UIKeyboardWillHideNotification called in rotation

Question

I had implemented this:

[[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(keyboardWillShow:) name:UIKeyboardWillShowNotification object:nil];
[[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(keyboardWillHide:) name:UIKeyboardWillHideNotification object:nil];

Because I have an scroller and other things. But the problem is that the iPad has a button in the keyboard to hide the keyboard, but it doesn't stop editing (the flashing line remains)

I want that if he hides the keyboards, the text resign itself after the time of keyboard animation. This works fine.

BUT If I rotate, the method is called and the textField resigns itself (Is called not even once, but three times)

How do I stop UIKeyboardWillHideNotification to fire when the UI rotates?

If that is not the way, how do I properly resign responder when that button is tapped?

Here is my code:

float keyboardHeightSize;
- (void)keyboardWillShow:(NSNotification*)notification {
    keyboardHeightSize = [[[notification userInfo]objectForKey:UIKeyboardFrameEndUserInfoKey]CGRectValue].size.height;

    [_scroller setContentSize:CGSizeMake(0, 1954+keyboardHeightSize)];

}

- (void)keyboardWillHide:(NSNotification*)notification {

    [_scroller setContentSize:(CGSizeMake(0, 1954))];

    CGFloat keyboardAnimationDuration = [[[notification userInfo]objectForKey:UIKeyboardAnimationDurationUserInfoKey] floatValue];

    [self performSelector:@selector(resignResponders) withObject:nil afterDelay:keyboardAnimationDuration];

}

-(void)resignResponders {

    for (id textField in self.scroller.subviews)
    {
        if ([textField isKindOfClass:[UITextField class]])
        {
            UITextField *theTextField = textField;
            if ([theTextField isFirstResponder]) {
                [theTextField resignFirstResponder];

            }

        }
    }

}