keyboardnotificationcenter.swift

override func viewDidLoad() {
    super.viewDidLoad()
    
    let tap = UITapGestureRecognizer(target: self, action: #selector(dismissKeyboard))
    tap.cancelsTouchesInView = false
    view.addGestureRecognizer(tap)
        
    NotificationCenter.default.addObserver(self, selector: #selector(self.keyboardWillShow(_:)), name: NSNotification.Name.UIKeyboardWillShow, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(self.keyboardWillHide(_:)), name: NSNotification.Name.UIKeyboardWillHide, object: nil)
}