How to access Provided (Provider.of()) value insid

问题:

I have a FloatingActionButton inside a widget tree which has a BlocProvider from flutter_bloc. Something like this:

BlocProvider(
  builder: (context) {
    SomeBloc someBloc = SomeBloc();
    someBloc.dispatch(SomeEvent());

    return someBloc;
  },
  child: Scaffold(
    body: ...
    floatingActionButton: FloatingActionButton(
      onPressed: _openFilterSchedule,
      child: Icon(Icons.filter_list),
    ),
  )
);

Which opens a modal bottom sheet:

void _openFilterSchedule() {
    showModalBottomSheet<void>(
      context: context,
      builder: (BuildContext context) {
        return TheBottomSheet();
      },
    );
  }

I am trying to access SomeBloc using BlocProvider.of<SomeBloc>(context) inside TheBottomSheet but I get the following error:

BlocProvider.of() called with a context that does not contain a Bloc of type SomeBloc.

I have tried to use the solution described in https://stackoverflow.com/a/56533611/2457045 but only works for BottomSheet and not ModalBottomSheet.

---

Note: This is not restricted to BlocProvider or flutter_bloc. Any Provider from the provider package has the same behaviour.

How can I access BlocProvider.of<SomeBloc>(context) inside the showModalBottomSheet?

In case it's not possible to do that, how to adapt https://stackoverflow.com/a/56533611/2457045 solution to Modal Bottom Sheet?

回答1:

InheritedWidgets, and therefore Providers, are scoped to the widget tree. They cannot be accessed outside of that tree.

The thing is, using showDialog and similar functions, the dialog is located in a different widget tree – which may not have access to the desired provider.

It is therefore necessary to add the desired providers in that new widget tree:

void myShowDialog() {
  final myModel = Provider.of<MyModel>(context, listen: false);
  showDialog(
    context: context,
    builder: (_) {
      return Provider.value(value: myModel, child: SomeDialog());
    },
  );
}

回答2:

You should split Scaffold widget and its children, to another StatefulWidget

From single Widget

class MainScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return BlocProvider(
      builder: (context) {
        SomeBloc someBloc = SomeBloc();
        someBloc.dispatch(SomeEvent());
        return someBloc;
      },
      child: Scaffold(
        body: ...
        floatingActionButton: FloatingActionButton(
          onPressed: _openFilterSchedule,
          child: Icon(Icons.filter_list),
        ),
      )
    );
  }
}

Splitted into these two widget

class MainScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return BlocProvider(
      builder: (context) {
        SomeBloc someBloc = SomeBloc();
        someBloc.dispatch(SomeEvent());
        return someBloc;
      },
      child: Screen(),
    );
  }
}

and ..

class Screen extends StatelessWidget {

  void _openFilterSchedule() {
    showModalBottomSheet<void>(
      context: context,
      builder: (BuildContext context) {
        return TheBottomSheet();
      },
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: ...
      floatingActionButton: FloatingActionButton(
        onPressed: _openFilterSchedule,
        child: Icon(Icons.filter_list),
      ),
    );
  }
}