flex 打开指定类型的打开对话框

<?xml version="1.0" encoding="utf-8"?> 
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" fontSize="16" layout="absolute">

<mx:Script> 
<![CDATA[
import flash.events.Event;
import flash.net.FileFilter;
import flash.net.FileReference;
import flash.net.FileReferenceList;

private var fileRL:FileReferenceList;

/**
 * 1、imgStr:String --- 是弹出对话框下面的"文件类型(T):"下拉框里面的值，可随便写
 * 2、str:String --- 是列出的在弹出框主面板上显示的这些指定类型的文件
 **/
private function showWindow(imgStr:String, str:String):void
{
fileRL = new FileReferenceList();
fileRL.browse([new FileFilter(imgStr, str)]); 
fileRL.addEventListener(Event.SELECT, onFileSelect); 
}            

private function onFileSelect(event:Event):void
{ 
for(var i:int = 0; i < fileRL.fileList.length; i++){ 
var fr:FileReference = FileReference(fileRL.fileList[i]);  
textID.text = fr.name;                   
}                
}