Understanding when and why to use different Android threads

Question

Hopefully someone can explain this to me or point me to a resource I can read to learn more. I am building an app that uses a ListView and a custom list adapter that I modeled off one of the many tutorials available online such as this one:

http://www.softwarepassion.com/android-series-custom-listview-items-and-adapters/

It worked fine. However, every example of how to do this runs the process of building the list of objects to be displayed and collecting the required data on separate threads.

I want to know why/couldn't you just put everything into onCreate? I can't see a reason why you would need separate threads to make this happen. Is there some general form/standard for when/what must me run on certain threads?

Answer 1

The Android docs on this are very good, as with most things.

The upshot is: the UI should always be responsive. So if you have some operation that will take enough time that the user will notice, you might want to consider not running it in the UI thread. Some common examples are network IO and database accesses. It's something of a case-by-case basis though, so you have to make the call for yourself a bit.