如何使用flutter_blocs在树中向下传递数据？

import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';

// 步骤2：创建一个BLoC类
class DataBloc extends Bloc<DataEvent, String> {
  DataBloc() : super('Initial Data');

  @override
  Stream<String> mapEventToState(DataEvent event) async* {
    if (event is UpdateDataEvent) {
      yield event.data;
    }
  }
}

// 步骤4：在子Widget中使用BlocBuilder或BlocConsumer订阅BLoC的状态变化
class ChildWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return BlocBuilder<DataBloc, String>(
      builder: (context, data) {
        return Text(data);
      },
    );
  }
}

// 步骤3：在父级Widget中使用BlocProvider包装子Widget
class ParentWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return BlocProvider<DataBloc>(
      create: (context) => DataBloc(),
      child: ChildWidget(),
    );
  }
}

// 步骤5：在需要向下传递数据的Widget中使用BLoC实例中的数据
class AnotherWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final dataBloc = BlocProvider.of<DataBloc>(context);
    return RaisedButton(
      onPressed: () {
        // 更新数据
        dataBloc.add(UpdateDataEvent('New Data'));
      },
      child: Text('Update Data'),
    );
  }
}

// 步骤1：使用flutter_bloc库的依赖
void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Flutter BLoC Example'),
        ),
        body: Column(
          children: [
            ParentWidget(),
            AnotherWidget(),
          ],
        ),
      ),
    );
  }
}

// 步骤2：定义事件类
abstract class DataEvent {}

class UpdateDataEvent extends DataEvent {
  final String data;

  UpdateDataEvent(this.data);
}