flex tree节点的图标标记

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"    layout="horizontal" viewSourceURL="srcview/index.html"> 
  <mx:Script>    
   <![CDATA[                        
    [Bindable]      
    [Embed("Resources/ans.png")] 
    public var myFolderClosedIcon:Class;   
    [Bindable]        
    [Embed("Resources/EXIT.png")] 
    public var myFolderOpenIcon:Class; 
[Bindable]         
[Embed("Resources/Dial.png")]     
public var pdfIcon:Class;         
[Bindable]       
[Embed("Resources/hang.png")] 
public var docIcon:Class;                 
                                              ]]>  
                                               </mx:Script>
  <mx:XML id="xmlData" xmlns="">    
     <rootNode>   
      <directory label="dir">    
       <file icon="pdfIcon" label="label1"  />     
        <file icon="docIcon" label="label2"  />    
      </directory>      
      <directory label="dir1">    
        <file icon="docIcon" label="label3"  />      
        <file icon="pdfIcon" label="label4"  />   
      </directory>  
    </rootNode>  
    </mx:XML> 
   
      <mx:Panel title="Tree">         
          <mx:Tree      
                 borderStyle="none"    
                    backgroundAlpha="0"    
                       labelField="@label"    
                          iconField="@icon"      
                             width="300"      
                               height="200"   
                                   id="treeAdmin"   
                                       folderOpenIcon="{myFolderOpenIcon}"  
                                            folderClosedIcon="{myFolderClosedIcon}"       
                                                   dataProvider="{xmlData.directory}"
                                                   alpha="1" />           
             </mx:Panel></mx:Application>