Flutter Provider - Widget not subscribing to updates

Question

I want my widget to listen to updates to the provided FormViewModel , a ChangNotifier . In the widget, the notifier is accessed and subscribed using:

FormViewModel model = Provider.of<FormViewModel>(context);

FormViewModel is created using:

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final appTitle = 'Nothing New';
    return MultiProvider(
      providers: [
        Provider<FormViewModel>(
          create: (_) => FormViewModel(Loading(), FirebaseService(), ImageUploadService()),
        )
      ],
      child: MaterialApp(
        title: "XX",
        home: Scaffold(
          appBar: AppBar(
            title: Text(appTitle),
          ),
          body: MyCustomForm(),
        ),
      ),
    );
  }
}

FormViewModel extends BaseViewModel . I've verified that state is being set correctly, but there's no listeners in the print statements below:

class BaseViewModel<T> with ChangeNotifier {

  T _state;
  T get state => _state;

  BaseViewModel(T viewState) {
    setState(viewState);
  }

  void setState(T viewState) {
    print("state change: $viewState");
    _state = viewState;
    print('has listeners: $hasListeners');
    notifyListeners();
    handleSideEffects(state);
  }

  @protected
  void handleSideEffects(T _state) {
    print("handle side effects for: $_state");
  }

  @protected
  void handleError(Object e) {
    print(e);
  }
}

Answer 1

You're using the wrong provider.

You should use ChangeNotifierProvider if your object is a ChangeNotifier and wants the provider to rebuild dependents when there's a change.

ChangeNotifierProvider<FormViewModel>(
  create: (_) => FormViewModel(Loading(), FirebaseService(), ImageUploadService()),
)