I am getting following warning when I try to present a ActivityController on navigation controller,
Attempt to present
You are trying to present a view controller from the rootViewController. In your case I think the rootViewController is not the current ViewController. Either you presented or pushed a new UIViewController on top of it. You should present a view controller from the top most view controller itself.
You need to change:
UIViewController *vc = self.view.window.rootViewController;
[vc presentViewController: activityController animated: YES completion:nil];
to:
[self presentViewController: activityController animated: YES completion:nil];