Flutter 使用不包含类型为的BLoC的上下文调用的Flatter BLoC BlocProvider.of（）

与之类似，到目前为止还没有相关的解决方案

我得到以下错误：

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

class _TestWidgetState extends State<TestWidget> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Test')),
      body: BlocProvider(
        builder: (context) => sl<CategoryBloc>(),   // dependency injection via GetIt
        child: Column(
          children: [
            BlocBuilder<CategoryBloc, CategoryState>(builder: (context, state) {
              if (state is Empty) {
                return Text('Empty');
              }
              if (state is Loading) {
                return Text('Loading');
              }
              if (state is Loaded) {
                return Text('Loaded');
              }
            }),
            RaisedButton(
              child: Text('Press me'),
              onPressed: () {
                dispatchAction(context);
              },
            ),
          ],
        ),
      ),
    );
  }

  void dispatchAction(BuildContext context) {
    BlocProvider.of<CategoryBloc>(context).dispatch(GetAllCategories());
  }
}

唯一的小部件：

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

class _TestWidgetState extends State<TestWidget> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Test')),
      body: BlocProvider(
        builder: (context) => sl<CategoryBloc>(),   // dependency injection via GetIt
        child: Column(
          children: [
            BlocBuilder<CategoryBloc, CategoryState>(builder: (context, state) {
              if (state is Empty) {
                return Text('Empty');
              }
              if (state is Loading) {
                return Text('Loading');
              }
              if (state is Loaded) {
                return Text('Loaded');
              }
            }),
            RaisedButton(
              child: Text('Press me'),
              onPressed: () {
                dispatchAction(context);
              },
            ),
          ],
        ),
      ),
    );
  }

  void dispatchAction(BuildContext context) {
    BlocProvider.of<CategoryBloc>(context).dispatch(GetAllCategories());
  }
}

为完整起见，我将提供所有集团文件

类别bloc

class CategoryBloc extends Bloc<CategoryEvent, CategoryState> {
  final GetAllCategoriesUsecase getAllCategories;

  CategoryBloc({@required this.getAllCategories})
      : assert(getAllCategories != null);

  @override
  CategoryState get initialState => Empty();

  @override
  Stream<CategoryState> mapEventToState(CategoryEvent event) async* {
    if (event is GetAllCategories) {
      yield Loading();
      final failureOrCategories =
          await getAllCategories(Params(limit: 10, skip: 0));
      yield failureOrCategories.fold(
          (failure) => Error(error: _mapFailureToMessage(failure)),
          (categories) => Loaded(list: categories));
    }
  }

  String _mapFailureToMessage(Failure failure) {
    ...
  }
}

到目前为止，我已经尝试：

• 指定类型

  正文：BlocProvider（

  -相同错误

---

任何帮助都会受到极大的欢迎。

在谷歌搜索数小时后找到了答案

Flatter_bloc要求BlocProvider和BlocBuilder位于单独的小部件中，这样bloc Builder的上下文在层次结构上“位于”Builder的上下文之下

class _TestWidgetState extends State<TestWidget> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Test')),
      body: BlocProvider<CategoryBloc>(
        builder: (context) => sl<CategoryBloc>(), //
        child: TestWidget2(),
      ),
    );
  }
}

class TestWidget2 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        BlocBuilder<CategoryBloc, CategoryState>(builder: (context, state) {
          if (state is Empty) {
            return Text('Empty');
          }
          if (state is Loading) {
            return Text('Loading');
          }
          if (state is Loaded) {
            return Text('Loaded');
          }
        }),
        RaisedButton(
          child: Text('Press me'),
          onPressed: () {
            dispatchAction(context);
          },
        ),
      ],
    );
  }

class\u TestWidgetState扩展状态{
@凌驾
小部件构建（构建上下文）{
返回脚手架(
appBar:appBar（标题：Text（'Test'）），
正文：BlocProvider(
生成器：（上下文）=>sl（）//
子项：TestWidget2（），
),
);
}
}
类TestWidget2扩展了无状态小部件{
@凌驾
小部件构建（构建上下文）{
返回列(
儿童：[
BlocBuilder（生成器：（上下文，状态）{
如果（状态为空）{
返回文本（'Empty'）；
}
如果（状态为正在加载）{
返回文本（“加载”）；
}
如果（状态已加载）{
返回文本（“已加载”）；
}
}),
升起的按钮(
child:Text（'Press me'），
已按下：（）{
调度行动（上下文）；
},
),
],
);
}

以下是该问题的解决方案：

  get_it: ^3.0.1
  flutter_bloc: ^0.21.0   # old version :(
  equatable: ^1.0.1

class _TestWidgetState extends State<TestWidget> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Test')),
      body: BlocProvider<CategoryBloc>(
        builder: (context) => sl<CategoryBloc>(), //
        child: TestWidget2(),
      ),
    );
  }
}

class TestWidget2 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        BlocBuilder<CategoryBloc, CategoryState>(builder: (context, state) {
          if (state is Empty) {
            return Text('Empty');
          }
          if (state is Loading) {
            return Text('Loading');
          }
          if (state is Loaded) {
            return Text('Loaded');
          }
        }),
        RaisedButton(
          child: Text('Press me'),
          onPressed: () {
            dispatchAction(context);
          },
        ),
      ],
    );
  }