Why does my AsyncTask file download fail when trying to download a large file?

Question

I am trying to download a 600 MB file using an AsyncTask. If I execute my code on a real-world device, it works, but only if I "keep an eye on it" by not allowing the screen to remain off for any length of time, however, if I do not do this and just leave the device on its own, when I go to check on it a few minutes later, the progress dialog is gone and the file it has downloaded is only a fraction of the size it should be. My guess it that it has something to do with the phone putting WiFi to sleep after the screen's being off for a certain amount of time.

How do I fix this?

Here is the relevant code:

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();

            int lenghtOfFile = conexion.getContentLength();


            InputStream input = new BufferedInputStream(url.openStream());
            OutputStream output = new FileOutputStream("/sdcard/file.zip");

            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) {

         mProgressDialog.setProgress(Integer.parseInt(progress[0]));
    }

    @Override
    protected void onPostExecute(String unused) {
        dismissDialog(DIALOG_DOWNLOAD_PROGRESS);
    }
}
}

try to stick with existing implementation. The downloadManager exists to do stuff like this for you, effortlessly: http://developer.android.com/reference/android/app/DownloadManager.html — Ian, Aug 09 '11 at 14:52
API Level is too high, need more backward compatibility... thanks anyway though! — Frank Bozzo, Aug 09 '11 at 14:59

score 2 · Accepted Answer · edited May 23 '17 at 12:11

2

This question describes how to keep the screen on so the phone does not go to sleep. If you are trying to download files 600mb+, you might consider putting your application into some type of Service as this would potentially take a few hours.

edited May 23 '17 at 12:11

Community

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answered Aug 09 '11 at 14:49

Jack

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score 1 · Answer 2 · answered Aug 09 '11 at 14:53

1

Also you could use Download Manager if your target SDK is high enough.

answered Aug 09 '11 at 14:53

renam.antunes

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API Level is too high, need more backward compatibility... thanks anyway though! – Frank Bozzo Aug 09 '11 at 15:01

score 0 · Answer 3 · edited Jan 13 '13 at 19:56

0

Most likely you are using Wi-Fi connection, which can be disconnected as soon as screen is off. You can check this in:

Settings-> Wireless and Networks -> Wi-Fi Setting
Click , select Advanced
Click on "Wi-Fi sleep policy" and select "never".

But you should consider using Download Manager for newer devices (with Android 2.3+).

edited Jan 13 '13 at 19:56

Stephane Rolland

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answered Aug 09 '11 at 14:57

inazaruk

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Why does my AsyncTask file download fail when trying to download a large file?

3 Answers3