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3.Who scream')),
+        const Offset(0.0, 70.0),
+      );
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '4.Revolution is coming...')),
+        const Offset(0.0, 130.0),
+      );
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '5.Revolution, they...')),
+        const Offset(400.0, 140.0),
+      );
+    });
+
+    testWidgets('crossAxisCount change test', (WidgetTester tester) async {
+      int crossAxisCount = 2;
+      await tester.pumpWidget(
+        materialAppBoilerplate(
+            child: MasonryTestPage(
+              crossAxisCount: crossAxisCount,
+              setState: (_MasonryTestPageState state) {
+                state._crossAxisCount = crossAxisCount;
+              },
+            ),
+            textDirection: TextDirection.ltr),
+      );
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '2.Sound of screams but the')),
+        const Offset(0.0, 50.0),
+      );
+
+      crossAxisCount = 4;
+      await setStateBoilerplate(tester);
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '2.Sound of screams but the')),
+        const Offset(400.0, 0.0),
+      );
+    });
+
+    testWidgets('crossAxisSpacing change test', (WidgetTester tester) async {
+      double crossAxisSpacing = 10;
+      await tester.pumpWidget(
+        materialAppBoilerplate(
+            child: MasonryTestPage(
+              crossAxisSpacing: crossAxisSpacing,
+              crossAxisCount: 2,
+              setState: (_MasonryTestPageState state) {
+                state._crossAxisSpacing = crossAxisSpacing;
+              },
+            ),
+            textDirection: TextDirection.ltr),
+      );
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '2.Sound of screams but the')),
+        const Offset(0.0, 50.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3.Who scream')),
+        const Offset(405.0, 70.0),
+      );
+
+      crossAxisSpacing = 20;
+      await setStateBoilerplate(tester);
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '2.Sound of screams but the')),
+        const Offset(0.0, 50.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3.Who scream')),
+        const Offset(410.0, 70.0),
+      );
+    });
+
+    testWidgets('mainAxisSpacing change test', (WidgetTester tester) async {
+      double mainAxisSpacing = 10;
+      await tester.pumpWidget(
+        materialAppBoilerplate(
+            child: MasonryTestPage(
+              mainAxisSpacing: mainAxisSpacing,
+              crossAxisCount: 2,
+              setState: (_MasonryTestPageState state) {
+                state._mainAxisSpacing = mainAxisSpacing;
+              },
+            ),
+            textDirection: TextDirection.ltr),
+      );
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '2.Sound of screams but the')),
+        const Offset(0.0, 60.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3.Who scream')),
+        const Offset(400.0, 80.0),
+      );
+
+      mainAxisSpacing = 20;
+      await setStateBoilerplate(tester);
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '2.Sound of screams but the')),
+        const Offset(0.0, 70.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3.Who scream')),
+        const Offset(400.0, 90.0),
+      );
+    });
+
+    testWidgets('maxCrossAxisExtent change test', (WidgetTester tester) async {
+      double maxCrossAxisExtent = 400;
+      await tester.pumpWidget(
+        materialAppBoilerplate(
+            child: MasonryTestPage(
+              maxCrossAxisExtent: maxCrossAxisExtent,
+              setState: (_MasonryTestPageState state) {
+                state._maxCrossAxisExtent = maxCrossAxisExtent;
+              },
+            ),
+            textDirection: TextDirection.ltr),
+      );
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '2.Sound of screams but the')),
+        const Offset(0.0, 50.0),
+      );
+
+      maxCrossAxisExtent = 200;
+      await setStateBoilerplate(tester);
+
+      expect(
+        tester.getTopLeft(
+            find.widgetWithText(Container, '2.Sound of screams but the')),
+        const Offset(400.0, 0.0),
+      );
+    });
+
+    testWidgets('Vertical are primary by default', (WidgetTester tester) async {
+      final WaterfallFlow view = WaterfallFlow(
+        scrollDirection: Axis.vertical,
+        gridDelegate: const SliverWaterfallFlowDelegateWithFixedCrossAxisCount(
+            crossAxisCount: 3),
+      );
+      expect(view.primary, isTrue);
