title: onResume/onPause on iOS application
body: <p>On Android, when I write an application, I need to implement onResume/onPause for my activity to go to background and come back from foreground. I have googled if I need how to to the same thing for iOS. But I can't find anything useful. Can you please tell me what do I need to do to handle my iOS app going to background and coming back to foreground?</p>
  
  <p>Thank you.</p>