如何使用bloc在App Bar中接收状态

dependencies:
  flutter_bloc: ^7.0.0

import 'package:flutter_bloc/flutter_bloc.dart';

enum AppBarState { loading, loaded }

class AppBarBloc extends Bloc<AppBarState, AppBarState> {
  AppBarBloc() : super(AppBarState.loading);

  @override
  Stream<AppBarState> mapEventToState(AppBarState state) async* {
    // 在这里处理状态变化的逻辑
    yield state;
  }
}

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

class MyAppBar extends StatelessWidget implements PreferredSizeWidget {
  @override
  Size get preferredSize => Size.fromHeight(kToolbarHeight);

  @override
  Widget build(BuildContext context) {
    return BlocBuilder<AppBarBloc, AppBarState>(
      builder: (context, state) {
        // 根据状态更新App Bar
        return AppBar(
          title: Text('My App'),
          actions: [
            if (state == AppBarState.loading)
              CircularProgressIndicator(),
            if (state == AppBarState.loaded)
              IconButton(
                icon: Icon(Icons.refresh),
                onPressed: () {
                  // 处理按钮点击事件
                },
              ),
          ],
        );
      },
    );
  }
}

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

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return BlocProvider(
      create: (context) => AppBarBloc(),
      child: MaterialApp(
        title: 'My App',
        home: Scaffold(
          appBar: MyAppBar(),
          body: Container(),
        ),
      ),
    );
  }
}