如何使用bloc未来获取流过滤来自后台的数据？

dependencies:
  flutter_bloc: ^7.0.0

abstract class MyEvent {}

class FetchDataEvent extends MyEvent {}

abstract class MyState {}

class DataLoadedState extends MyState {
  final List<Data> dataList;

  DataLoadedState(this.dataList);
}

class MyBloc extends Bloc<MyEvent, MyState> {
  final MyRepository repository;

  MyBloc(this.repository) : super(DataLoadedState([]));

  @override
  Stream<MyState> mapEventToState(MyEvent event) async* {
    if (event is FetchDataEvent) {
      try {
        // 从后台获取数据
        List<Data> dataList = await repository.fetchData();

        // 发送数据加载成功的状态
        yield DataLoadedState(dataList);
      } catch (e) {
        // 发送数据加载失败的状态
        yield DataLoadFailedState();
      }
    }
  }
}

class MyPage extends StatefulWidget {
  @override
  _MyPageState createState() => _MyPageState();
}

class _MyPageState extends State<MyPage> {
  late MyBloc _bloc;

  @override
  void initState() {
    super.initState();
    _bloc = MyBloc(MyRepository());
    _bloc.add(FetchDataEvent());
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      // 界面内容
    );
  }

  @override
  void dispose() {
    _bloc.close();
    super.dispose();
  }
}

BlocBuilder<MyBloc, MyState>(
  bloc: _bloc,
  builder: (context, state) {
    if (state is DataLoadedState) {
      // 数据加载成功，显示数据列表
      return ListView.builder(
        itemCount: state.dataList.length,
        itemBuilder: (context, index) {
          return ListTile(
            title: Text(state.dataList[index].title),
            // 其他数据展示
          );
        },
      );
    } else if (state is DataLoadFailedState) {
      // 数据加载失败，显示错误信息
      return Text('Failed to load data');
    } else {
      // 数据加载中，显示加载动画
      return CircularProgressIndicator();
    }
  },
)