UIKeyboardWillShowNotification called twice if screen rotates - ios

Question

I create notifications when the keyboard appears and disappears.
override func viewDidLoad() {
super.viewDidLoad()
// Creates notification when keyboard appears and disappears
NSNotificationCenter.defaultCenter().addObserver(self, selector: Selector("keyboardWillShow:"), name: UIKeyboardWillShowNotification, object: nil)
NSNotificationCenter.defaultCenter().addObserver(self, selector: Selector("keyboardWillHide:"), name: UIKeyboardWillHideNotification, object: nil)
}
override func viewWillDisappear(animated: Bool) {
NSNotificationCenter.defaultCenter().removeObserver(self, name: UIKeyboardWillShowNotification, object: nil)
NSNotificationCenter.defaultCenter().removeObserver(self, name: UIKeyboardWillHideNotification, object: nil)
}
func keyboardWillShow(notification: NSNotification) {
self.adjustingHeight(true, notification: notification)
}
func keyboardWillHide(notification: NSNotification) {
self.adjustingHeight(false, notification: notification)
}
private func adjustingHeight(show: Bool, notification: NSNotification) {
// Gets notification information in an dictionary
var userInfo = notification.userInfo!
// From information dictionary gets keyboard’s size
let keyboardFrame:CGRect = (userInfo[UIKeyboardFrameBeginUserInfoKey] as! NSValue).CGRectValue()
// Gets the time required for keyboard pop up animation
let animationDurarion = userInfo[UIKeyboardAnimationDurationUserInfoKey] as! NSTimeInterval
// Animation moving constraint at same speed of moving keyboard & change bottom constraint accordingly.
if !(show && self.bottomConstraint.constant != self.bottomConstraintConstantDefault) {
if show {
self.bottomConstraint.constant = (CGRectGetHeight(keyboardFrame) + self.bottomConstraintConstantDefault / 2)
} else {
self.bottomConstraint.constant = self.bottomConstraintConstantDefault
}
UIView.animateWithDuration(animationDurarion) {
self.view.layoutIfNeeded()
}
}
self.hideLogoIfSmall()
}
The strange behaviour occurs when the keyboard is already shown and I rotate the screen. Then the next actions occurs:
UIKeyboardWillHideNotification called
UIKeyboardWillShowNotification called (with the old height of the keyboard)
UIKeyboardWillShowNotification called (with the new height of the keyboard)
The result of this is that my view is not updated properly because the first time UIKeyboardWillShowNotification is called I receive a different height of the keyboard than the second time.

Answer 1

Finally I found the solution. When I get keyboardFrame, I was using UIKeyboardFrameBeginUserInfoKey which returns the frame of the keyboard before the animation begins. The correct way of do that is with UIKeyboardFrameEndUserInfoKeywhich returns the frame of the keyboard after the animation has completed.
let keyboardFrame: CGRect = (userInfo[UIKeyboardFrameEndUserInfoKey] as! NSValue).CGRectValue()
Now UIKeyboardWillShowNotification is called twice but returns the same height of the keyboard in both calls.