BUTTON的ICON设置

<?xml version="1.0" encoding="utf-8"?> 
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" 
        layout="vertical" 
        verticalAlign="middle" 
        backgroundColor="white"> 
  
    <mx:Style> 
        .addButton { 
            icon: Embed(source="images/bullet_add.png"); 
            disabledIcon: Embed(source="images/bullet_delete.png"); 
        } 
    </mx:Style> 
  
    <mx:ApplicationControlBar dock="true"> 
        <mx:CheckBox id="checkBox" 
                label="enabled:" 
                labelPlacement="left" 
                selected="true" /> 
    </mx:ApplicationControlBar> 
  
    <mx:Button label="Add" 
        enabled="{checkBox.selected}" 
        styleName="addButton" /> 
  
</mx:Application>