flex4基于datGroup自定义布局实例

2、 ss.mxml

<?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/halo"
			   xmlns:local="*"
			   creationComplete="init();">
	
		<fx:Script>
			<![CDATA[
				import mx.collections.ArrayCollection;
				
				private var dataSource:ArrayCollection = new ArrayCollection();
				
				public function init():void{
					for(var i:int = 0; i < 10; i++){
						dataSource.addItem(i);
					}
					dataGroupID.dataProvider = dataSource;
				}
				
			]]>
		</fx:Script>
	
		<s:DataGroup id="dataGroupID" width="100%" height="100%" itemRenderer="SimpleItemRenderer">
			<s:layout>
				<local:CircularLayout />  <!--自定义布局类:CircularLayout.其只在DataGroup初始化的时候执行一次-->
			</s:layout>
		</s:DataGroup>
		
		<mx:Button label="点击添加按钮" click="dataSource.addItem(dataSource.length)" />
	
</s:Application>

2、 SimpleItemRenderer.mxml

<s:ItemRenderer xmlns:fx="http://ns.adobe.com/mxml/2009"
				xmlns:s="library://ns.adobe.com/flex/spark" 
				xmlns:mx="library://ns.adobe.com/flex/halo">
	
	<s:layout>
		<s:BasicLayout/>
	</s:layout>
	<s:Button label="{this.data}"/>
	
</s:ItemRenderer>

3、CircularLayout.as 

package{
	import mx.core.ILayoutElement;
	import spark.layouts.supportClasses.LayoutBase;
	
	public class CircularLayout extends LayoutBase{
		override public function updateDisplayList(w:Number, h:Number):void{
			super.updateDisplayList(w, h);
			var layoutElement:ILayoutElement;
			if(!target){
				return;
			}
			var count:uint = target.numElements;    //当前dataGroup容器里的所有组件的总数量
			var w2:Number = target.width;     //当前浏览器的宽度
			var h2:Number = target.height;    //当前浏览器的高度
			for(var i:int = 0; i < count; i++){
				layoutElement = target.getElementAt(i);
				if (!layoutElement || !layoutElement.includeInLayout){
					continue;
				}
				layoutElement.setLayoutBoundsPosition(i * 100, i + 350);    //对每一个组件进行遍历及定位（分别表示x、y轴）（核心啊）
			}
		}
		
	}
	
}