as3自定义加载图片类

package
{
    import flash.display.Bitmap;
    import flash.display.Loader;
    import flash.display.Sprite;
    import flash.events.Event;
    import flash.events.ProgressEvent;
    import flash.net.URLRequest;
    /**
     * 图片加载类
     * @author sange
     */
    public class ImageLoader extends Sprite
    {
        private var loader:Loader;        
        private var sw:Number;
        private var sh:Number;
        
        /**
         * 构造函数
         * @param    w  图片width
         * @param    h  图片height
         * @param    url  图片地址
         */
        public function ImageLoader(w:Number,h:Number,url:String) 
        {            
            this.sw = w;
            this.sh = h;
            loader = new Loader();            
            loader.load(new URLRequest(url));
            loader.contentLoaderInfo.addEventListener(ProgressEvent.PROGRESS, loaderProgressHandler);
            loader.contentLoaderInfo.addEventListener(Event.COMPLETE, loaderCompleteHandler);
        }        
        
        /**
         * 加载进度 监听器
         * @param    e
         */
        private function loaderProgressHandler(e:ProgressEvent):void
        {
            var num:uint = (e.bytesLoaded / e.bytesTotal) * 100;
            trace(num+"%");
        }
        
        /**
         * 加载完成 监听器
         * @param    e
         */
        private function loaderCompleteHandler(e:Event):void
        {
            var bitmap:Bitmap = e.currentTarget.content as Bitmap;
            trace(bitmap);    
            bitmap.width = this.sw;
            bitmap.height = this.sh;        
            bitmap.x = 0;
            bitmap.y = 0;
            addChild(bitmap);
        }
    }
}