as3实现圆周运动效果_

代码如下：

package com{
import flash.display.Sprite;
import flash.events.Event;
public class RoundMove extends Sprite{
   private var r:Number=100; //圆周运动半径
   private var speed:Number=0.2; //圆周运动速度
   private var angle:Number=0;
   private var sp:Sprite;
   public function RoundMove(){
    init();
   }
   private function init():void{
    sp = new CircleSprite(20,0x0000ff,"");
    addChild(sp);
    sp.x=150;
    sp.y=150;
    addEventListener("enterFrame",roundMove); //开始运动
   }
   public function roundMove(e:Event):void{
    angle+=speed;
    sp.x=275+r*Math.cos(angle);
    sp.y=200+r*Math.sin(angle);
   }
}
}