如何在AsyncTask中取回任务完成状态 [英] How to get back the task completion status in AsyncTask

问题描述

这与我之前的帖子有关 使用 AsyncTask 下载多个文件的问题

This is related to my previous post Problem with downloading multiple files using AsyncTask

我正在尝试下载两个视频文件并在此过程中显示一个 ProgressDialog.为此，我正在使用 AsyncTask.我希望第一次下载完成，释放内存然后开始第二次下载.我编写了以下代码来实现这一点，但似乎第二次下载从未开始.

I'm trying to download two video files and also show a ProgressDialog during the process. For this I'm using AsyncTask. I want the 1st download to complete, free up memory then start the 2nd download. I wrote the following code to achieve this, but it seems the 2nd download never begins.

startDownload() {
   DownloadFileAsync d1 = new DownloadFileAsync();
   d1.execute(videoPath+fileNames[0],fileNames[0]);

   if(d1.getStatus()==AsyncTask.Status.FINISHED) {
     d1 = null;
     DownloadFileAsync d2 = new DownloadFileAsync();
     d2.execute(videoPath+fileNames[1],fileNames[1]);
   }
}

有什么办法可以让我找回第一个任务的完成状态&然后开始第二个?

Is there a way that I can get back the completion status of my 1st task & then start the 2nd ?

以下是我的 DownloadFileAsync 类的代码:

The following is the code of my DownloadFileAsync class:

class DownloadFileAsync extends AsyncTask<String, String, String> {

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        showDialog(DIALOG_DOWNLOAD_PROGRESS);
    }

    @Override
    protected String doInBackground(String... aurl) {
        int count;

        try {
            URL url = new URL(aurl[0]);
            URLConnection conexion = url.openConnection();
            conexion.connect();

            File root = android.os.Environment.getExternalStorageDirectory();

            int lenghtOfFile = conexion.getContentLength();
            Log.d("ANDRO_ASYNC", "Lenght of file: " + lenghtOfFile);

            InputStream input = new BufferedInputStream(url.openStream());
            OutputStream output = new FileOutputStream(root.getAbsolutePath() + "/videos/" + aurl[1]);

            byte data[] = new byte[1024];

            long total = 0;

            while ((count = input.read(data)) != -1) {
                total += count;
                publishProgress(""+(int)((total*100)/lenghtOfFile));
                output.write(data, 0, count);                    
            }
            output.flush();
            output.close();                
            input.close();

        } catch (Exception e) {}
        return null;

    }
    protected void onProgressUpdate(String... progress) {
         Log.d("ANDRO_ASYNC",progress[0]);
         mProgressDialog.setProgress(Integer.parseInt(progress[0]));
    }

    @Override
    protected void onPostExecute(String unused) {
        dismissDialog(DIALOG_DOWNLOAD_PROGRESS);
        tv.append("

File Download Completed!");
        sendBroadcast(new Intent(Intent.ACTION_MEDIA_MOUNTED, Uri.parse("file://"+ Environment.getExternalStorageDirectory())));            
    }
}

推荐答案

正如 DKIT Android 所建议的，您可以从 onPostExecute 开始第二次下载，但前提是例如 download2 为 null

As DKIT Android suggested, you could start the second download from onPostExecute, but only if for example download2 is null

@Override
protected void onPostExecute(String unused) 
{

   if (d2 == null)
   {
       d2 = new DownloadFileAsync();
       d2.execute(videoPath+fileNames[1],fileNames[1]);    
   }    
}

如果您需要启动更多下载，只需在 asynctask 之外编写该方法，它将检查接下来应该启动哪个下载.

If you need to start more downloads, just write the method outside of your asynctask, which will check which download should be started next.

这篇关于如何在AsyncTask中取回任务完成状态的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！