void RegisterNotifications()
{
if (_eventListeners == null) {
_eventListeners = new List<NSObject> ();
}
_eventListeners.Add (NSNotificationCenter.DefaultCenter.AddObserver (UIApplication.DidChangeStatusBarOrientationNotification,
PositionHUD));
_eventListeners.Add (NSNotificationCenter.DefaultCenter.AddObserver (UIKeyboard.WillHideNotification,
PositionHUD));
_eventListeners.Add (NSNotificationCenter.DefaultCenter.AddObserver (UIKeyboard.DidHideNotification,
PositionHUD));
_eventListeners.Add (NSNotificationCenter.DefaultCenter.AddObserver (UIKeyboard.WillShowNotification,
PositionHUD));
_eventListeners.Add (NSNotificationCenter.DefaultCenter.AddObserver (UIKeyboard.DidShowNotification,
PositionHUD));
}