Flex的List拖拽事件选择来源控件

朋友说他要做的程序上有两组可以互相拖拽的List,大家都知道Flex实现拖拽操作非常简单，只需要在List组件上设置 dragEnabled="true" dropEnabled="true" 两个属性即可，但他的问题是两组List,只能在一组内拖动，不能拖到另一组,所以帮他写了个小例子，判断拖拽的来源组件，只接受来自一个组件的拖拽。代码如下

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="horizontal">
	<mx:Script>
		<![CDATA[
			import mx.events.DragEvent;
			import mx.collections.ArrayCollection;
			private var dataList:ArrayCollection = new ArrayCollection([{name:"a"}]);
			private var dataList2:ArrayCollection = new ArrayCollection([{name:"b"}]);
			private var dataList3:ArrayCollection = new ArrayCollection([{name:"c"}]);
			
			private function dragEnterHandler(e:DragEvent):void{
				if((e.dragInitiator as List).id !="l3")e.preventDefault();
			}
			private function dragCompleteHandler(e:DragEvent):void{
				if((e.dragInitiator as List).id !="l3")e.preventDefault();
			}
			
			private function dragOverHandler(e:DragEvent):void{
				if((e.dragInitiator as List).id !="l3")e.preventDefault();
			}
		]]>
	</mx:Script>
	<mx:List initialize="l1.dataProvider=dataList" id="l1" labelField="name" dragEnabled="true" dropEnabled="true" dragMoveEnabled="true" width="100"></mx:List>
	<mx:List  id="l2" labelField="name" dragEnabled="true" dropEnabled="true" dragOver="dragOverHandler(event)" dragComplete="dragCompleteHandler(event)" dragEnter="dragEnterHandler(event)" dragMoveEnabled="true" width="100"></mx:List>
	<mx:List initialize="l3.dataProvider=dataList3" id="l3" labelField="name" dragEnabled="true" dropEnabled="true" dragMoveEnabled="true" width="100"></mx:List>
	
</mx:Application>