Android SDK AsyncTask doInBackground not running (subclass)

Solution 1:

You should checkout this answer: https://stackoverflow.com/a/10406894/347565 and the link to google groups it includes.

I had a similar problem as you, still unclear why it is not working, but I changed my code like this and problem is gone:

ASyncTask<Void,Void,Void> my_task = new ASyncTask<Void,Void,Void>() { ... };
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB)
    my_task.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, (Void[])null);
else
    my_task.execute((Void[])null);

Solution 2:

Matthieu's solution will work fine for most, but some can face problem; unless digging in many links provided here or from web, like Anders Göransson's explanation. I am trying to summarize some other reads right here and quickly explain solution if executeOnExecutor is still working in single thread...

Behavior of AsyncTask().execute(); has changed through Android versions. Before Donut (Android:1.6 API:4) tasks were executed serially, from Donut to Gingerbread (Android:2.3 API:9) tasks executed paralleled; since Honeycomb (Android:3.0 API:11) execution was switched back to sequential; a new method AsyncTask().executeOnExecutor(Executor) however, was added for parallel execution.

In sequential processing all Async tasks run in a single thread and thus have to wait before the previous task ends. If you need to execute code immediately, you need tasks to be processed in parallel in separate threads.

With AsyncTask serial execution is not available between Donut and Honeycomb versions, while parallel execution is not available before Donut.

For parallel processing after Donut: Check the Build version and based on that use .execute() or .executeOnExecutor() method. Following code can help...

AsyncTask<Void,Void,Void> myTask = new AsyncTask<Void,Void,Void>() { ... }; // ... your AsyncTask code goes here
if (Build.VERSION.SDK_INT>=Build.VERSION_CODES.HONEYCOMB)
    myTask.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
else
    myTask.execute();

NOTE: Function .executeOnExecutor() has checks if targetSdkVersion of project is less than or equal to HONEYCOMB_MR1 (Android:2.1 API:7) then it forces the executor to be THREAD_POOL_EXECUTOR (which runs Tasks sequentially in post Honeycomb).
If you have not defined a targetSdkVersion then minSdkVersion is automatically considered to be the targetSdkVersion.
Hence for running your AsyncTask in parallel on post Honeycomb you cannot leave targetSdkVersion empty.