as3鼠标控制人物移动

var speed:uint=5;
var mx
var my
var angle=0
var hero;
stage.addEventListener(MouseEvent.MOUSE_DOWN,onmousedown);
function onmousedown(e:MouseEvent):void{
 mx=mouseX;
 my=mouseY
 hero.addEventListener(Event.ENTER_FRAME,onenterframe);
}
function onenterframe(e:Event):void{
 hero=e.target as Sprite;
 angle = Math.atan2(my-hero.y, mx-hero.x);
 if(hero.x!=mx){
  if(Math.abs(mx-hero.x)>Math.abs(speed*Math.cos(angle))){
   hero.x+=speed*Math.cos(angle);
  }
 }
 if(hero.y!=my){
  if(Math.abs(my-hero.y)>Math.abs(speed*Math.sin(angle))){
   hero.y+=speed*Math.sin(angle);
  }
 }
 if (mx == hero.x && my == hero.y) {  
  hero.removeEventListener(Event.ENTER_FRAME,onenterframe);
  }
}