AsyncTask does not updating my textview in resume fragment after destroy

Question

I am running a thread in background contains timer and I display this timer in TextView but when I change current fragment and I return the timer still running in logcat but does not update in UI

My code:

final Runnable r = new Runnable() {
            public void run() {
                if (mBound) {
                    long elapsedTime = stopWatchService.getElapsedTime();
                    formattedTime = DateUtils.formatElapsedTime(elapsedTime);
                    Log.i(TAG, "formattedTime "+ formattedTime);
                    textView.setText(formattedTime);
                }
            }
        };
 Task task = new Task(r);
 task.execute((Void) null);

My task:

public class Task extends AsyncTask<Void, Void, Void> {


        private static final String TAG = "Task";

        private boolean mPaused;

        private Runnable mRunnable;

        public Task(Runnable runnable, TextView textView) {
            mRunnable = runnable;
            play();


        }

        @Override
        protected Void doInBackground(Void... params) {
            while (!isCancelled()) {
                if (!mPaused) {

                    mRunnable.run();
                    sleep();
                }
            }
            return null;
        }

        private void sleep() {
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                Log.w(TAG, e.getMessage());
            }
        }

        public void play() {
            mPaused = false;
        }

        public void pause() {
            mPaused = true;
        }

        public void stop() {
            pause();
            cancel(true);
        }

        public boolean isPaused() {
            return mPaused;
        }
}

My service:

public class StopWatchService extends Service {

    private String TAG = "walkingApp";
    StopWatch stopWatch = new StopWatch();

    public StopWatchService() {

    }

    public class LocalBinder extends Binder {
        public StopWatchService getService() {
            return StopWatchService.this;
        }
    }

    private final IBinder mBinder = new LocalBinder();


    public IBinder onBind(Intent intent) {
        return mBinder;
    }

    /*
    When the service is started, start stopwatch.
     */
    public int onStartCommand(Intent intent, int flags, int startId) {
        stopWatch.start();


        return START_STICKY;
    }

    /* return how much time has passed in seconds */
    public long getElapsedTime() {
        return stopWatch.getElapsedTime();
    }


    @Override
    public boolean stopService(Intent name) {
        stopWatch.stop();
        return super.stopService(name);

    }

    @Override
    public void onDestroy() {
        super.onDestroy();
       // stopWatch.stop();
    }
}

Sorry, but what is your question, you want the AsynTask to keep running even if you leave the fragment ? — Mouaad Abdelghafour AITALI, Dec 17 '22 at 21:56
When the fragment is destroyed, the `AsyncTask` will continue to run and try to update the `TextView`, but the `TextView` may not be available anymore because the fragment has been destroyed. — Mouaad Abdelghafour AITALI, Dec 17 '22 at 21:58
can you please explain more, what exactly you want to achieve, I can help you. — Mouaad Abdelghafour AITALI, Dec 18 '22 at 10:08
I want to synchronize TextView in resume after the fragment has been destroyed — No zha, Dec 18 '22 at 10:40
For example, your TextView shows a counter and when you leave the fragment the counter gets initialized to 0? You want to continue from where the counter stopped before leaving the fragment, right ? — Mouaad Abdelghafour AITALI, Dec 20 '22 at 17:11
yes my textView get initialized to 0 my in the runnable the value of counter still right — No zha, Dec 22 '22 at 16:08
Share with me your `Task` class also what is `stopWatchService.getElapsedTime()`, I would like to run your code, but it's missing these value — Mouaad Abdelghafour AITALI, Dec 22 '22 at 16:35
I didn't run your code because it's still missing StopWatch class, however, try to replace `textView.setText(formattedTime);` with `getActivity().runOnUiThread(() -> textView.setText(formattedTime));` — Mouaad Abdelghafour AITALI, Dec 22 '22 at 17:07

score 1 · Answer 1 · answered Dec 17 '22 at 20:00

1

AsyncTask was deprecated a few years ago, which was, IMHO, long overdue. It had lots of problems, like the one you are encountering, and only really ever worked well in some very special cases.

There are several other ways to handle this situation, including, but not limited to RxJs, executors, and Kotlin Coroutines.

Have a look at The AsyncTask API is deprecated in Android 11. What are the alternatives?

answered Dec 17 '22 at 20:00

GreyBeardedGeek

29,460
2
47
67

I want to synchronize TextView in resume after the fragment has been destroyed – – No zha Dec 20 '22 at 15:52

score 0 · Answer 2 · answered Dec 22 '22 at 17:23

The short answer here is probably that you use a Chronometer instead of a TextView. Then all you need to do is set the start time once, and the you no longer need to worry about keeping track of what time to display yourself. You can get rid of your timer. For example (very naive approach):

public class MyActivityOrFragment ... {

  //Start time as "uptime"
  private static final AtomicLong base = 
    new AtomicLong(SystemClock.uptimeMillis());

  @Override
  public void onStart() {
    //...
    chronometer.setBase(base.get());
  }

}

If you want to change this base time whilst the Activity/Fragment is open, then you can get do it in plenty of ways. You could send an intent with the base time as an extra, use an interface, an event bus, monitor a database, etc.

AsyncTask does not updating my textview in resume fragment after destroy

2 Answers2