flutter - 在 dispose 方法中访问 BlocProvider.of(context)

Question

有没有人知道我如何做到这一点？

我的代码:

  @override
  void dispose() {
    final FiltersBloc filtersBloc = 
       BlocProvider.of<FiltersBloc>(context);
    super.dispose();
  }

错误是:

flutter:         BlocProvider.of() called with a context that does not contain a Bloc of type FiltersBloc.
flutter:         No ancestor could be found starting from the context that was passed to
flutter: BlocProvider.of<FiltersBloc>().
flutter:
flutter:         This can happen if:
flutter:         1. The context you used comes from a widget above the BlocProvider.
flutter:         2. You used MultiBlocProvider and didn't explicity provide the BlocProvider types.
flutter:
flutter:         Good: BlocProvider<FiltersBloc>(builder: (context) => FiltersBloc())
flutter:         Bad: BlocProvider(builder: (context) => FiltersBloc()).
flutter:
flutter:         The context used was: FiltersDrawer(dirty, state: _FiltersDrawerState#86e8a)

另外，如果我遵循错误代码并使用 final filtersBloc = BlocProvider<FiltersBloc>(builder: (context) => FiltersBloc())相反，我无法拨打 filtersBloc.dispatch()了。

我知道对于 initState，我们可以只是 didChangeDependencies反而。但是我找不到对应的 dispose。

任何帮助将不胜感激。谢谢!

Answer 1

BlockProvider 需要初始化上下文。您可以在屏幕的 Widget build() 上初始化它

late FiltersBloc filtersBloc;

@override
Widget build(BuildContext context){
  filtersBloc = BlocProvider.of<FiltersBloc>(context);
  return ...
}

...然后在 dispose() 上调用所需的方法

@override
void dispose() {
  filtersBloc.dispatch();
  super.dispose();
}