ComboBox中使用事件

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" creationComplete="initCB();">
    <mx:Script>
        <![CDATA[
            import mx.events.DropdownEvent;
            private function initCB():void{
                var info:Array = new Array();
                info.push({label:"红", data: "red"});
                info.push({label:"绿", data: "green"});
                info.push({label:"蓝", data: "blue"});
                _cb.dataProvider = info;
                
                _cb.addEventListener(DropdownEvent.CLOSE, chooseCB);
            }
            private function chooseCB(evt:DropdownEvent):void{
                var obj:Object = _cb.selectedItem;
                _tip.text = "label:" + obj.label + " data:" + obj.data;
            }
        ]]>
    </mx:Script>
    <mx:ComboBox x="62" y="51" id="_cb"></mx:ComboBox>
    <mx:TextArea x="62" y="81" height="114" id="_tip"/>
    
</mx:Application>