Flutter 状态管理之Bloc

定义bloc

import 'dart:async';

import 'package:flutter/material.dart';

class CounterHome extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    CounterBloc _counterBloc = CounterProvider.of(context).bloc;
    return StreamBuilder(
      initialData: 0,
      stream: _counterBloc.count,
      builder: (context, snapshot) {
        return Center(
          child: ActionChip(
            label: Text('${snapshot.data}'),
            onPressed: () {
              _counterBloc.counter.add(1);
            },
          ),
        );
      },
    );
  }
}

class CounterActionButton extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    CounterBloc _counterBloc = CounterProvider.of(context).bloc;
    return FloatingActionButton(
      child: Icon(Icons.add),
      onPressed: () {
        _counterBloc.counter.add(1);
      },
    );
  }
}

class CounterProvider extends InheritedWidget {
  CounterProvider({Key key, this.child, this.bloc})
      : super(key: key, child: child);

  final Widget child;
  final CounterBloc bloc;

  static CounterProvider of(BuildContext context) {
    return (context.inheritFromWidgetOfExactType(CounterProvider)
        as CounterProvider);
  }

  @override
  bool updateShouldNotify(CounterProvider oldWidget) {
    return true;
  }
}

class CounterBloc {
  int _count = 0;
  final _counterActionController = StreamController<int>();
  StreamSink<int> get counter => _counterActionController.sink;

  final _counterController = StreamController<int>();
  Stream<int> get count => _counterController.stream;

  CounterBloc() {
    _counterActionController.stream.listen(onData);
  }

  void disponse() {
    _counterActionController.close();
    _counterController.close();
  }

  void onData(int data) {
    print('$data');
    _count = data + _count;
    _counterController.add(_count);
  }

  void log() {
    print('BloC');
  }
}

使用

import './counter_bloc_demo.dart';

class BlocDemo extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return CounterProvider(
      bloc: CounterBloc(),
      child:Scaffold(
          appBar: AppBar(
            title: Text('BlocDemo'),
            elevation: 0.0,
          ),
          body: CounterHome(),
          floatingActionButton: CounterActionButton(),
        ),
      
    );
  }
}