增加回到前台事件

ios/Classes/Boost/FlutterBoostPlugin.m

@@ -42,6 +42,7 @@
     FlutterBoostPlugin* instance = [self.class sharedInstance];
     instance.methodChannel = channel;
     [registrar addMethodCallDelegate:instance channel:channel];
+    [registrar addApplicationDelegate:instance];
 }
 
 - (void)handleMethodCall:(FlutterMethodCall*)call result:(FlutterResult)result {
@@ -215,4 +216,9 @@
     self.methodChannel = nil;
     self.application = nil;
 }
+
+#pragma mark appDelegate
+- (void)applicationDidBecomeActive:(UIApplication *)application{
+    [self sendEvent:@"applicationDidBecomeActive" arguments:@{@"status":@"applicationDidBecomeActive"}];
+}
 @end