Flash AS3-URLLoader再次加载最后一个数据

Question

好吧，这里有一个奇怪的错误。。。

在我的应用程序中，我加载了多个xml文件。为了加载这些，我总是创建一个新的URLLoader。没什么特别的。

第一个文件运行良好，第二个文件也运行良好。然而，第三个文件报告加载良好，但它所包含的数据实际上是第二个文件的数据。当前的解决方法是两次加载第三个文件，这在某种程度上起作用。。。奇怪的

我完全不知道这样的事情怎么会发生。当然，这三个文件都是具有不同路径的不同文件。

这是相关的类，希望它有任何用处，如果有什么不清楚的地方，请询问。DownloadJob类只是一个包含String和Function对象的辅助类。下载完成后会调用后一个。

    // Actual class stuff
    private var _downloadQueue  :Array = new Array();
    /**
     * Adds a download to the queue. Will be started immediatly.
     * @param   p_url       The URL of the download.
     * @param   p_callback  The function to call when the download is finished. Has to take a DisplayObject/Sound/String as first parameter.
     */
    public function addDownload(p_url:String, p_callback:Function) :void
    {
        var job :DownloadJob = new DownloadJob(p_url, p_callback);
        _downloadQueue.push(job);
        debug.ttrace("added: " + job.url);
        // If it is the only item, start downloading
        if (_downloadQueue.length == 1)
        {
            var job :DownloadJob = DownloadJob(_downloadQueue[0]);
            load(job);
        }
    }
    /**
     * Will call the callback and dispatch an event if all loading is done.
     * @param   p_event The event that is passed when a download was completed.
     */
    private function downloadComplete(p_event:Event) :void 
    {
        var job :DownloadJob = DownloadJob(_downloadQueue[0]);
        var downloaded :Object = p_event.target;
        _downloadQueue.splice(0, 1);
        debug.ttrace("completed: " + job.url);
        // Notify via callback
        if (downloaded is LoaderInfo)
        {
            job.callback(downloaded.content);
        }
        else if (downloaded is Sound)
        {
            job.callback(downloaded);
        }
        else if (downloaded is URLLoader)
        {
            // This one holds the data of the previously loaded xml, somehow
            job.callback(URLLoader(downloaded).data);
        }
        // Continue downloading if anything is left in the queue
        if (_downloadQueue.length > 0)
        {
            var job :DownloadJob = DownloadJob(_downloadQueue[0]);
            load(job);
        }
        else
        {
            dispatchEvent(new Event(EVENT_DOWNLOADS_FINISHED));
        }
    }
    /**
     * Will load the passed job immediatly.
     * @param   p_job   The job to load.
     */
    private function load(p_job:DownloadJob) :void
    {
        // Different loaders needed for data, sound and non-sound
        if (p_job.url.indexOf(".xml") != -1 ||
            p_job.url.indexOf(".txt") != -1)
        {
            var urlloader :URLLoader = new URLLoader();
            urlloader.addEventListener(Event.COMPLETE, downloadComplete);
            urlloader.addEventListener(IOErrorEvent.IO_ERROR, handleError);
            urlloader.load(new URLRequest(p_job.url));
        }
        else if (   p_job.url.indexOf(".mp3") != -1 &&
                    p_job.url.indexOf(".flv") != -1)
        {
            var sound :Sound = new Sound();
            sound.addEventListener(Event.COMPLETE, downloadComplete);
            sound.addEventListener(IOErrorEvent.IO_ERROR, handleError);
            sound.load(new URLRequest(p_job.url));
        }
        else
        {
            var loader :Loader = new Loader();
            loader.contentLoaderInfo.addEventListener(Event.COMPLETE, downloadComplete);
            loader.contentLoaderInfo.addEventListener(IOErrorEvent.IO_ERROR, handleError);
            loader.load(new URLRequest(p_job.url));
        }
    }
}

Answer 1

我在你的类上花了一些时间，但找不到任何错误，即使是从计时器中随机调度addDownload命令时也是如此——一切都如预期，没有混乱，没有奇怪的数据残留。我只能猜测，这个问题可能与ActionScript中奇怪的变量处理有关，如果它真的在你发布的代码中的话。

所以，我冒昧地重新安排了你们的班级：

• 我将队列的类型更改为Vector.<DownloadJob>。这让我们摆脱了所有的类型铸造
• 当前下载存储在字段变量currentJob中。无论如何，一次只能做一份工作。这就消除了所有的函数参数
• 如果currentJob不是null，即实际正在进行下载，则只会将作业添加到队列中。如果不需要等待的话，我们不必排队。这只留下对每个push()和splice()的单个调用。在添加和删除内容方面不再存在不确定性
• 删除了匈牙利符号（我们在ActionScript中没有这样做）
• 将较大的方法拆分为更小、更可读的块（帮助我思考：）
• 删除了所有注释，除了API方法（我认为代码应该不言自明）

请尝试与您以前的类交换下面的代码，看看问题是否仍然存在。如果是这样，我确信问题存在于加载程序之外，可能存在于处理有效负载的回调函数中。

private static const EVENT_DOWNLOADS_FINISHED : String = "EVENT_DOWNLOADS_FINISHED";
private var currentJob : DownloadJob;
private var downloadQueue : Vector.<DownloadJob> = new Vector.<DownloadJob> ();
/**
 * Adds a download to the queue. Will be started immediatly.
 * @param   url       The URL of the download.
 * @param   callback  The function to call when the download is finished. Has to take a DisplayObject/Sound/String as first parameter.
 */
 public function addDownload ( url : String, callback : Function ) : void {
    var job : DownloadJob = new DownloadJob ( url, callback );
    if (currentJob) downloadQueue.push ( job );
    else {
        currentJob = job;
        load ();
    }
}
private function load () : void {
    if ( jobIsText () ) loadText ();
    else if ( jobIsSound () ) loadSound ();
}
private function jobIsText () : Boolean {
    var url : String = currentJob.url;
    return url.indexOf ( ".xml" ) != -1 || url.indexOf ( ".txt" ) != -1;
}
private function jobIsSound () : Boolean {
    var url : String = currentJob.url;
    return url.indexOf ( ".mp3" ) != -1;
}
private function loadText () : void {
    var urlloader : URLLoader = new URLLoader ();
    urlloader.addEventListener ( Event.COMPLETE, handleComplete );
    urlloader.addEventListener ( IOErrorEvent.IO_ERROR, handleError );
    urlloader.load ( new URLRequest ( currentJob.url ) );
}
private function loadSound () : void {
    var sound : Sound = new Sound ();
    sound.addEventListener ( Event.COMPLETE, handleComplete );
    sound.addEventListener ( IOErrorEvent.IO_ERROR, handleError );
    sound.load ( new URLRequest ( currentJob.url ) );
}
private function handleComplete ( ev : Event ) : void {
    processPayload ( ev.target );
    if (downloadQueue.length > 0) loadNext ();
    else dispatchEvent ( new Event ( EVENT_DOWNLOADS_FINISHED ) );
}
private function handleError ( ev : Event ) : void {
    trace ( "Error while downloading:" + currentJob.url );
}
private function processPayload ( loader : Object ) : void {
    currentJob.callback ( getPayload ( loader ) );
    currentJob = null;
}
private function loadNext () : void {
    currentJob = downloadQueue.splice ( 0, 1 )[0];
    load ();
}
private function getPayload ( loader : Object ) : Object {
    return (loader is LoaderInfo) ? loader.content :     
               (loader is URLLoader) ? URLLoader ( loader ).data :
                   loader;
}