应用程序终止时如何打开对话框 - Flutter？

Question

当应用程序终止时，我需要打开对话框。 我在WidgetsBindingObserver的帮助下检查了应用程序的生命周期

@override
  void initState() {
    WidgetsBinding.instance.addObserver(this);
    super.initState();
  }

  @override
  void dispose() {
    WidgetsBinding.instance.removeObserver(this);
    super.dispose();
  }

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    if(state == AppLifecycleState.resumed){
      print('app is resumed');
    } else if(state == AppLifecycleState.inactive){
      print('app is inactive');
    } else if(state == AppLifecycleState.paused){
      print('app is paused');
    } else if(state == AppLifecycleState.detached) {
      print('app is detached');
      if(state == AppLifecycleState.resumed){
        print('app is resumed');
      }
      SchedulerBinding.instance.addPostFrameCallback((_) => CustomDialogBox() );
    }
  }

就像当应用程序 state 变为AppLifecycleState.detached时，应用程序被终止，而当应用程序 state 再次变为AppLifecycleState.resumed以显示对话框，但无法这样做。

有没有不同的方法来实现这一目标？

编辑这是应用程序终止时显示的屏幕

class HomeScreen extends StatefulWidget {
  @override
  _HomeScreenState createState() => _HomeScreenState();
}

class _HomeScreenState extends State<HomeScreen> with WidgetsBindingObserver {
   @override
  void initState() {
    WidgetsBinding.instance.addObserver(this);
    super.initState();
  }

  @override
  void dispose() {
    WidgetsBinding.instance.removeObserver(this);
    super.dispose();
  }

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    if(state == AppLifecycleState.resumed){
      print('app is resumed');
    } else if(state == AppLifecycleState.inactive){
      print('app is inactive');
    } else if(state == AppLifecycleState.paused){
      print('app is paused');
    } else if(state == AppLifecycleState.detached) {
      print('app is detached');
      showDialog(context: context, builder: (BuildContext context){
        return AlertDialog(
          title: Text('AlertDialog Title'),
          content: SingleChildScrollView(
            child: ListBody(
              children: <Widget>[
                Text('This is a demo alert dialog.'),
                Text('Would you like to approve of this message?'),
              ],
            ),
          ),
        );
      });
      // SchedulerBinding.instance.addPostFrameCallback((_) => CustomDialogBox() );
    }
  }

   @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar()
    )
  }
}

日志猫

I/flutter ( 8810): app is inactive
I/flutter ( 8810): app is paused
I/flutter ( 8810): app is resumed
D/DecorView( 8810): onWindowFocusChangedFromViewRoot hasFocus: true, DecorView@bc1e6a7[MainActivity]
I/flutter ( 8810): app is inactive
I/flutter ( 8810): app is paused
I/flutter ( 8810): app is detached
D/OnePlusJankManager( 8810):  Chor uploadMDM JANK_TYPE_ONCE mViewTitle = com.example.postman/com.example.postman.MainActivity--- jank level = 1

Answer 1

当您恢复应用程序时，将showDialog调用移至。 在应用程序已分离后，flutter 可能无法构建对话框。

@override
void didChangeAppLifecycleState(AppLifecycleState state) {
  if(state == AppLifecycleState.resumed){
    print('app is resumed');
    showDialog(context: context, builder: (BuildContext context){
      return AlertDialog(
        title: Text('AlertDialog Title'),
        content: SingleChildScrollView(
          child: ListBody(
            children: <Widget>[
              Text('This is a demo alert dialog.'),
              Text('Would you like to approve of this message?'),
            ],
          ),
        ),
      );
    });
  } else if(state == AppLifecycleState.inactive){
    print('app is inactive');
  } else if(state == AppLifecycleState.paused){
    print('app is paused');
  } else if(state == AppLifecycleState.detached) {
    print('app is detached');
  }
}