FLEX4 URLLoader与后台交互请求XML文件

<?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"    xmlns:amcharts="http://www.amcharts.com/com_internal"   backgroundColor="#FFFFFF"   width="100%" height="100%"   initialize="initializeHandler(event)"><fx:Script>       private var _myService:URLLoader;private function initializeHandler(event:Event):void {_myService = new URLLoader(  );_myService.addEventListener(Event.COMPLETE,myCompleteHandler);_myService.load(new URLRequest("fileName.xml"));XML.ignoreWhitespace = true;}private function myCompleteHandler(event:Event):void {var xml:XML = new XML(_myService.data);myComboBox.dataProvider = xml.children(  );}</fx:Script><mx:VBox><mx:ComboBox id="myComboBox" /></mx:VBox></s:Application>