+    });
+
+    testWidgets('with controllers are non-primary by default',
+        (WidgetTester tester) async {
+      final WaterfallFlow view = WaterfallFlow(
+        controller: ScrollController(),
+        scrollDirection: Axis.vertical,
+        gridDelegate: const SliverWaterfallFlowDelegateWithFixedCrossAxisCount(
+            crossAxisCount: 3),
+      );
+      expect(view.primary, isFalse);
+    });
+
+    testWidgets('sets PrimaryScrollController when primary',
+        (WidgetTester tester) async {
+      final ScrollController primaryScrollController = ScrollController();
+      await tester.pumpWidget(
+        Directionality(
+          textDirection: TextDirection.ltr,
+          child: PrimaryScrollController(
+            controller: primaryScrollController,
+            child: WaterfallFlow(
+              primary: true,
+              gridDelegate:
+                  const SliverWaterfallFlowDelegateWithFixedCrossAxisCount(
+                      crossAxisCount: 3),
+            ),
+          ),
+        ),
+      );
+      final Scrollable scrollable = tester.widget(find.byType(Scrollable));
+      expect(scrollable.controller, primaryScrollController);
+    });
+
+    testWidgets('dismiss keyboard onDrag test', (WidgetTester tester) async {
+      final List<FocusNode> focusNodes =
+          List<FocusNode>.generate(50, (int i) => FocusNode());
+      await tester.pumpWidget(textFieldBoilerplate(
+        child: WaterfallFlow(
+          padding: const EdgeInsets.all(0),
+          gridDelegate:
+              const SliverWaterfallFlowDelegateWithFixedCrossAxisCount(
+            crossAxisCount: 2,
+          ),
+          keyboardDismissBehavior: ScrollViewKeyboardDismissBehavior.onDrag,
+          children: focusNodes.map((FocusNode focusNode) {
+            return Container(
+              height: 50,
+              color: Colors.green,
+              child: TextField(
+                  focusNode: focusNode,
+                  style: const TextStyle(
+                    fontSize: 24,
+                    fontWeight: FontWeight.bold,
+                  )),
+            );
+          }).toList(),
+        ),
+      ));
+
+      final Finder finder = find.byType(TextField).first;
+      final TextField textField = tester.widget(finder);
+      await tester.showKeyboard(finder);
+      expect(textField.focusNode.hasFocus, isTrue);
+
+      await tester.drag(finder, const Offset(0.0, -40.0));
+      await tester.pumpAndSettle();
+      expect(textField.focusNode.hasFocus, isFalse);
+    });
+
+    testWidgets('count dismiss keyboard onDrag test',
+        (WidgetTester tester) async {
+      final List<FocusNode> focusNodes =
+          List<FocusNode>.generate(50, (int i) => FocusNode());
+      await tester.pumpWidget(textFieldBoilerplate(
+        child: WaterfallFlow.count(
+          padding: const EdgeInsets.all(0),
+          crossAxisCount: 2,
+          keyboardDismissBehavior: ScrollViewKeyboardDismissBehavior.onDrag,
+          children: focusNodes.map((FocusNode focusNode) {
+            return Container(
+              height: 50,
+              color: Colors.green,
+              child: TextField(
+                  focusNode: focusNode,
+                  style: const TextStyle(
+                    fontSize: 24,
+                    fontWeight: FontWeight.bold,
+                  )),
+            );
+          }).toList(),
+        ),
+      ));
+
+      final Finder finder = find.byType(TextField).first;
+      final TextField textField = tester.widget(finder);
+      await tester.showKeyboard(finder);
+      expect(textField.focusNode.hasFocus, isTrue);
+
+      await tester.drag(finder, const Offset(0.0, -40.0));
+      await tester.pumpAndSettle();
+      expect(textField.focusNode.hasFocus, isFalse);
+    });
+
+    testWidgets('extent dismiss keyboard onDrag test',
+        (WidgetTester tester) async {
+      final List<FocusNode> focusNodes =
+          List<FocusNode>.generate(50, (int i) => FocusNode());
+      await tester.pumpWidget(textFieldBoilerplate(
+        child: WaterfallFlow.extent(
+          padding: const EdgeInsets.all(0),
+          maxCrossAxisExtent: 300,
+          keyboardDismissBehavior: ScrollViewKeyboardDismissBehavior.onDrag,
+          children: focusNodes.map((FocusNode focusNode) {
+            return Container(
+              height: 50,
+              color: Colors.green,
+              child: TextField(
