AS3在范围内拖动

import flash.geom.Rectangle;
var left:Number=sudutiao.x;
var top:Number=sudutiao.y;
var right:Number=sudutiao.width-sudukuai.width;
var botom:Number=sudutiao.height-sudukuai.height;
sudukuai.addEventListener(MouseEvent.MOUSE_DOWN,startdrag);
sudukuai.addEventListener(MouseEvent.MOUSE_UP,stopdrag);
function startdrag(event:MouseEvent):void {
 var rect:Rectangle=new Rectangle(left,top,right,botom);
 sudukuai.startDrag(false,rect);
}
function stopdrag(event:MouseEvent):void {
 sudukuai.stopDrag();
}