TextFieldVisibility.swift

class SomeClass: UIViewController
{
    var firstResponder: UIView? /// To handle textField position when keyboard is visible.
    var isKeyboardVisible = false /// You can handle tap on view by checking if keyboard is visible.
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        /*
         Register notifications for when keyboard appears/disappears
         Note that we don't remove the observers if target iOS is iOS 9.0 or later
         Apples Doc:
         If your app targets iOS 9.0 and later or macOS 10.11 and later, you don't need to unregister an observer in its dealloc method.
         */
        NotificationCenter.default.addObserver(self, selector: #selector(keyboardNotification(_:)), name: UIResponder.keyboardWillShowNotification, object: nil)
        NotificationCenter.default.addObserver(self, selector: #selector(keyboardNotification(_:)), name: UIResponder.keyboardWillHideNotification, object: nil)
    }
    
    @objc
    fileprivate func keyboardNotification(_ notification: Notification) {
        
        self.isKeyboardVisible.toggle()
        
        if notification.name == UIResponder.keyboardWillShowNotification {
            guard let keyboardValue = notification.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue else { return }
            
            let keyboardFrame = keyboardValue.cgRectValue
            
            // Note that textView delegate gets called later that keyboard notification unlike TextFields.
            // So if firstResponder variable is nil it means our textView is firstRespnder.
            if let textField = self.firstResponder ?? self.textView {
                let textFieldPoints = textField.convert(textField.frame.origin, to: self.view.window)
                let textFieldRect   = textField.convert(textField.frame, to: self.view.window)
                
                let contentInset = UIEdgeInsets(top: 0, left: 0, bottom: keyboardFrame.height + textField.frame.height, right: 0)
                
                self.scrollView.contentInset = contentInset
                self.scrollView.scrollIndicatorInsets = contentInset
                
                // visible part of the view, where is not covered by the keyboard.
                var windowFrame = self.view.frame
                windowFrame.size.height -= keyboardFrame.height
                
                // if you don't see the firstResponder view in visible part, means the view is beneth the keyboard.
                if !windowFrame.contains(textFieldPoints) {
                    self.scrollView.scrollRectToVisible(textFieldRect, animated: true)
                }
            }
        }
        
        if notification.name == UIResponder.keyboardWillHideNotification {
            self.scrollView.contentInset = .zero
            self.scrollView.scrollIndicatorInsets = .zero
        }
    }
}

// MARK: Delegates

extension SomeClass: UITextFieldDelegate
{
    
    // MARK: TextField Delegate
    
    func textFieldDidBeginEditing(_ textField: UITextField) {
        self.firstResponder = textField // We set the firstResponder variable to active textField,
        // This then will be handled in keyboardNotification()
    }
    
    func textFieldDidEndEditing(_ textField: UITextField) {
        self.firstResponder = nil
    }
    
    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        textField.resignFirstResponder()
        return true
    }
    
}