Flex4 事件机制3

本文主要是介绍Flex4 事件机制3，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

     Flex中所有的组件都间接继承自EventDispatcher，通过查看Flex API，了解一下这个类中的方法。         如图所见，该类包含了派发事件、监听事件、移出事件等方法，那么通过这个类就可以实现本文开篇所提出的那种情况，分析一下，监听事件的对象和派发事件的对象必须是同一个对象，这样事件才能被捕获，所以我们需要写一个单例的类，并且组合EventDispatcher，可以满足需求。

      myevents/TestEventDispatcher.as只是测试用。

package events
{import events.MyEvent;	import flash.events.Event;import flash.events.EventDispatcher;import flash.events.IEventDispatcher;	import mx.core.Singleton;public class TestEventDispatcher{private static var _inst:MyEventDispatcher;private var eventDispatcher:IEventDispatcher;public function MyEventDispatcher(singleton:Singleton){if(singleton == null){throw new Error("Create MyEventDispatcher Error!");}eventDispatcher = new EventDispatcher();}public static function getInstance():MyEventDispatcher{if (!_inst){_inst = new MyEventDispatcher(new Singleton);}return _inst;}public function addEventListener(type:String, listener:Function, useCapture:Boolean=false, pririty:int=0, useWeakReference:Boolean=true):void{eventDispatcher.addEventListener(type, listener, useCapture, pririty, useWeakReference);}public function removeEventListener(type:String, listener:Function, useCapture:Boolean=false, priority:int=0, useWeakReference:Boolean=true):void{eventDispatcher.removeEventListener(type, listener, useCapture);}public function dispatchEvent(event:MyEvent):Boolean{return eventDispatcher.dispatchEvent(event);}public function hasEventListener(type:String):Boolean{return eventDispatcher.hasEventListener(type);}public function willTrigger(type:String):Boolean{return eventDispatcher.willTrigger(type);}}
}
class Singleton {}

events/MyEvent.as，我们可以在该类中加入一个dispatch方法，创建完事件之后可以派发，代码如下：      

/*** 派发事件* @return */
public function dispatch():Boolean
{return MyEventDispatcher.getInstance().dispatchEvent(this);
}

 这样，创建完自定义事件之后，就可以直接派发事件了，那么使用起来就很方便了，下面是具体使用代码，一个应用中有两个自定义组件，组件一中有个TextArea，组件二中有个按钮，点击按钮，将数据传递到TextArea中。

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" xmlns:s="library://ns.adobe.com/flex/spark" xmlns:mx="library://ns.adobe.com/flex/mx" minWidth="955" minHeight="600" xmlns:components="components.*"><s:layout><s:VerticalLayout/></s:layout><components:component1 /><components:component2 />
</s:Application>

   components/component1.mxml

<?xml version="1.0" encoding="utf-8"?>
<s:Group xmlns:fx="http://ns.adobe.com/mxml/2009" xmlns:s="library://ns.adobe.com/flex/spark" xmlns:mx="library://ns.adobe.com/flex/mx"creationComplete="creationCompleteHandler(event)"><fx:Script><![CDATA[import events.MyEventDispatcher;import events.MyEvent;import mx.events.FlexEvent;			protected function creationCompleteHandler(event:FlexEvent):void{MyEventDispatcher.getInstance().addEventListener(MyEvent.SHOWINFO, showInfo);}			protected function showInfo(event:MyEvent):void{textArea.text = event.data;}			]]></fx:Script><s:TextArea id="textArea" />
</s:Group>

components/component2.mxml

<?xml version="1.0" encoding="utf-8"?>
<s:Group xmlns:fx="http://ns.adobe.com/mxml/2009" xmlns:s="library://ns.adobe.com/flex/spark" xmlns:mx="library://ns.adobe.com/flex/mx">	<fx:Script><![CDATA[import events.MyEvent;import events.MyEventDispatcher;protected function buttonClickHandler(event:MouseEvent):void{var myEvent:MyEvent = new MyEvent(MyEvent.SHOWINFO);myEvent.data = "哈哈";myEvent.dispatch();}]]></fx:Script><s:Button label="显示内容" click="buttonClickHandler(event)"/>
</s:Group>

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