Flex4 事件机制3

? ?? 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,priority:int=0,useWeakReference:Boolean=true):void
		{
			eventDispatcher.removeEventListener(type,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>