as3 倒计时实现

private var _timer:Timer;
private var _num:int = 1000;    //毫秒
private function stratTimer():void
{
     _timer =  new Timer(1000);
     _timer.addEventListener(TimerEvent.TIMER,timehandle,false,0,true);
     _timer.start();
}
   
private function timehandle(e:TimerEvent):void
{
    var count:int = _timer.currentCount;
    
    var str:String = timeTransform(_num,count);     //1000秒

    lbl.text = str;
}
   
//倒数计时
private function timeTransform(stattime:int,counter:int):String
{
    var str:String = "";
    var count:int = stattime - counter;
    var hour:int = Math.floor(count / 3600);
    var miniter:int = count % 3600 / 60;
    var second:int = count % 60;

    str = hour+":"+miniter+":"+second;
    return str;
}