+                  focusNode: focusNode,
+                  style: const TextStyle(
+                    fontSize: 24,
+                    fontWeight: FontWeight.bold,
+                  )),
+            );
+          }).toList(),
+        ),
+      ));
+
+      final Finder finder = find.byType(TextField).first;
+      final TextField textField = tester.widget(finder);
+      await tester.showKeyboard(finder);
+      expect(textField.focusNode.hasFocus, isTrue);
+
+      await tester.drag(finder, const Offset(0.0, -40.0));
+      await tester.pumpAndSettle();
+      expect(textField.focusNode.hasFocus, isFalse);
+    });
+
+    testWidgets('dismiss keyboard manual test', (WidgetTester tester) async {
+      final List<FocusNode> focusNodes =
+          List<FocusNode>.generate(50, (int i) => FocusNode());
+      await tester.pumpWidget(textFieldBoilerplate(
+        child: WaterfallFlow(
+          padding: const EdgeInsets.all(0),
+          gridDelegate:
+              const SliverWaterfallFlowDelegateWithFixedCrossAxisCount(
+            crossAxisCount: 2,
+          ),
+          keyboardDismissBehavior: ScrollViewKeyboardDismissBehavior.manual,
+          children: focusNodes.map((FocusNode focusNode) {
+            return Container(
+              height: 50,
+              color: Colors.green,
+              child: TextField(
+                  focusNode: focusNode,
+                  style: const TextStyle(
+                    fontSize: 24,
+                    fontWeight: FontWeight.bold,
+                  )),
+            );
+          }).toList(),
+        ),
+      ));
+
+      final Finder finder = find.byType(TextField).first;
+      final TextField textField = tester.widget(finder);
+      await tester.showKeyboard(finder);
+      expect(textField.focusNode.hasFocus, isTrue);
+
+      await tester.drag(finder, const Offset(0.0, -40.0));
+      await tester.pumpAndSettle();
+      expect(textField.focusNode.hasFocus, isTrue);
+    });
+
+    testWidgets('count dismiss keyboard manual test',
+        (WidgetTester tester) async {
+      final List<FocusNode> focusNodes =
+          List<FocusNode>.generate(50, (int i) => FocusNode());
+      await tester.pumpWidget(textFieldBoilerplate(
+        child: WaterfallFlow.count(
+          padding: const EdgeInsets.all(0),
+          crossAxisCount: 2,
+          keyboardDismissBehavior: ScrollViewKeyboardDismissBehavior.manual,
+          children: focusNodes.map((FocusNode focusNode) {
+            return Container(
+              height: 50,
+              color: Colors.green,
+              child: TextField(
+                  focusNode: focusNode,
+                  style: const TextStyle(
+                    fontSize: 24,
+                    fontWeight: FontWeight.bold,
+                  )),
+            );
+          }).toList(),
+        ),
+      ));
+
+      final Finder finder = find.byType(TextField).first;
+      final TextField textField = tester.widget(finder);
+      await tester.showKeyboard(finder);
+      expect(textField.focusNode.hasFocus, isTrue);
+
+      await tester.drag(finder, const Offset(0.0, -40.0));
+      await tester.pumpAndSettle();
+      expect(textField.focusNode.hasFocus, isTrue);
+    });
+
+    testWidgets('extend dismiss keyboard manual test',
+        (WidgetTester tester) async {
+      final List<FocusNode> focusNodes =
+          List<FocusNode>.generate(50, (int i) => FocusNode());
+      await tester.pumpWidget(textFieldBoilerplate(
+        child: WaterfallFlow.extent(
+          padding: const EdgeInsets.all(0),
+          maxCrossAxisExtent: 300,
+          keyboardDismissBehavior: ScrollViewKeyboardDismissBehavior.manual,
+          children: focusNodes.map((FocusNode focusNode) {
+            return Container(
+              height: 50,
+              color: Colors.green,
+              child: TextField(
+                  focusNode: focusNode,
+                  style: const TextStyle(
+                    fontSize: 24,
+                    fontWeight: FontWeight.bold,
+                  )),
+            );
+          }).toList(),
+        ),
+      ));
+
+      final Finder finder = find.byType(TextField).first;
+      final TextField textField = tester.widget(finder);
+      await tester.showKeyboard(finder);
+      expect(textField.focusNode.hasFocus, isTrue);
+
+      await tester.drag(finder, const Offset(0.0, -40.0));
+      await tester.pumpAndSettle();
+      expect(textField.focusNode.hasFocus, isTrue);
