Callback for "Activity not started, its current task has been brought to the front"?

I understand that if my app is already running and I haven't made any code changes, LogCat displays the following warning:

ActivityManager: Warning: Activity not started, its cur开发者_StackOverflow社区rent task has been brought to the front

What I don't understand is why no activity lifecycle like onResume() or onRestart() is called.

The app was not visible before I tried to re-run it, so why no onResume() or onRestart() callback was called?

Are you sure onResume() is not called? In all of my code I see onResume being called. Perhaps a sample code post showing the contrary.