Android - SQLite ContentResolver insert/delete/update on UI Thread?

Question

I have looked through many examples/tutorials of using SQLite in Android. Let's say you have an app that uses SQLite, ContentProvider, CursorLoader, a custom CursorAdapter. Now all major examples of this that I've found rely on a CursorLoader to fetch data to the CursorAdapter, which by the nature of CursorLoader happens in an Async - UI thread safe manner. However, these same examples all make insert/delete/update calls through the ContentResolver on the main thread (e.g. from onClick, onResume, onPause). (Example) They don't wrap these calls in an AsyncTask or launch a separate thread or use the AsyncQueryHandler. Why is this, how can so many well written blogs/examples make such an obvious mistake? Or are simple single row insert/delete/update calls so quick that they are safe enough to launch from the Main/UI thread? What is the proper way to do these quick calls?

Answer 1

I also got confused about the samples making calls on the main thread. I guess the samples just simplified the demonstrations avoiding extra threads and callbacks, since single insert/update/delete call may return quickly.

Besides the Loader pattern for query, android did provide a helper class AsyncQueryHandler, since API level 1, for async CRUD operations with full CRUD callbacks supported. The AsyncQueryHandler works inside with a HandlerThread for the async operations and delivers the results back to the main thread.

So I do believe the ContentProvider queries should run in worker threads other than the UI, and those samples may not be best practices according to the official design.

=== edit

Found an annotation from the official framework docs, see this or this, Line 255:

In practice, this should be done in an asynchronous thread instead of
on the main thread. For more discussion, see Loaders. If you are not
just reading data but modifying it, see {@link android.content.AsyncQueryHandler}.

=== edit 2 Link to actual android dev guide containing the above quote

Answer 2

This question has been on my mind since a long time. I guess, this depends on the complexity of the file we are trying to Insert, Update or Delete. If our application is going to Insert or Update large files, it would be always right to do it asynchronously and if the files aren't going to be that big, running it on UI thread can be done.

However, it is always recommended to continue with Database operations on a separate thread.