下拉框树(treeComboBox)

树型的下拉框，在网上找到的

<?xml version="1.0" encoding="utf-8"?>
<mx:ComboBox  xmlns:mx="http://www.adobe.com/2006/mxml" creationComplete="initComponent()">
<mx:Script>
    <![CDATA[
           import mx.events.FlexEvent; 
           [Bindable] 
           private var _label:String; 
           [Bindable] 
           public var treeSelectedItem:Object;


           public function initComponent():void
           {
            
           }
           
           public function updateLabel(event:*):void{  
                    _label = event.currentTarget.selectedItem[this.labelField];     
                    treeSelectedItem = event.currentTarget.selectedItem; 
           } 
           
           override protected function updateDisplayList(unscaledWidth:Number,
                                                  unscaledHeight:Number):void
            {
                super.updateDisplayList(unscaledWidth, unscaledHeight);  
                
                if(dropdown && _label != null){   
                    text = _label; 
                } 
            }


             
    ]]>
</mx:Script>
    <mx:dropdownFactory>
      <mx:Component> 
        <mx:Tree creationComplete="initTree()" change="outerDocument.updateLabel(event)" showRoot="true" height="500" width="500">
         <mx:Script>
                <![CDATA[
                public function initTree():void {
                    var len:int=super.dataProvider.length;
                    for(var i:int;i<len;i++)
                    {
                       super.expandChildrenOf(super.dataProvider[i], true);
                    }
		    outerDocument.treeSelectedItem = super.dataProvider[0];/默认选中第一荐
                    super.selectedItem=outerDocument.treeSelectedItem;
                }
                ]]>
            </mx:Script>
        </mx:Tree>
     </mx:Component>
    </mx:dropdownFactory>
</mx:ComboBox>