android threads: stopping a thread with heavy computation

Question

I am doing some heavy computation in my android application. Since i dont want to block the UI-thread, I do the computation in a seperate WorkerThread, which extends Thread. This works fine. But i have trouble stopping the thread. The normal way to stop a thread is either using interrupt() oder a volatile variable to tell the thread, that it should end. But this works only in Threads with some kind of loop. I am doing computation in the thread by using external libraries and I cannot put the isInterrupted()-check into this library. The bad way to stop a thread is using the stop()-Methode, which is deprecated, but in my case the right way, since the thread manipulates only internal values. Unfortunatly Android doesnt support stop(), since it doesn't support deprecated thread methods.

10-18 10:26:39.382: ERROR/global(13919): Deprecated Thread methods are not supported.
10-18 10:26:39.382: ERROR/global(13919): java.lang.UnsupportedOperationException

Do you now any other method to stop a thread in android? Thanks in advance! Tobias

PS: some code to show the problem:

public void method()
{
    WorkerThread t = new WorkerThread();
    t.start();
    synchronized (this)
    {
        try
        {
            wait(1000);
        } catch (InterruptedException e)
        {
            Log.e("",e.toString(),e);
        }    
    }

    //t.stop(); //not supported in android
    //t.interrupt(); //can not be checked by the thread    
}

class WorkerThread extends Thread
{
    public void run()
    {
        externalLibrary.heavyComputation();
    }
}

score 0 · Answer 1 · answered Jul 02 '11 at 07:27

0

Look at AsyncTask. It is more proper and far more comfortable way to implement background tasks. As you can read in documentation:

 private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> {
     protected Long doInBackground(URL... urls) {
         int count = urls.length;
         long totalSize = 0;
         for (int i = 0; i < count; i++) {
             totalSize += Downloader.downloadFile(urls[i]);
             publishProgress((int) ((i / (float) count) * 100));
         }
         return totalSize;
     }

     protected void onProgressUpdate(Integer... progress) {
         setProgressPercent(progress[0]);
     }

     protected void onPostExecute(Long result) {
         showDialog("Downloaded " + result + " bytes");
     }
 }

answered Jul 02 '11 at 07:27

piotrpo

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I don't see any possibility to stop the execution of an asynctask. – Tobias Jul 02 '11 at 07:38
It looks like this may work. This class has a cancel() method that looks like it (theoretically) does what you want it to do. – Zéychin Jul 02 '11 at 07:40
@Zeychin `cancel()` will attempt to interrupt the task but it will not magically stop code that is not responding to interrupts. – Alex Gitelman Jul 02 '11 at 07:43
I figured as much, but the top-level documentation didn't seem to indicate that as I skimmed over it. I figured that I would point it out, just in case. – Zéychin Jul 02 '11 at 07:52
@Tobias - as far as I understood you need to make extensive calculations and get result. In my opinion AsyncTask is best way to implement such feature. Why do you have a need to interupt thread? – piotrpo Jul 02 '11 at 08:51

score 0 · Accepted Answer · answered Jul 02 '11 at 07:47

0

Generally, unless your external library provides some protocol to stop computation there is no way to stop it gracefully. Many well written libraries will do provide such protocol, so look at its api. Also it may respect interrupt() call. May be you already checked it but it may also take some time before it exits.

answered Jul 02 '11 at 07:47

Alex Gitelman

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7
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This seems to be right. I haven't found any possibility. Thanks! – Tobias Jul 02 '11 at 20:04

android threads: stopping a thread with heavy computation

2 Answers2