onPostExecute on cancelled AsyncTask

android multithreading android-asynctask
hpique picture hpique · Jul 26, 2010 · Viewed 10.5k times · Source

Does onPostExecute execute if the AsyncTask has been cancelled?

If it does execute, is it safe to say that I should always ask if the task has been cancelled (isCancelled) at the start of onPostExecute, before doing anything else?

Answer

bain picture bain · Apr 30, 2013

The documented behaviour of onPostExecute on cancel() was changed between Android 2 and Android 4.

Android 2.3.7 onPostExecute :

Runs on the UI thread after doInBackground. The specified result is the value returned by doInBackground or null if the task was cancelled or an exception occured.

Android 4.0.1 onPostExecute :

Runs on the UI thread after doInBackground. The specified result is the value returned by doInBackground. This method won't be invoked if the task was cancelled.

So if you are still targeting Android 2 devices you should assume that onPostExecute will be called and in onPostExecute check for null result.

Related questions

Running multiple AsyncTasks at the same time -- not possible?

I'm trying to run two AsyncTasks at the same time. (Platform is Android 1.5, HTC Hero.) However, only the first gets executed. Here's a simple snippet to describe my problem: public class AndroidJunk extends Activity { class PrinterTask extends AsyncTask<String, …

Read More
Handler vs AsyncTask vs Thread

I got slightly confused about the differences between Handlers, AsyncTask and Threads in Android. I've read quite a few blogs and questions here in StackOverflow. Handler are background threads that provide you to communicate with the UI. Updating a progress …

Read More
Asynctask vs Thread in android

In UI, to perform some background work, I used a separate Thread. But as suggested by others, I am now using AsyncTask. What is the main difference between a Thread and an AsyncTask? In which scenario, should I use a …

Read More