AutoLayout_keyboard.swift

@objc private func keyboardWillShow(notification: Notification) {
  if let userInfo = notification.userInfo, let keyboardSize = (userInfo[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue {
    if passwordTextField.frame.maxY > (view.frame.height - keyboardSize.height) {
      imageViewTopConstraint.constant = -1 * (passwordTextField.frame.maxY - (view.frame.height - keyboardSize.height))
    }
  }
}

@objc private func keyboardWillHide(notification: Notification) {
  imageViewTopConstraint.constant = 0
}

AutoLayout_nicer_keyboard_with_animation.swift

@objc private func keyboardWillShow(notification: Notification) {
  if let userInfo = notification.userInfo,
    let keyboardSize = (userInfo[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue,
    let duration = (userInfo[UIResponder.keyboardAnimationDurationUserInfoKey] as? NSNumber)?.doubleValue {
    if passwordTextField.frame.maxY > (view.frame.height - keyboardSize.height) {
      UIView.animate(withDuration: duration, animations: {
        self.imageViewTopConstraint.constant = -1 * (self.passwordTextField.frame.maxY - (self.view.frame.height - keyboardSize.height))
        self.view.layoutIfNeeded()
      })
    }
  }
}

@objc private func keyboardWillHide(notification: Notification) {
  if let userInfo = notification.userInfo,
    let duration = (userInfo[UIResponder.keyboardAnimationDurationUserInfoKey] as? NSNumber)?.doubleValue {
    UIView.animate(withDuration: duration) {
      self.imageViewTopConstraint.constant = 0
      self.view.layoutIfNeeded()
    }
  }
}

AutoLayout_notification_center.swift

override func viewWillAppear(_ animated: Bool) {
  super.viewWillAppear(animated)
  NotificationCenter.default.addObserver(self, selector: #selector(LoginViewController.keyboardWillShow), name: UIResponder.keyboardWillShowNotification, object: nil)
  NotificationCenter.default.addObserver(self, selector: #selector(LoginViewController.keyboardWillHide), name: UIResponder.keyboardWillHideNotification, object: nil)
}

override func viewWillDisappear(_ animated: Bool) {
  super.viewWillDisappear(animated)
  NotificationCenter.default.removeObserver(self)
}