LifeCycle Of Activity
onCreate()
onStart()
onResume()
onPause()
onStop()
onDestroy()
MainActivity navigates to SecondActivity
MainActivity onPause()
SecondActivity onCreate()
SecondActivity onStart()
SecondActivity onResume()
MainActivity onStop()
When back button presses (return to MainActivity)
SecondActivity onPause()
MainActivity onRestart()
MainActivity onStart()
MainActivity onResume()
SecondActivity onStop()
SecondActivity onDestroy()