Question

I detect when the keyboard will show with the below code. However, when I push to another screen using pushViewController and open the keyboard in that screen, keyboardWillShow is getting called! Is this really correct?

[[NSNotificationCenter defaultCenter] addObserver:self 
                                         selector:@selector(keyboardWillShow:) 
                                             name:UIKeyboardWillShowNotification 
                                           object:nil];
// register for keyboard notifications
[[NSNotificationCenter defaultCenter] addObserver:self 
                                         selector:@selector(keyboardWillHide:) 
                                             name:UIKeyboardWillHideNotification 
                                           object:nil];

Answer 1

Yes, this is correct behavior.
Since the view that pushes the other view is still alive and the notifications are app wide.

You could remove the notification in the:

- (void)viewDidDisappear:(BOOL)animated {
    [super viewDidDisappear:animated];

    [[NSNotificationCenter defaultCenter] removeObserver:self 
                                                    name:UIKeyboardWillShowNotification 
                                                  object:nil];

    [[NSNotificationCenter defaultCenter] removeObserver:self 
                                                    name:UIKeyboardWillHideNotification 
                                                  object:nil];
}

And if you want to set the observer then place you code from viewDidLoad to viewWillAppear:(BOOL)animated:

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    [[NSNotificationCenter defaultCenter] addObserver:self 
                                         selector:@selector(keyboardWillShow:) 
                                             name:UIKeyboardWillShowNotification 
                                           object:nil];
    // register for keyboard notifications
    [[NSNotificationCenter defaultCenter] addObserver:self 
                                         selector:@selector(keyboardWillHide:) 
                                             name:UIKeyboardWillHideNotification 
                                           object:nil];
}