Flutter--EventBus

首先要引用event_bus.dart文件

初始化EventBus全局对象

生成一个event类，也可以用父类event来传递

在需要监听总线的页面添加监视器，类型是StreamSubscription，可以指定监听的event类型，不符合的event不会被监听到

发送事件可以用EventBus.fire(event)方法，其中的event可以是普通event，也可以是自定event

一个例子：

import 'dart:async';

import 'package:flutter/cupertino.dart';
import "package:flutter/material.dart";
import 'package:flutter/rendering.dart';
import "package:flutter/src/material/dialog.dart";
import 'package:flutter/gestures.dart';
import 'package:event_bus/event_bus.dart';
import 'package:flutter/services.dart';

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



EventBus _bus = EventBus();
int i =0;
class changeThemeColorCEvent {
  Color color;
  changeThemeColorCEvent(this.color);

}

class MyApp extends StatelessWidget{


  @override
  Widget build(BuildContext context) {
    //_bus.on<changeThemeColorCEvent>().listen((event){print(event); print(i++);});
    return MaterialApp(
      title:'fuck',
      home: TestPage(),
    );
  }


}


class TestPage extends StatefulWidget {



  TestPage ({Key key}): super( key :key);

  @override
  State<StatefulWidget> createState() {
    // TODO: implement createState
    return TestPageState();
  }
}

class TestPageState extends State<TestPage> {

  StreamSubscription sub;

  Future<String> wait5Second() async {
    return Future.delayed(Duration(seconds: 5),() => "我是数据");
  }

  @override
  void initState() {
    // TODO: implement initState
    super.initState();
      sub= _bus.on<changeThemeColorCEvent>().listen((event){
      print(event);
    });
  }

  
  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return Scaffold(
      appBar: AppBar(title: Text('futureBuilder测试'),),
    body:
      Center(
      child:
          FlatButton(
            child: Text('点我'),
            onPressed: () => Navigator.push(context, CupertinoPageRoute(builder: (context) => anotherPage())),
          )
    ));
  }

  @override
  void dispose() {
    // TODO: implement dispose
    super.dispose();
    sub.cancel();
  }


}


class anotherPage extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    // TODO: implement createState
    return anotherPageState();
  }
}

class anotherPageState extends State<anotherPage> {
  

  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return Container(color: Colors.white,
    child:
      RaisedButton(
        child: Text('点我'),
        onPressed: ()
        {
          _bus.fire(changeThemeColorCEvent(Colors.red));
        },
      ),
    );
  }

}

不生成监听器（streamsubscription）也可以监听，但每次调用bus.on<xx>.listen()都会生成一个新的streamsubscription，所以将上面代码改成下面这样的，热重载一下，会发现每次fire event，会print两次。因为热重载（ressemble）是调用didUpdateWidget和build，build里会重新生成一个streamsubscription。

import 'dart:async';

import 'package:flutter/cupertino.dart';
import "package:flutter/material.dart";
import 'package:flutter/rendering.dart';
import "package:flutter/src/material/dialog.dart";
import 'package:flutter/gestures.dart';
import 'package:event_bus/event_bus.dart';void main() => runApp(MyApp());



EventBus _bus = EventBus();
int i =0;
class changeThemeColorCEvent {
  Color color;
  changeThemeColorCEvent(this.color);

}

class MyApp extends StatelessWidget{


  @override
  Widget build(BuildContext context) {
    _bus.on<changeThemeColorCEvent>().listen((event){print(event); print(i++);});
    return MaterialApp(
      title:'fuck',
      home: TestPage(),
    );
  }


}


class TestPage extends StatefulWidget {



  TestPage ({Key key}): super( key :key);

  @override
  State<StatefulWidget> createState() {
    // TODO: implement createState
    return TestPageState();
  }
}

class TestPageState extends State<TestPage> {

//  StreamSubscription sub;

  Future<String> wait5Second() async {
    return Future.delayed(Duration(seconds: 5),() => "我是数据");
  }

  @override
  void initState() {
    // TODO: implement initState
    super.initState();
//      sub= _bus.on<changeThemeColorCEvent>().listen((event){
//      print(event);
//    });
  }

  @override
  void didUpdateWidget(TestPage oldWidget) {
    // TODO: implement didUpdateWidget
    print('didUpdateWidget');
    super.didUpdateWidget(oldWidget);
  }
  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return Scaffold(
      appBar: AppBar(title: Text('futureBuilder测试'),),
    body:
      Center(
      child:
          FlatButton(
            child: Text('点我'),
            onPressed: () => Navigator.push(context, CupertinoPageRoute(builder: (context) => anotherPage())),
          )
    ));
  }

  @override
  void dispose() {
    // TODO: implement dispose
    super.dispose();
//    sub.cancel();
  }


}


class anotherPage extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    // TODO: implement createState
    return anotherPageState();
  }
}

class anotherPageState extends State<anotherPage> {
  @override
  void didUpdateWidget(anotherPage oldWidget) {
    // TODO: implement didUpdateWidget
    print('didupdate');
    super.didUpdateWidget(oldWidget);
  }

  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return Container(color: Colors.white,
    child:
      RaisedButton(
        child: Text('点我'),
        onPressed: ()
        {
          _bus.fire(changeThemeColorCEvent(Colors.red));
        },
      ),
    );
  }

  @override
  void dispose() {
    // TODO: implement dispose
    super.dispose();
  }
}