dart笔记20：基于Bloc stream流实现数据处理和UI渲染分离

基于Bloc stream流实现数据处理和UI渲染分离：

bloc_base.dart文件用来强制销毁stream

abstract class BlocBase {
  void dispose();
}

bloc_counter.dart实例化StreamController，同时实现两个方法，内部方法_counter往流里面塞内容，外部方法counter往外“吐”出内容：

import 'dart:async';
import 'bloc_base.dart';

class BlocCounter extends BlocBase {
  final _controller = StreamController<int>();

  get _counter => _controller.sink;

  get counter => _controller.stream;

  void increment(int count) {
    _counter.add(++count);
  }

  @override
  void dispose() {
    _controller.close();
  }
}

main.dart调用bloc_counter的外部方法，往流里面塞内容：

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

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'bloc示例',
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key}) : super(key: key);

  @override
  _MyHomePageState createState() => _MyHomePageState(BlocCounter());
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  final BlocCounter bloc;

  _MyHomePageState(this.bloc);

  void _incrementCounter() {
    bloc.increment(_counter);
  }

  @override
  void initState() {
    bloc.counter.listen((_count) {
      setState(() {
        _counter = _count;
      });
    });
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('StreamBuilder示例'),
      ),
      body: Center(
        child: Text(
          '$_counter',
          // ignore: deprecated_member_use
          style: Theme.of(context).textTheme.display1,
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        child: Icon(Icons.add),
      ),
    );
  }

  @override
  void dispose() {
    super.dispose();
  }
}