如何使用Bloc观察流中的变化

dependencies:
  flutter:
    sdk: flutter
  bloc: ^8.0.0
  flutter_bloc: ^8.0.0

import 'package:bloc/bloc.dart';

class MyBloc extends Bloc<Event, State> {
  @override
  State get initialState => InitialState();

  @override
  Stream<State> mapEventToState(Event event) async* {
    if (event is MyEvent) {
      // 处理事件并返回新的状态
      yield NewState();
    }
  }
}

import 'package:equatable/equatable.dart';

abstract class Event extends Equatable {
  const Event();

  @override
  List<Object> get props => [];
}

class MyEvent extends Event {}

import 'package:equatable/equatable.dart';

abstract class State extends Equatable {
  const State();

  @override
  List<Object> get props => [];
}

class InitialState extends State {}

class NewState extends State {}

BlocProvider(
  create: (context) => MyBloc(),
  child: MyWidget(),
)

BlocBuilder<MyBloc, State>(
  builder: (context, state) {
    if (state is InitialState) {
      // 初始状态的UI
      return Text('Initial State');
    } else if (state is NewState) {
      // 新状态的UI
      return Text('New State');
    }
    // 其他状态的UI
    return Container();
  },
)