Don't agree with that : the activity manage one or more fragment so we need to listen to the fragment state.
I tried with isRemoving() or isDetached() but none is true at this point.
The better could be to implement the onDestroy() maybe.
I'm not at all good at Android stuff, but I'm sure here we have a bug to fix. For example when the Fragment is detached from the activity, the fragment onPause() calls the ApplicationListener to pause(), then the fragment onDestroy() but the ApplicationListener never dispose()... so when the fragment onCreate() is called again, the ApplicationListener create() is done without the dispose() before... and this can cause some bad things !