[flexcoders] Drawing the background Issue

[j2me_soul]

The code is pretty simple. This is all I am trying to do: 
 <mx:Script>
  <![CDATA[
   private function init():void{
//    var p:Point = new Point(btn1.x, btn1.y);
//    var pg:Point = localToGlobal(p);
    
    with(btn1.graphics){
     clear();
     lineStyle(2, 0xffffff, 1);
     beginFill(0x123456, 1);
//     globel coordinates doesn't work too
//     drawRect(pg.x, pg.y, btn1.width + 20, btn1.height+ 20);
     drawRect(btn1.x, btn1.y, btn1.width + 20, btn1.height+ 20);
     endFill();
    }
    
     btn2.graphics.clear();
     btn2.graphics.lineStyle(2, 0xffffff, 1);
     btn2.graphics.beginFill(0x123456, 1);
     btn2.graphics.drawRect(btn2.x, btn2.y, btn2.width + 20, btn2.height+ 20);
     btn2.graphics.endFill();
   }
  ]]>
 </mx:Script>
 <mx:Button id="btn1" label="ButtonOne"  x="149" y="198"/>
 <mx:Button id="btn2" label="ButtonTwo"  x="273" y="198"/>
The problem is that the background was drawn in a very far away.
I am wondering why the backgroundcolor depart from the buttons.