Flex如何利用样式改变默认文件夹和子项目图标的例子

<?xml version="1.0" encoding="utf-8"?> 
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" 
        layout="vertical" 
        verticalAlign="middle" 
        backgroundColor="white"> 
  
    <mx:Script> 
        <![CDATA[ 
            [Bindable] 
            [Embed("assets/folder.png")] 
            private var myFolderClosedIcon:Class; 
  
            [Bindable] 
            [Embed("assets/folder_page.png")] 
            private var myFolderOpenIcon:Class; 
  
            [Bindable] 
            [Embed("assets/arrow_right.png")] 
            private var myDefaultLeafIcon:Class; 
        ]]> 
    </mx:Script> 
  
    <mx:XML id="dp"> 
        <mlb> 
            <league label="American League"> 
                <division label="East"> 
                    <team label="Boston" /> 
                    <team label="New York" /> 
                    <team label="Toronto" /> 
                    <team label="Baltimore" /> 
                    <team label="Tampa Bay" /> 
                </division> 
                <division label="Central"> 
                    <team label="Cleveland" /> 
                    <team label="Detroit" /> 
                    <team label="Minnesota" /> 
                    <team label="Chicago" /> 
                    <team label="Kansas City" /> 
                </division> 
                <division label="West"> 
                    <team label="Los Angeles" /> 
                    <team label="Seattle" /> 
                    <team label="Oakland" /> 
                    <team label="Texas" /> 
                </division> 
            </league> 
        </mlb> 
    </mx:XML> 
  
    <mx:Tree id="TreeProject" 
            dataProvider="{dp.league}" 
            labelField="@label" 
            showRoot="true" 
            defaultLeafIcon="{myDefaultLeafIcon}" 
            folderOpenIcon="{myFolderOpenIcon}" 
            folderClosedIcon="{myFolderClosedIcon}" 
            width="320" 
            height="240" /> 
  
</mx:Application>