How to elevate the priority of AsyncTask?

Question

Is there a way to elevate the priority of an AsyncTask?

I'm doing some image manipulation in an AsyncTask. On a very slow device, it takes up to 60 seconds to process an image. Now I'd like to increase the performance by elevating the priority of the task. Can it be done somehow?

You want to elevate the priority. Do you have multiple async tasks running at the same time? — Ankit Aggarwal, Feb 03 '16 at 07:14

score 13 · Accepted Answer · answered Feb 03 '16 at 07:31

13

Try to use following (increase of priority AsyncTask threads):

protected final MyResult doInBackground(MyInput... myInput) {
    Process.setThreadPriority(THREAD_PRIORITY_BACKGROUND + THREAD_PRIORITY_MORE_FAVORABLE);
    // blah-blah
}

answered Feb 03 '16 at 07:31

Barmaley

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why do you add `final` to this method? – user25 May 26 '18 at 19:03
Can not resolve method "setThreadPriority(int)", what should I do? – Fahad Maqsood Qazi Jul 30 '20 at 06:18

score 8 · Answer 2 · edited Jun 20 '20 at 09:12

If you do not have a heavy UI which would interleave with the AsyncTask flow of execution, then your problem is in the algorithm used.

If you can divide your algorithm in parallel tasks, then you can use a pool of executors. If not, your Async Task is just doing serial work.

Be aware that according to AsyncTask:

When first introduced, AsyncTasks were executed serially on a single background thread. Starting with DONUT, this was changed to a pool of threads allowing multiple tasks to operate in parallel. Starting with HONEYCOMB, tasks are executed on a single thread to avoid common application errors caused by parallel execution.

If you truly want parallel execution, you can invoke executeOnExecutor(java.util.concurrent.Executor, Object[]) with THREAD_POOL_EXECUTOR

You can use code like this on most devices

if (Build.VERSION.SDK_INT >= 11) {
    asyncTask.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
} else {
    asyncTask.execute();
}

or even create a custom ThreadPoolExecutor.

it doesn't change thread priority!! though it helps to run `doInBackground` method faster, for changing Thread priority see the accepted answer... so `executeOnExecutor` is only for fixing delay before thread starts https://stackoverflow.com/questions/12404668/asynctasks-doinbackground-starts-its-execution-too-late-after-asynctaskexecut — user25, May 26 '18 at 21:29

score 2 · Answer 3 · answered Oct 22 '20 at 08:44

Set thread priority inside your AsyncTask doInBackground:

Thread.currentThread().setPriority(Thread.MAX_PRIORITY);

Like following:

protected Object doInBackground(Integer... params) {
    Thread.currentThread().setPriority(Thread.MAX_PRIORITY);
    ...
    ...
}

How to elevate the priority of AsyncTask?

3 Answers3