플렉스 어떤버튼인지 찾아서 포커스 주기

어떤 버튼인지 String 서칭후 포커스 주는 소스입니다.

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
layout="absolute" backgroundColor="white">

     <mx:Script>
     <![CDATA[

		public function focusa():void { 
			var str:String = "button2";                        
		    focus(str);                 
		}	 
		
		public function focus(object:String):void {
			var obj:Button = this[object] as Button;                          
		    obj.setFocus();      
		    obj.dispatchEvent(new MouseEvent(MouseEvent.ROLL_OVER));           
		}

    ]]>
    </mx:Script>
    
    <mx:Button label="main" id="main" click="focusa()" x="139" y="42"/> 
    <mx:Button label="1" id="button1"  x="249" y="82"/>
    <mx:Button label="2" id="button2" x="201" y="82"/>
    <mx:Button label="3" id="button3" x="153" y="82"/>
    <mx:Button label="4" id="button4"  x="105" y="82"/>
    <mx:Button label="5" id="button5"  x="57" y="82"/>

</mx:Application>

--- 결과물