如何使用Flutter bloc构建一个文本字段，以便在用户键入时将其值更新为另一个小部件？

dependencies:
  flutter:
    sdk: flutter
  bloc: ^7.0.0
  flutter_bloc: ^7.0.0

import 'package:flutter_bloc/flutter_bloc.dart';

import 'package:bloc/bloc.dart';

class TextFieldBloc extends Bloc<TextFieldEvent, String> {
  TextFieldBloc() : super('');

  @override
  Stream<String> mapEventToState(TextFieldEvent event) async* {
    if (event is TextFieldUpdated) {
      yield event.text;
    }
  }
}

abstract class TextFieldEvent {}

class TextFieldUpdated extends TextFieldEvent {
  final String text;

  TextFieldUpdated(this.text);
}

BlocBuilder<TextFieldBloc, String>(
  builder: (context, state) {
    return TextField(
      onChanged: (text) {
        context.read<TextFieldBloc>().add(TextFieldUpdated(text));
      },
      decoration: InputDecoration(
        labelText: 'Text Field',
      ),
    );
  },
)