+    });
+
+    testWidgets('itemCount change test', (WidgetTester tester) async {
+      final ScrollController controller = ScrollController();
+      int itemCount = 100;
+      await tester.pumpWidget(
+        materialAppBoilerplate(
+            child: MasonryTestPage(
+          controller: controller,
+          crossAxisCount: 4,
+          items: List<int>.generate(itemCount, (int index) => index),
+          setState: (_MasonryTestPageState state) {
+            state._items = List<int>.generate(itemCount, (int index) => index);
+          },
+          builder: true,
+        )),
+      );
+      expect(find.widgetWithText(Container, '0'), findsOneWidget);
+      controller.jumpTo(10000);
+      await tester.pumpAndSettle();
+
+      itemCount = 0;
+      await setStateBoilerplate(tester);
+
+      expect(find.widgetWithText(Container, '0'), findsNothing);
+      expect(controller.offset, 0.0);
+
+      itemCount = 100;
+      await setStateBoilerplate(tester);
+
+      expect(find.widgetWithText(Container, '3'), findsOneWidget);
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '0')),
+        const Offset(0.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '1')),
+        const Offset(200.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '2')),
+        const Offset(400.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3')),
+        const Offset(600.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '4')),
+        const Offset(0.0, 100.0),
+      );
+    });
+
+    testWidgets('items removeRange test', (WidgetTester tester) async {
+      final ScrollController controller = ScrollController();
+      int start;
+      int end;
+      await tester.pumpWidget(
+        materialAppBoilerplate(
+            child: MasonryTestPage(
+          controller: controller,
+          crossAxisCount: 4,
+          items: List<int>.generate(100, (int index) => index),
+          setState: (_MasonryTestPageState state) {
+            state._items.removeRange(start, end);
+          },
+          builder: true,
+        )),
+      );
+      expect(find.widgetWithText(Container, '0'), findsOneWidget);
+      controller.jumpTo(10000);
+      await tester.pumpAndSettle();
+
+      start = 40;
+      end = 60;
+      await setStateBoilerplate(tester);
+      controller.jumpTo(0);
+      await tester.pumpAndSettle();
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '0')),
+        const Offset(0.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '1')),
+        const Offset(200.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '2')),
+        const Offset(400.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3')),
+        const Offset(600.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '4')),
+        const Offset(0.0, 100.0),
+      );
+    });
+
+    // code coverage: [RenderSliverMasonryGrid]
+    // if (data.layoutOffset < -precisionErrorTolerance)
+    testWidgets('the child who out of viewport change big test',
+        (WidgetTester tester) async {
+      final ScrollController controller = ScrollController();
+      double size;
+      await tester.pumpWidget(
+        materialAppBoilerplate(
+            child: MasonryTestPage(
+          controller: controller,
+          crossAxisCount: 4,
+          items: List<int>.generate(100, (int index) => index),
+          sizeBuilder: (int index) {
+            if (index == 1 && size != null) {
+              return size;
+            }
+            return null;
+          },
+          builder: true,
+        )),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '0')),
+        const Offset(0.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '1')),
+        const Offset(200.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '2')),
+        const Offset(400.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3')),
+        const Offset(600.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '4')),
+        const Offset(0.0, 100.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '5')),
+        const Offset(0.0, 200.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '6')),
+        const Offset(200.0, 200.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '7')),
+        const Offset(400.0, 300.0),
+      );
+
+      controller.jumpTo(10000);
+      await tester.pumpAndSettle();
+      expect(find.widgetWithText(Container, '0'), findsNothing);
+
+      // change child size from 200 to 500.
