Question 221958 in Flutter Question posted in
The official Flutter documentation can be found here.

Flutter can't initialize BLoC provider in the didChangeDependencies()

Good morning, In my Flutter journal project I have HomeBlocProvider and HomeBloc.
In the Home page I am initializing the HomeBloc in the didChangeDependencies() function but somehow it doesn’t initialize

In the build() I am declaring the variable
HomeBloc? _homeBloc;

and this is the didChangeDependencies()

    @override
    void didChangeDependencies() {
      super.didChangeDependencies();
      _homeBloc = HomeBlocProvider.of(context).homeBloc;
    }

The body property of the Scaffold() is StreamBuilder() and the stream property of it I am listening to the _homeBloc!.listJournal

When I run the project I got this error
Exception caught by widgets library
The following _CastError was thrown building Home(dirty, state: _HomeState#ada70):
Null check operator used on a null value

So it seems like the homeBloc still null

This is the code of the HomeBlocProvider

class HomeBlocProvider extends InheritedWidget {
  const HomeBlocProvider({Key? key, required Widget child, this.homeBloc, this.uid}) : super(key: key, child: child);

  @override
  bool updateShouldNotify(HomeBlocProvider oldWidget) => homeBloc != oldWidget.homeBloc;

  static HomeBlocProvider of(BuildContext context) {
    return (context.dependOnInheritedWidgetOfExactType<HomeBlocProvider>() as HomeBlocProvider);
  }

  final HomeBloc? homeBloc;
  final String? uid;
}

I tried to print a string in the didChangeDependecies() and nothing printed so it seems that it doesn’t even execute the function

Tags:

2

Answers


  1. 0

    Have you tried this?

      late HomeBloc _homeBloc;

  @override
  void initState() {
    super.initState();
    _homeBloc = HomeBlocProvider.of(context).homeBloc;
  }

  @override
  Widget build(BuildContext context) {
    ...
  }
    Login or Signup to reply.
  2. 0

    The didChangeDependencies() method is called when the dependencies of the widget change, which can happen during the widget’s lifecycle. However, it’s not guaranteed to be called every time the widget is rebuilt.

    In your case, the HomeBloc initialization logic should be placed in the initState() method instead of didChangeDependencies(). The initState() method is called exactly once when the widget is inserted into the widget tree.

    @override
void initState() {
  super.initState();

  _homeBloc = HomeBlocProvider.of(context).homeBloc;
}

    Also, make sure that HomeBloc is initialized and provided properly to widget tree.

    Login or Signup to reply.
Please signup or login to give your own answer.

Back To Top
Search