onPostExecute not called after completion AsyncTask

Question

For some reason my onPostExecute() is not called after my AsyncTask finishes.

My class decleration:

public class setWallpaperForeground extends AsyncTask<String, Integer, Boolean>

My onPostExecute():

protected void onPostExecute(Boolean result)

Everything works fine, my doInBackground() completes successfully and returns a Boolean but then it just finishes.

Thanks

Answer 1

Did you create your AsyncTask on the UI thread? Also add an @Override annotaiton on your onPostExecute() method to make sure you declared it correctly.

Answer 2

Did you start the task with execute() method? The onPostExecute wouldn't run if you just invoke the doInBackground.

Answer 3

Found/Made another nasty mistake:

If your params of onPostExecute(Param param) don't match the one you defined with extends AsyncTask<...,...,Param> and you didn't use the @Override annotation, it will never be executed and you don't get a warning from Eclipse.

Note to myself: Just always use the @Override annotation and Eclipse will help you.

Another easy way to avoid all named mistakes:

in Eclipse: Right-click in code > Source > Override/Implement Methods

Answer 4

After having the same problem and none of these answers helped me, I found out that my UI thread was blocked (I used a CountDownLatch.await()) and therefore the onPostExecute() method that is supposed to be called by the UI thread was never called.

Answer 5

Made another nasty mistake that can result in this same error. When defining the AsyncTask and calling it, I was not calling execute but was calling doInBackground

new AsyncTask<String,Void,Void>() {
    ....
}.doInBackground("parameter");

rather than

new AsyncTask<String,Void,Void>() {
    ....
}.execute("parameter");

Answer 6

I have faced the same problem. None of the above solutions worked for me. Then i figured out the problem maybe it helps someone else .

In UI thread i call the following codes:

public class XActivity ...{
    onCreate(){
        ....

        new SaveDrawingAsync(this).execute();

        while(true)
        {
            if(MandalaActivity.saveOperationInProgress){
                continue;
            }
            super.onBackPressed();
            break;
        }

        ...
    }
}

My AsyncTask class definition :

public class SaveAsync extends AsyncTask<Object, Void, Void> {

    @Override
    public Void doInBackground(Object... params) {
        saveThem(); // long running operation
        return null;
    }

    @Override
    public void onPostExecute(Void param) {
        XActivity.saveOperationInProgress = false;
    }

    @Override
    public void onPreExecute() {
       XActivity.saveOperationInProgress = true;
    }

}

in the above code onPostExecute is not called. It is because of an infinite loop after asynctask execution . asynctask and inifinite loop both waits eachother to finish. Thus the code stucks!

The solution is changing the design!

Answer 7

I had the same behaviour, and the cause was that I have been posting a lot of messages as a progress inside doInBackground with following code:

new Handler(Looper.getMainLooper()).post(new Runnable() {
   @Override
   public void run() {
     // .. some UI updates
   }
});

this must have overloaded main thrad message queue, and caused long delay before onPostExecute would get called. The solution was to post only once every second.

Answer 8

For me it was user error. I was ending the AsyncTask by invoking cancel(true) on it and not reading the documentation closely enough to know that onPostExecute is not called in this case, onCancelled is.