Add default activity

android/src/main/AndroidManifest.xml

 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
   package="com.idlefish.flutterboost">
+
+    <application>
+        <activity android:name="com.idlefish.flutterboost.containers.BoostFlutterDefaultActivity" />
+    </application>
+
 </manifest>

android/src/main/java/com/idlefish/flutterboost/containers/BoostFlutterDefaultActivity.java

+package com.idlefish.flutterboost.containers;
+
+import android.app.Activity;
+import android.content.Context;
+import android.content.Intent;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class BoostFlutterDefaultActivity extends BoostFlutterActivity {
+
+    @Override
+    public String getContainerUrl() {
+        return getIntent().getStringExtra("url");
+    }
+
+    @Override
+    public Map getContainerUrlParams() {
+        return (Map)(getIntent().getSerializableExtra("params"));
+    }
+
+    private static Intent intent(Context context, String url, HashMap<String, Object> params) {
+        final Intent intent = new Intent(context, BoostFlutterDefaultActivity.class);
+        intent.putExtra("url", url);
+        intent.putExtra("params", params);
+        return intent;
+    }
+
+    public static void open(Context context, String url, HashMap<String, Object> params) {
+        context.startActivity(intent(context, url, params));
+    }
+
+    public static void open(Activity activity, String url, HashMap<String, Object> params, int requestCode) {
+        activity.startActivityForResult(intent(activity, url, params), requestCode);
+    }
+}
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