AS3淡入淡出类

最近开始做FLEX开发，自己做了个淡入淡出效果类，留点痕迹。

调用方式：

   // 淡入
   var da:DisplayAlpha = new DisplayAlpha(pics,20,0.03);
   da.show();

package common
{
    import flash.display.DisplayObject;
    import flash.utils.setTimeout;
    
    // 淡入淡出
    public class DisplayAlpha
    {
        // 需要淡入淡出的对象
        private  var _obj:DisplayObject;
        // 设置时间间隔
        private  var _delay:Number;
        // 记录淡入淡出的方向
        private var _fx:int = 1;
        // 淡入淡出对象的最终alpha值
        private var _value:Number;
        // appha递增（递减）的幅度
        private var _alphaSpan:Number;
        
        public function DisplayAlpha(obj:DisplayObject,delay:Number,alphaSpan:Number=0.01)
        {
            _obj = obj;
            _delay = delay;
            if(_obj.alpha > 0)
            {
                _fx = -1;
            }
            _alphaSpan = alphaSpan;
        }
        
        // 淡出
        public  function hide():void
        {
            _obj.alpha -= _alphaSpan;
            if(_obj.alpha > 0)
            {
                setTimeout(hide,_delay);
            }
            else
            {
                _value = 0;
                setTimeout(setAlpha,500);
            }
        }
        
        // 淡入
        public  function show():void
        {
            _obj.alpha += _alphaSpan;
            if(_obj.alpha < 1)
            {
                setTimeout(show,_delay);
            }
            else
            {
                _value = 1;
                setTimeout(setAlpha,500);
            }
        }
        
        // 淡入淡出交替
        public function autoShowAndHide():void
        {
            _obj.alpha += _fx*_alphaSpan;
            if(_obj.alpha >= 1 || _obj.alpha <= 0)
            {
                _fx = -_fx;
            }
            setTimeout(autoShowAndHide,_delay);
        }
        
        // 给淡入淡出对象赋值
        private function setAlpha():void
        {
            _obj.alpha = _value;
        }
    }
}