Flutter Excpetion using Provider to change Variable from child to parent.

[Michele-x98]

Describe the bug
When i binding a Boolean variable in ModalProgressHUD to a watch() provider, and I try to change it in another Widget, the child widget are disposed and I can't access to context, for example to navigate to a another page.
To Reproduce

class Provider with ChangeNotifier {
  bool _inAsync = false;

  bool get inAsync => _inAsync;

  void setInAsync(bool flag) {
    this._inAsync = flag;
    notifyListeners();
  }
}

 void main() async {
   runApp(App());
 }

class App extends StatefulWidget {
  @override
  _AppState createState() => _AppState();
}

class _AppState extends State<App> {
  @override
  void initState() {
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return MultiProvider(
      providers: [
        ChangeNotifierProvider(
          create: (context) => CartProvider(),
        )
      ],
      child: MaterialApp(
        home: HomePage(),
      ),
    );
  }
}

class _FirstStatefulWidgetState extends State<FirstStatefulWidget> {
  late CartProvider cartProvider = context.read<CartProvider>();

  Future doSomething() async {
    cartProvider.setInAsync(true);
    await Future.delayed(
      Duration(seconds: 2),
      () => {
        cartProvider.setInAsync(false),
        Navigator.push(
          context,
          MaterialPageRoute(
            builder: (context) => SecondPage(),
          ),
        )
      },
    );
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      child: ElevatedButton(
        child: Text('do call'),
        onPressed: doSomething,
      ),
    );
  }
}

class SecondStatefulWidget extends StatefulWidget {
  SecondStatefulWidget({Key? key}) : super(key: key);

  @override
  _SecondStatefulWidgetState createState() => _SecondStatefulWidgetState();
}

class _SecondStatefulWidgetState extends State<SecondStatefulWidget> {
  late CartProvider cartProvider = context.read<CartProvider>();

  void goToAnotherPageAfterCall() async {
    try {
      cartProvider.setInAsync(true);
      Future.delayed(
        Duration(seconds: 2),
        () => {
          cartProvider.setInAsync(false),
          Navigator.push(
            context,
            new MaterialPageRoute(
              builder: (context) => SecondPage(),
            ),
          )
        },
      );
    } on Exception catch (e) {
      cartProvider.setInAsync(false);
    }
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      child: ElevatedButton(
        child: Text('goToAnotherPage'),
        onPressed: goToAnotherPageAfterCall,
      ),
    );
  }
}

Expected behavior
The expected behaviour is that when I do an async call, via provider I can change the "inAsync" variable to true, and the circular progress indicator appear, then, when the future complete, I want to set inAsync to false, and after the progress disappear, navigate to a new page or do somethings that require the context.

[rrousselGit]

Hello

Could you reformulate the bug description/expected behaviour? I do not understand what the bug is.

[Michele-x98]

https://stackoverflow.com/questions/68628890/flutter-nullsafety-cannot-push-page-after-showing-and-change-modalprogresshud

I opened a question on stack overflow where I explain the problem. Maybe it's clearer and you can also see the exception logs