flex中关于文件的的添加和删除问题

<?xml version="1.0" encoding="utf-8"?><s:WindowedApplication xmlns:fx="http://ns.adobe.com/mxml/2009"    xmlns:s="library://ns.adobe.com/flex/spark"    xmlns:mx="library://ns.adobe.com/flex/mx"><fx:Declarations><!-- 将非可视元素（例如服务、值对象）放在此处 --></fx:Declarations><fx:Script><![CDATA[import flash.events.Event;import flash.filesystem.File;import flash.filesystem.FileMode;import flash.filesystem.FileStream;import mx.controls.Alert;private var outputFolderFile:File = new File();private var strFile:File;private function saveHandler(event:MouseEvent):void{outputFolderFile.browseForDirectory("Select Directory");outputFolderFile.addEventListener(Event.SELECT, directorySelectedHandler);}private function directorySelectedHandler(e:Event):void{strFile = outputFolderFile.resolvePath("李虎.txt");saveWritedUtfBytes(strFile, taStr.text);}public function saveWritedUtfBytes(file:File, data:String):void{try{var fileStream:FileStream = new FileStream();fileStream.open(file, FileMode.WRITE);fileStream.position = 0;fileStream.writeUTFBytes(data);fileStream.close();taStr.text="";}catch(e:Error){trace("字符串写入失败");}}private function deleteHandler(evt:MouseEvent):void{if(strFile.exists);{strFile.deleteFile();Alert.show("删除成功！");}}]]></fx:Script><s:VGroup top="10" left="10"><s:Label text="请输入一串字符:"/><s:TextArea id="taStr" width="200"/><s:Button width="80" height="30" label="保存" click="saveHandler(event)"/><s:Button width="80" height="30" label="删除" click="deleteHandler(event)"/></s:VGroup></s:WindowedApplication>