flex4基于datGroup自定义布局实例
2、 ss.mxml

2、 SimpleItemRenderer.mxml






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）}}}}