+      size = 500;
+      await setStateBoilerplate(tester);
+      controller.jumpTo(0);
+      await tester.pumpAndSettle();
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '0')),
+        const Offset(0.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '1')),
+        const Offset(200.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '2')),
+        const Offset(400.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3')),
+        const Offset(600.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '4')),
+        const Offset(0.0, 100.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '5')),
+        const Offset(0.0, 200.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '6')),
+        const Offset(400.0, 300.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '7')),
+        const Offset(0.0, 400.0),
+      );
+    });
+
+    // code coverage: [RenderSliverMasonryGrid]
+    // if (earliestUsefulChild == null) {
+    testWidgets('the child who out of viewport change small sroll into 0 test',
+        (WidgetTester tester) async {
+      final ScrollController controller = ScrollController();
+      double size;
+      await tester.pumpWidget(
+        materialAppBoilerplate(
+            child: MasonryTestPage(
+          controller: controller,
+          crossAxisCount: 4,
+          items: List<int>.generate(100, (int index) => index),
+          sizeBuilder: (int index) {
+            if (index == 0 && size != null) {
+              return size;
+            }
+            return null;
+          },
+          builder: true,
+        )),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '0')),
+        const Offset(0.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '1')),
+        const Offset(200.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '2')),
+        const Offset(400.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3')),
+        const Offset(600.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '4')),
+        const Offset(0.0, 100.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '5')),
+        const Offset(0.0, 200.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '6')),
+        const Offset(200.0, 200.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '7')),
+        const Offset(400.0, 300.0),
+      );
+
+      controller.jumpTo(10000);
+      await tester.pumpAndSettle();
+      expect(find.widgetWithText(Container, '0'), findsNothing);
+
+      // change child size from 100 to 30.
+      size = 30;
+      await setStateBoilerplate(tester);
+      controller.jumpTo(0);
+      await tester.pumpAndSettle();
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '0')),
+        const Offset(0.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '1')),
+        const Offset(200.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '2')),
+        const Offset(400.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3')),
+        const Offset(600.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '4')),
+        const Offset(0.0, 30.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '5')),
+        const Offset(0.0, 130.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '6')),
+        const Offset(200.0, 200.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '7')),
+        const Offset(400.0, 300.0),
+      );
+    });
+
+    // code coverage: [RenderSliverMasonryGrid]
+    // if (earliestUsefulChild == null) {
+    testWidgets(
+        'the child who out of viewport change small sroll into 100 test',
+        (WidgetTester tester) async {
+      final ScrollController controller = ScrollController();
+      double size;
+      await tester.pumpWidget(
+        materialAppBoilerplate(
+            child: MasonryTestPage(
+          controller: controller,
+          crossAxisCount: 4,
+          items: List<int>.generate(100, (int index) => index),
+          sizeBuilder: (int index) {
+            if (index == 1 && size != null) {
+              return size;
+            }
+            return null;
+          },
+          builder: true,
+        )),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '0')),
+        const Offset(0.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '1')),
+        const Offset(200.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '2')),
+        const Offset(400.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3')),
+        const Offset(600.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '4')),
+        const Offset(0.0, 100.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '5')),
+        const Offset(0.0, 200.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '6')),
+        const Offset(200.0, 200.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '7')),
+        const Offset(400.0, 300.0),
+      );
+
+      controller.jumpTo(10000);
+      await tester.pumpAndSettle();
+      expect(find.widgetWithText(Container, '0'), findsNothing);
+
+      // change child size from 100 to 30.
