块未在initstate中添加

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

class MyWidget extends StatefulWidget {
  @override
  _MyWidgetState createState() => _MyWidgetState();
}

class _MyWidgetState extends State<MyWidget> {
  MyBloc _myBloc; // 声明一个BLoC

  @override
  void initState() {
    super.initState();
    _myBloc = MyBloc(); // 初始化BLoC
  }

  @override
  void dispose() {
    _myBloc.close(); // 在dispose()方法中关闭BLoC
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return BlocProvider(
      create: (context) => _myBloc, // 在BlocProvider中提供BLoC
      child: Scaffold(
        appBar: AppBar(
          title: Text('My App'),
        ),
        body: BlocBuilder<MyBloc, MyState>(
          builder: (context, state) {
            // 根据状态构建UI
            return Container(
              child: Text('Current state: $state'),
            );
          },
        ),
      ),
    );
  }
}

class MyBloc extends Bloc<MyEvent, MyState> {
  @override
  MyState get initialState => MyInitial();

  @override
  Stream<MyState> mapEventToState(MyEvent event) async* {
    // 处理事件并返回新的状态
    if (event is MyEvent1) {
      yield MyState1();
    } else if (event is MyEvent2) {
      yield MyState2();
    }
  }
}

abstract class MyEvent {}

class MyEvent1 extends MyEvent {}

class MyEvent2 extends MyEvent {}

abstract class MyState {}

class MyInitial extends MyState {}

class MyState1 extends MyState {}

class MyState2 extends MyState {}