I am working on a Flutter app and need to pop the screen. I tried initState() method but no luck. initState() gets called when I open a class for the first time.

Do we have an equivalent of Android onResume() method in Flutter?

Any ideas?


Solution 1: diegoveloper

You can use the WidgetsBindingObserver and check the AppLifeCycleState like this example:

class YourWidgetState extends State<YourWidget> 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) {
       //do your stuff
    }
  }
}

Take in mind that It will called every time you open the app or go the background and return to the app. (if your widget is active)

If you just want a listener when your Widget is loaded for first time, you can listen using addPostFrameCallback, like this example:

class YourWidgetState extends State<YourWidget> {

  _onLayoutDone(_) {
    //do your stuff
  }

  @override
  void initState() {
    WidgetsBinding.instance?.addPostFrameCallback(_onLayoutDone);
    super.initState();
  } 

}

Info : https://docs.flutter.io/flutter/widgets/WidgetsBindingObserver-class.html

Update: Null safety compliance


Solution 2: Arto Bendiken

You can accomplish this by registering a didChangeAppLifecycleState observer:

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

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

  @override
  void didChangeAppLifecycleState(final AppLifecycleState state) {
    if (state == AppLifecycleState.resumed) {
      setState(() {
        // ...your code goes here...
      });
    }
  }

  @override
  Widget build(final BuildContext context) {
    // ...your code goes here...
  }
}

See WidgetsBindingObserver for more information.


Solution 3: Álvaro Agüero

If you go to another page, then is called when you comeback

Navigator.push(
  context,
  MaterialPageRoute(
    builder: (context) => SecondPage(),
  ),
).then((value) {
  _refreshFirstPage();
});


Solution 4: 朱相卿

Use focus_detector more information can see visibility_detector

Get notified every time your widget appears or disappears from the screen.

Similar to onResume()/onPause() on Android and viewDidAppear()/viewDidDisappear() on iOS.

Focus Detector fires callbacks for you whenever something happens to take or give your widget focus. Such an event might be, for instance, the user:

Navigating to/from another screen;

Turning the device’s screen on/off while your widget is visible;

Switching to/from another app while your widget is visible;

Scrolling your widget in/out the screen;

@override
Widget build(BuildContext context) =>
    FocusDetector(
      onFocusLost: () {
        logger.i(
          'Focus Lost.'
          '\nTriggered when either [onVisibilityLost] or [onForegroundLost] '
          'is called.'
          '\nEquivalent to onPause() on Android or viewDidDisappear() on iOS.',
        );
      },
      onFocusGained: () {
        logger.i(
          'Focus Gained.'
          '\nTriggered when either [onVisibilityGained] or [onForegroundGained] '
          'is called.'
          '\nEquivalent to onResume() on Android or viewDidAppear() on iOS.',
        );
      },
      onVisibilityLost: () {
        logger.i(
          'Visibility Lost.'
          '\nIt means the widget is no longer visible within your app.',
        );
      },
      onVisibilityGained: () {
        logger.i(
          'Visibility Gained.'
          '\nIt means the widget is now visible within your app.',
        );
      },
      onForegroundLost: () {
        logger.i(
          'Foreground Lost.'
          '\nIt means, for example, that the user sent your app to the background by opening '
          'another app or turned off the device\'s screen while your '
          'widget was visible.',
        );
      },
      onForegroundGained: () {
        logger.i(
          'Foreground Gained.'
          '\nIt means, for example, that the user switched back to your app or turned the '
          'device\'s screen back on while your widget was visible.',
        );
      },
      child: Container(),
    );