Flutter A value of type 'Future<dynamic>' can't be returned from the method '_onBackPress' because it has a return type of 'Future<bool>'

Issue

i am working on back button in my app but i face this issue in flutter
Thank so much in advanced
i am doing this before with this function but now it’s not working
i think because of null safty
sorry for my bad english
screenshot

here is my flutter doctor

Doctor summary (to see all details, run flutter doctor -v):
[√] Flutter (Channel stable, 2.2.3, on Microsoft Windows [Version 10.0.19043.1110], locale en-US)
[√] Android toolchain - develop for Android devices (Android SDK version 30.0.3)
[√] Chrome - develop for the web
[√] Android Studio (version 4.1.0)
[√] VS Code (version 1.58.2)
[√] Connected device (3 available)

• No issues found!

here is my build method and Future function

Future<bool> _onBackPress() {
    return showDialog(
      context: context,
      builder: (BuildContext context) {
        return AlertDialog(
          content: Text('Exit From The App'),
          actions: [
            TextButton(
              onPressed: () {
                Navigator.of(context).pop(false);
              },
              child: Text('No'),
            ),
            TextButton(
              onPressed: () {
                Navigator.of(context).pop(true);
              },
              child: Text('Yes'),
            ),
          ],
        );
      },
    );
  }

  @override
  Widget build(BuildContext context) {
    return WillPopScope(
      onWillPop: _onBackPress,
      child: Scaffold(
        appBar: AppBar(
          automaticallyImplyLeading: false,
          brightness: Brightness.dark,
          title: Text('Internet Availability Checker'),
        ),
      ),
    );
  }

Solution

In your _onBackPress() function you are not returning a bool. It should be rewritten like this:

Future<bool> _onBackPress() async {
  bool goBack = false;
  await showDialog(
    context: context,
    builder: (BuildContext context) {
      return AlertDialog(
        content: Text('Exit From The App'),
        actions: [
          TextButton(
            onPressed: () {
              goBack = false;
              Navigator.pop(context);
            },
            child: Text('No'),
          ),
          TextButton(
            onPressed: () {
              goBack = true;
              Navigator.pop(context);
            },
            child: Text('Yes'),
          ),
        ],
      );
    },
  );
  return goBack;
}

Answered By – PatrickMahomes

Answer Checked By – Cary Denson (FlutterFixes Admin)