Question

This should have an easy answer, yet I couldn’t find any.
And since I’m still an android dummy I came here to ask you people.

I’ve been making this project that executes 10 AsyncTasks on the startup.
Each task contains 3 URLs that collect data there and do nothing important in the app (yet).

I also have 10 textviews which I use to keep track of the progress of the AsyncTasks.

When a task starts the appropriate textview is put on “Start”
When a task is progressing it sets its appropriate textview to “Downloading”
When a task is finished it sets its appropriate textview to “Finished”

This is what I observed and came to question about the AsyncTask.
When I start the app I notice 5 of the textviews being switched to the “Downloading” marker, so I see 5 AsyncTasks doing their job as they should. When done it starts up a new AsyncTask. Yet they never reach over that limit of 5.

What causes this limit of 5 AsynchTasks running at the same time?
Did I cause this in some file which I cannot find?
Is this a limit of android 2.3.3? Maybe a limit of the device I’m using to sim the app?

Can anyone elaborate for me?

Answer 1

Yes, there’s a limit. AsyncTask is backed by a ThreadPoolExecutor with a core pool size of 5, but a maximum pool size of 128 (from 1.6 – 4.0.3), so really I would think you should see all 10 of yours run at once. You can’t change it though. If you really want to do something different (and I wouldn’t recommend it unless you have a very specific reason), you’ll have to do something custom with a larger pool size or just spin up a bunch of threads manually.

Update:

Here’s what the docs say:

If there are more than corePoolSize but less than maximumPoolSize threads running, a new thread will be created only if the queue is full.

So that’s why. Your queue isn’t full, so it just keeps it at the core pool size.