AS3.0 下载队列类 帮助完成Flash队列下载

多次试验发现队列下载效率真的不太好。还是扩展一个Loader 加入了超时的设置，详细代码在跟帖中。
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前几天应征Flash程序员。被问到为什么Flash有时候Loader下载会无缘无故暂停，既不报超时也不报错。当时没想到为什么？后来被告知正确答案是FlashPlayer的并发下载的Bug。汗
今天自己作了一个队列下载的单例类。目的就是解决并发的问题和使用Loader的易用性。
原理是，生成了一个类的单例，在全局使用。单例中包括一个Timer时间轮训，一个array的下载URL列表，一个加载顺序的策略。很简单
如果感兴趣的朋友可以拿去用，哈哈。欢迎大家和我讨论。
CODE：
LoadLine.as
复制内容到剪贴板
代码:
package com.FSC.UI.InterActiveObject.DisplayObjectContainer.LoadLine
{
    import flash.display.MovieClip;
    import flash.display.Loader;
    import flash.net.URLRequest;
    import flash.utils.Timer;
    import flash.events.*;
    /**下载队列类
     * @ andy pan
     * @ v1.080506
     */
    public class LoadLine extends MovieClip
    {
        private static var loadLine:LoadLine;
        private static var key:Boolean=false;
        private var _loader:Loader= new Loader();
        private var _loaderList:Array = new Array();
        private var _timer:Timer = new Timer(500);
        private var _isNowLoading:Boolean=false;
        //加载失败尝试次数
        private var _tryErrorTime:Number=1;
        //当前加载失败次数
        private var _tryErrorNowTime:Number = 0;
        public function LoadLine()
        {
            if( !key ){
                throw new Error ("单例,请用 getInstance() 取实例。");
            }
            key=false;
            _timer.addEventListener(TimerEvent.TIMER,everySed);
            _timer.start();
            _loader.contentLoaderInfo.addEventListener(Event.COMPLETE,onCompleteHandler);
            _loader.contentLoaderInfo.addEventListener(IOErrorEvent.IO_ERROR, onError);
               _loader.contentLoaderInfo.addEventListener(SecurityErrorEvent.SECURITY_ERROR, onError);      
               _loader.contentLoaderInfo.addEventListener(ProgressEvent.PROGRESS, progressHandler);
        }
       
        public static function getInstance() : LoadLine {
            if ( loadLine == null ){
                 key=true;
                loadLine = new LoadLine();
            }
            return loadLine;
        }
       
        /**静态函数 下载命令
        * @param target下载地址
        */
        public function loadFile(target:URLRequest,emergent:Number=10){
            if(emergent==0){
                _loaderList.unshift(target);
                if(_isNowLoading){
                    //如果有正在加载的项目则 暂停
                    cancelNowLoad();
                }
            }else{
                _loaderList.push(target);
            }
        }
        /**终止当前下载
        */
        private  function cancelNowLoad(){
            _loader.close();
        }
        /**每秒监听 队列是否有下载
        * @param e 时间参数
        */
        private function everySed(e:TimerEvent){
            //但下载器空闲时
            if((!_isNowLoading)&&(_loaderList.length>0)){
                var tmp_url:URLRequest = _loaderList[0] as URLRequest;            
                _loader.load(tmp_url);
                this.addChild(_loader);
                _isNowLoading = true;
            }
        }
        /**当前下载中的侦听
        */
        private function progressHandler(e:ProgressEvent){
            this.dispatchEvent(new LoadLineProgressEvent(ProgressEvent.PROGRESS,_loaderList[0],false,false,e.bytesLoaded,e.bytesTotal));
        }
        /**当前下载完成
        */
        private function onCompleteHandler(e:Event){
            this.dispatchEvent(new LoadLineEvent(LoadLineEvent.ONLOADLINECOMPLETE,_loaderList[0],_loader.content));
            _loaderList.shift();//当完成下载后再从队列中删除
            _isNowLoading = false;
        }
        /**当加载错误进行尝试处理
        */
        private function onError(e:IOErrorEvent){
            _isNowLoading = false;
            if(_tryErrorNowTime>_tryErrorTime){
                trace("error:下载队列中有文件加载失败,并且超过尝试次数。已从队列中删除")
                this.dispatchEvent(new LoadLineEvent(LoadLineEvent.ONLOADLINECOMPLETE,_loaderList[0],false));
                _tryErrorNowTime=0;
                //当完成下载后再从队列中删除
                _loaderList.shift();
            }else{
                _tryErrorNowTime++;
            }
        }       
    }
}
自定义加载完成的事件类
LoadLineEvent.as
复制内容到剪贴板
代码:
package com.FSC.UI.InterActiveObject.DisplayObjectContainer.LoadLine
{
    import flash.events.Event;
    import flash.net.URLRequest;
    public class LoadLineEvent extends Event
    {
        public static var ONLOADLINECOMPLETE : String = "onLoadLineComplete";
        public var currentTragetURL:URLRequest;
        public var content:*;
        public var isSuccess:Boolean
        public function LoadLineEvent(type:String,URL:URLRequest,content,isSuccess:Boolean = true, bubbles:Boolean=true, cancelable:Boolean=false)
        {
            super(type, bubbles, cancelable);
            this.currentTragetURL = URL;
            this.isSuccess = isSuccess;
            this.content = content;
        }
       
    }
}
自定义加载过程中的事件类
LoadLineProgressEvent.as
复制内容到剪贴板
代码:
package com.FSC.UI.InterActiveObject.DisplayObjectContainer.LoadLine
{
    import flash.events.ProgressEvent;
    import flash.net.URLRequest;
    public class LoadLineProgressEvent extends ProgressEvent
    {
        public var currentTragetURL:URLRequest;
        public function LoadLineProgressEvent(type:String,URL:URLRequest, bubbles:Boolean=false, cancelable:Boolean=false, bytesLoaded:uint=0.0, bytesTotal:uint=0.0)
        {
            super(type, bubbles, cancelable, bytesLoaded, bytesTotal);
            this.currentTragetURL = URL;
        }
       
    }
}
使用方法如下：
import com.FSC.UI.InterActiveObject.DisplayObjectContainer.LoadLine.*;
var l:LoadLine = LoadLine.getInstance();
l.addEventListener(LoadLineEvent.ONLOADLINECOMPLETE,onComplete);
l.addEventListener(ProgressEvent.PROGRESS,onProgress);
//插入可用的url
l.loadFile(new URLRequest("http://static16.photo.sina.com.cn/bmiddle/54a5adcd44b992988febf"));
//插入错误的url
l.loadFile(new URLRequest("http://error.error.cn/error.htm"));
//插入可用的url
l.loadFile(new URLRequest("http://static3.photo.sina.com.cn/bmiddle/54a5adcd44b9926c6faf2"));
//插入可用的url 这里插入紧急级别为0（就是最高级别的）的URL 程序会停止当前下载过程，然后执行该下载
l.loadFile(new URLRequest("https://mail.google.com/mail/help/images/logo.gif"),0);

function onComplete(e:LoadLineEvent) {
       trace(e.currentTragetURL.url);
       if (e.isSuccess && e.currentTragetURL.url =="http://static16.photo.sina.com.cn/bmiddle/54a5adcd44b992988febf") {
              var bbb:* = e.content;
              bbb.y=0;
              addChild(bbb);
       }
}
function onProgress(event:LoadLineProgressEvent) {
       trace("progressHandler: bytesLoaded=" + event.bytesLoaded + " bytesTotal=" + event.bytesTotal);
}