Question

I’m using a background task to complete a few operations when the user suspends my app.
This works fine, but I just noticed that if the user reactivates the app before the background task is finished the screen stays black and applicationWillEnterForeground: is never called.

Once the background task is done all is fine again and applicationWillEnterForeground is called, but is there a way to make the app reactivate while the task is running?

All I could find is to have the background task constantly check the remaining time and notice that this becomes very high when the app is reactivated. It can then end itself and the app appears, but this still means the app is black for half a second or so.

Answer 1

Quick question. Are you using beginBackgroundTaskWithExpirationHandler?

And are you running the actual work asynchronously? As shown in this answer?
objective c – Proper use of beginBackgroundTaskWithExpirationHandler

If not, you should run your long running work on a-sychornously because else it will be executed as part of your main RunLoop. Which will indeed block your apps redraws and responsiveness until the long running task is completed.