FLEX4中使用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>