Keyboard & textfields layout - swift3

Question

I'm posting this to hopefully help people have encountered the same problem as I have, and for answers on one question.
In one UIViewController I have multiple textfields, some located above the keyboard and some will be located beneath the keyboard. At the same time I have a toolbar located above the keyboard to toggle through the UITextFields.
This is what the view looks like:
To set the right origin of the textfields I have compiled codes from different answer into this code:
To register for keyboardShow and Hide:
override function viewDidLoad() {
NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillShow), name: .UIKeyboardWillShow, object: nil)
NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillHide), name: .UIKeyboardWillHide, object: nil)
}
KeyboardWillShow selector method:
func keyboardWillShow(_ notification: Notification) {
if let userInfo = notification.userInfo,
let keyboard = (userInfo[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue.size {
let keyboardHeight = self.view.frame.height - keyboard.height
for (_, textField) in textFields.enumerated() {
let textFieldBottom = textField.frame.origin.y + textField.frame.height
let dif = textFieldBottom - keyboardHeight
if textFieldBottom >= keyboardHeight {
if textField.isFirstResponder {
self.view.frame.origin.y = 0
self.view.frame.origin.y -= dif
}
}
}
}
}
KeyboardWillHide selector method:
func keyboardWillHide(_ notification: Notification) {
view.frame.origin.y = 0
}
My question is now, when I quickly tap one of the arrows in my toolbar the code will not move the necessary distance, so that the correct UITextField is just above the keyboard.
Example: First Incorrect Answer is the firstResponder. I tap twice quickly on > arrow. Second Incorrect Answer will be the UITextField just above the keyboard while Third Incorrect Answer will be the firstResponder and not viewable by the user.