+      size = 30;
+      await setStateBoilerplate(tester);
+      controller.jumpTo(100);
+      await tester.pumpAndSettle();
+
+      expect(find.widgetWithText(Container, '0'), findsNothing);
+
+      expect(find.widgetWithText(Container, '1'), findsNothing);
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '2')),
+        const Offset(400.0, -100.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3')),
+        const Offset(600.0, -100.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '4')),
+        const Offset(200.0, -70.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '5')),
+        const Offset(0.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '6')),
+        const Offset(200.0, 30.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '7')),
+        const Offset(0.0, 200.0),
+      );
+    });
+
+    // code coverage: [RenderSliverMasonryGrid]
+    // if (data.layoutOffset < -precisionErrorTolerance)
+    testWidgets('insert child out of viewport test',
+        (WidgetTester tester) async {
+      final ScrollController controller = ScrollController();
+      double size;
+      await tester.pumpWidget(
+        materialAppBoilerplate(
+            child: MasonryTestPage(
+          controller: controller,
+          crossAxisCount: 4,
+          items: List<int>.generate(100, (int index) => index),
+          sizeBuilder: (int index) {
+            if (index == 0 && size != null) {
+              return size;
+            }
+            return null;
+          },
+          setState: (_MasonryTestPageState state) {
+            state._items.insert(0, 999);
+          },
+          builder: true,
+        )),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '0')),
+        const Offset(0.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '1')),
+        const Offset(200.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '2')),
+        const Offset(400.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3')),
+        const Offset(600.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '4')),
+        const Offset(0.0, 100.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '5')),
+        const Offset(0.0, 200.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '6')),
+        const Offset(200.0, 200.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '7')),
+        const Offset(400.0, 300.0),
+      );
+
+      controller.jumpTo(10000);
+      await tester.pumpAndSettle();
+      expect(find.widgetWithText(Container, '0'), findsNothing);
+
+      // insert 999 into 0 index with size 500.0.
+      size = 500;
+      await setStateBoilerplate(tester);
+      controller.jumpTo(0);
+      await tester.pumpAndSettle();
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '999')),
+        const Offset(0.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '0')),
+        const Offset(200.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '1')),
+        const Offset(400.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '2')),
+        const Offset(600.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3')),
+        const Offset(200.0, 200.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '4')),
+        const Offset(200.0, 300.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '5')),
+        const Offset(400.0, 300.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '7')),
+        const Offset(0.0, 500.0),
+      );
+    });
+
+    testWidgets('remove child out of viewport test',
+        (WidgetTester tester) async {
+      final ScrollController controller = ScrollController();
+      int removeIndex;
+      await tester.pumpWidget(
+        materialAppBoilerplate(
+            child: MasonryTestPage(
+          controller: controller,
+          crossAxisCount: 4,
+          items: List<int>.generate(100, (int index) => index),
+          sizeBuilder: (int index) {
+            if (removeIndex != null && index >= removeIndex) {
+              return (((index + 1) % 4) + 1) * 100.0;
+            }
+            return null;
+          },
+          setState: (_MasonryTestPageState state) {
+            state._items.remove(removeIndex);
+          },
+          builder: true,
+        )),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '0')),
+        const Offset(0.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '1')),
+        const Offset(200.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '2')),
+        const Offset(400.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '3')),
+        const Offset(600.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '4')),
+        const Offset(0.0, 100.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '5')),
+        const Offset(0.0, 200.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '6')),
+        const Offset(200.0, 200.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '7')),
+        const Offset(400.0, 300.0),
+      );
+
+      controller.jumpTo(10000);
+      await tester.pumpAndSettle();
+      expect(find.widgetWithText(Container, '0'), findsNothing);
+
+      // remove index 3.
