How to detect "Touch to return to call" taps

I have a VoIP-call app, and when the user answers call, sends app to the background and then taps "Touch to return to call" green bar on the top – I want to take additional steps after he returns to the app (show him the in-app call screen instead of the screen presented before the user sends app to the background).

Is there any way to detect/handle these events? Like app delegate's application(continue userActivity:)?

I can't use applicationWillEnterForeground because this event occurred not only when the user taps "Touch to return to call" but even if he just taps the app's icon or returns to the app using the application manager.
How to detect "Touch to return to call" taps
 
 
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