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Editorial Team
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Asked: 2026-06-03T06:35:55+00:00

Why can an AsyncTask perform only one job? For example, task = new SubAsyncTask(…);

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Why can an AsyncTask perform only one job? For example, 

task = new SubAsyncTask(...); // assume the parameter is correct.
task.execute(...) //
task.execute(...)// calling once again, it throws exeception.

But a Handler can continously perform more than one task:

hd = new Handler(...); // assume the parameter is correct
hd.sendMessage(...); //
hd.sendMessage(...);// no exeception is thrown.

Is an AasyncTask object for a one-time job only? If I don’t want to create multiple object for similar task, should I choose Handler?

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1 Answer

  1. Editorial Team

    Handler and AsyncTasks are way to implement multithreading with UI/Event Thread.

    Handler allows to add messages to the thread which creates it and It also enables you to schedule some runnable to execute at some time in future.

    Async task enables you to implement MultiThreading without get Hands dirty into threads. Async Task provides some methods which need to be defined to get your code works. in onPreExecute you can define code, which need to be executed before background processing starts. doInBackground have code which needs to be executed in background, in doInBackground we can send results to multiple times to event thread by publishProgress() method, to notify background processing has been completed we can return results simply. onProgressUpdate() method receives progress updates from doInBackground method, which is published via publishProgress method, and this method can use this progress update to update event thread, onPostExecute() method handles results returned by doInBackground method.

    So, you dont need to call execute method on AsyncTask multiple TImes, instead you can invoke publishProgress.

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