+      removeIndex = 3;
+      await setStateBoilerplate(tester);
+      controller.jumpTo(0);
+      await tester.pumpAndSettle();
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '0')),
+        const Offset(0.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '1')),
+        const Offset(200.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '2')),
+        const Offset(400.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '4')),
+        const Offset(600.0, 0.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '5')),
+        const Offset(0.0, 100.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '6')),
+        const Offset(600.0, 100.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '7')),
+        const Offset(200.0, 200.0),
+      );
+
+      expect(
+        tester.getTopLeft(find.widgetWithText(Container, '8')),
+        const Offset(0.0, 300.0),
+      );
+    });
+  });
+}
+
+Widget masonryGridViewWithChildrenBoilerplate({
+  int crossAxisCount = 2,
+  double crossAxisSpacing = 0.0,
+  double mainAxisSpacing = 0.0,
+  double maxCrossAxisExtent,
+  ScrollController controller,
+}) {
+  final List<Widget> children = <Widget>[
+    Container(
+      padding: const EdgeInsets.all(8),
+      child: const Text("0.He'd have you all unravel at the"),
+      color: Colors.teal[100],
+      height: 50.0,
+    ),
+    Container(
+      padding: const EdgeInsets.all(8),
+      child: const Text('1.Heed not the rabble'),
+      color: Colors.teal[200],
+      height: 70.0,
+    ),
+    Container(
+      padding: const EdgeInsets.all(8),
+      child: const Text('2.Sound of screams but the'),
+      color: Colors.teal[300],
+      height: 90.0,
+    ),
+    Container(
+      padding: const EdgeInsets.all(8),
+      child: const Text('3.Who scream'),
+      color: Colors.teal[400],
+      height: 60.0,
+    ),
+    Container(
+      padding: const EdgeInsets.all(8),
+      child: const Text('4.Revolution is coming...'),
+      color: Colors.teal[500],
+      height: 80.0,
+    ),
+    Container(
+      padding: const EdgeInsets.all(8),
+      child: const Text('5.Revolution, they...'),
+      color: Colors.teal[600],
+      height: 100.0,
+    ),
+  ];
+
+  if (maxCrossAxisExtent != null) {
+    return WaterfallFlow.extent(
+      maxCrossAxisExtent: maxCrossAxisExtent,
+      crossAxisSpacing: crossAxisSpacing,
+      mainAxisSpacing: mainAxisSpacing,
+      children: children,
+      controller: controller,
+    );
+  }
+
+  return WaterfallFlow.count(
+    crossAxisCount: crossAxisCount,
+    crossAxisSpacing: crossAxisSpacing,
+    mainAxisSpacing: mainAxisSpacing,
+    children: children,
+    controller: controller,
+  );
+}
+
+Widget masonryGridViewBuilderBoilerplate({
+  int crossAxisCount = 4,
+  double crossAxisSpacing = 0.0,
+  double mainAxisSpacing = 0.0,
+  double maxCrossAxisExtent,
+  ScrollController controller,
+  List<int> items,
+  double Function(int index) sizeBuilder,
+}) {
+  final SliverWaterfallFlowDelegate delegate = maxCrossAxisExtent != null
+      ? SliverWaterfallFlowDelegateWithMaxCrossAxisExtent(
+          maxCrossAxisExtent: maxCrossAxisExtent,
+          mainAxisSpacing: mainAxisSpacing,
+          crossAxisSpacing: crossAxisSpacing,
+        )
+      : SliverWaterfallFlowDelegateWithFixedCrossAxisCount(
+          crossAxisCount: crossAxisCount,
+          mainAxisSpacing: mainAxisSpacing,
+          crossAxisSpacing: crossAxisSpacing,
+        );
+
+  return WaterfallFlow.builder(
+    gridDelegate: delegate,
+    itemBuilder: (BuildContext context, int index) {
+      return Container(
+        child: Text(
+          '${items[index]}',
+        ),
+        height:
+            sizeBuilder?.call(index) ?? ((index % crossAxisCount) + 1) * 100.0,
+      );
+    },
+    itemCount: items.length,
+    controller: controller,
+  );
+}
+
+Widget materialAppBoilerplate(
+    {Widget child, TextDirection textDirection = TextDirection.ltr}) {
+  return MaterialApp(
+    home: Directionality(
+      textDirection: textDirection,
+      child: MediaQuery(
+        data: const MediaQueryData(size: Size(800.0, 600.0)),
