User navigates between different screen or app, it goes through different states in their lifecycle. So an activity lifecycle consists of 7 different methods of android.app.Activity class i.e :
onCreate() : In this state, the activity is created.
onStart() : This callback method is called when the activity becomes visible to the user.
onResume() : The activity is in the foreground and the user can interact with it.
onPause() : Activity is partially obscured by another activity. Other activity that’s in the foreground is semi-transparent.
onStop() : The activity is completely hidden and not visible to the user.
onDestroy() : Activity is destroyed and removed from the memory.
