Android AsyncTask.THREAD_POOL_EXECUTOR vs custom ThreadPool with Runnables

Question

I have some tasks that I need to process concurrently on Android and I would like to use some sort of a thread pool to do so. I couldn't find in the documentation what actually happens "behind the scenes" when executing an AsyncTask with AsyncTask.THREAD_POOL_EXECUTOR.

My question is: What do I lose by using AsyncTasks with AsyncTask.THREAD_POOL_EXECUTOR as opposed to implementing a custom ThreadPool with Runnables? (Let's talk post-honeycomb).

I realize the question is rather general, but I'm fairly new to doing concurrent programming (besides AsyncTask itself). I'm not looking for a tutorial on concurrent programming! I only seek to understand how the Android specific AsyncTask.THREAD_POOL_EXECUTOR is different. I think an explanation would be helpful for others in the future as they weigh the pros and cons of choosing to use AsyncTask vs Thread/Runnable. Thanks in advance!

Answer 1

AsyncTasks provide you with possibility to execute actions on UI thread before and after executing worker task. So, if you dont need communicating with UI then use your own executor - you can always implement this using handler. AsyncTasks are being executed serially since api 11 because parallel execution was considered to difficult to properly implement.

If you need more flexibility, then executors are a way to go, they will allow you to freely specify how many tasks to execute in parallel, how many to put in queue etc.

If you are interested in details, you can always look into sources:

http://androidxref.com/4.4.3_r1.1/xref/development/samples/training/bitmapfun/BitmapFun/src/main/java/com/example/android/bitmapfun/util/AsyncTask.java