+        child: Material(
+          child: child,
+        ),
+      ),
+    ),
+  );
+}
+
+Widget textFieldBoilerplate({Widget child}) {
+  return MaterialApp(
+    home: Localizations(
+      locale: const Locale('en', 'US'),
+      delegates: <LocalizationsDelegate<dynamic>>[
+        WidgetsLocalizationsDelegate(),
+        MaterialLocalizationsDelegate(),
+      ],
+      child: Directionality(
+        textDirection: TextDirection.ltr,
+        child: MediaQuery(
+          data: const MediaQueryData(size: Size(800.0, 600.0)),
+          child: Center(
+            child: Material(
+              child: child,
+            ),
+          ),
+        ),
+      ),
+    ),
+  );
+}
+
+class MasonryTestPage extends StatefulWidget {
+  const MasonryTestPage({
+    this.crossAxisCount = 4,
+    this.mainAxisSpacing = 0.0,
+    this.crossAxisSpacing = 0.0,
+    this.textDirection = TextDirection.ltr,
+    this.maxCrossAxisExtent,
+    this.items,
+    this.controller,
+    this.setState,
+    this.builder = false,
+    this.sizeBuilder,
+  });
+  final int crossAxisCount;
+  final double mainAxisSpacing;
+  final double crossAxisSpacing;
+  final TextDirection textDirection;
+  final double maxCrossAxisExtent;
+  final List<int> items;
+  final ScrollController controller;
+  final void Function(_MasonryTestPageState setState) setState;
+  final bool builder;
+  final double Function(int index) sizeBuilder;
+  @override
+  _MasonryTestPageState createState() => _MasonryTestPageState();
+}
+
+class _MasonryTestPageState extends State<MasonryTestPage> {
+  int _crossAxisCount;
+  double _crossAxisSpacing;
+  double _mainAxisSpacing;
+  TextDirection _textDirection;
+  double _maxCrossAxisExtent;
+  List<int> _items;
+  @override
+  void initState() {
+    _crossAxisCount = widget.crossAxisCount;
+    _mainAxisSpacing = widget.mainAxisSpacing;
+    _crossAxisSpacing = widget.crossAxisSpacing;
+    _textDirection = widget.textDirection;
+    _maxCrossAxisExtent = widget.maxCrossAxisExtent;
+    _items = widget.items;
+    super.initState();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      body: Directionality(
+        textDirection: _textDirection,
+        child: widget.builder
+            ? masonryGridViewBuilderBoilerplate(
+                crossAxisCount: _crossAxisCount,
+                mainAxisSpacing: _mainAxisSpacing,
+                crossAxisSpacing: _crossAxisSpacing,
+                maxCrossAxisExtent: _maxCrossAxisExtent,
+                controller: widget.controller,
+                items: _items,
+                sizeBuilder: widget.sizeBuilder,
+              )
+            : masonryGridViewWithChildrenBoilerplate(
+                crossAxisCount: _crossAxisCount,
+                mainAxisSpacing: _mainAxisSpacing,
+                crossAxisSpacing: _crossAxisSpacing,
+                maxCrossAxisExtent: _maxCrossAxisExtent,
+                controller: widget.controller,
+              ),
+      ),
+      floatingActionButton: FloatingActionButton(
+        onPressed: () {
+          setState(() {
+            widget.setState?.call(this);
+          });
+        },
+        child: const Icon(Icons.add),
+      ),
+    );
+  }
+}
+
+Future<void> setStateBoilerplate(WidgetTester tester) async {
+  await tester.tap(find.byType(FloatingActionButton));
+  await tester.pumpAndSettle();
+}
+
+class MaterialLocalizationsDelegate
+    extends LocalizationsDelegate<MaterialLocalizations> {
+  @override
+  bool isSupported(Locale locale) => true;
+
+  @override
+  Future<MaterialLocalizations> load(Locale locale) =>
+      DefaultMaterialLocalizations.load(locale);
+
+  @override
+  bool shouldReload(MaterialLocalizationsDelegate old) => false;
+}
+
+class WidgetsLocalizationsDelegate
+    extends LocalizationsDelegate<WidgetsLocalizations> {
+  @override
+  bool isSupported(Locale locale) => true;
+
+  @override
+  Future<WidgetsLocalizations> load(Locale locale) =>
+      DefaultWidgetsLocalizations.load(locale);
+
+  @override
+  bool shouldReload(WidgetsLocalizationsDelegate old) => false;
+}