KeyboardHandlingWithTextfields.swift

class ViewController: UIViewController {

    @IBOutlet weak var emailTF: UnderlinedTextField!
    @IBOutlet weak var passwordTF: UnderlinedTextField!
    @IBOutlet weak var backgroundSV: UIScrollView!
    
    static func storyboardInstance() -> Solution3VC? {
        let storyboard = UIStoryboard(name: Storyboard.main ,bundle: nil)
        return storyboard.instantiateViewController(withIdentifier: "Solution3VC") as? Solution3VC
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        //Subscribe to a Notification which will fire before the keyboard will show
        subscribeToNotification(UIResponder.keyboardWillShowNotification, selector: #selector(keyboardWillShowOrHide))
        
        //Subscribe to a Notification which will fire before the keyboard will hide
        subscribeToNotification(UIResponder.keyboardWillHideNotification, selector: #selector(keyboardWillShowOrHide))
        
        //We make a call to our keyboard handling function as soon as the view is loaded.
        initializeHideKeyboard()
    }
    
    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        //Unsubscribe from all our notifications
        unsubscribeFromAllNotifications()
    }

}

extension ViewController {
    
    func initializeHideKeyboard(){
        //Declare a Tap Gesture Recognizer which will trigger our dismissMyKeyboard() function
        let tap: UITapGestureRecognizer = UITapGestureRecognizer(
            target: self,
            action: #selector(dismissMyKeyboard))
        
        //Add this tap gesture recognizer to the parent view
        view.addGestureRecognizer(tap)
    }
    
    @objc func dismissMyKeyboard(){
        //endEditing causes the view (or one of its embedded text fields) to resign the first responder status.
        //In short- Dismiss the active keyboard.
        view.endEditing(true)
    }
}

extension ViewController {
    
    func subscribeToNotification(_ notification: NSNotification.Name, selector: Selector) {
        NotificationCenter.default.addObserver(self, selector: selector, name: notification, object: nil)
    }
    
    func unsubscribeFromAllNotifications() {
        NotificationCenter.default.removeObserver(self)
    }
    
    @objc func keyboardWillShowOrHide(notification: NSNotification) {
        // Get required info out of the notification
        if let scrollView = backgroundSV, let userInfo = notification.userInfo, let endValue = userInfo[UIResponder.keyboardFrameEndUserInfoKey], let durationValue = userInfo[UIResponder.keyboardAnimationDurationUserInfoKey], let curveValue = userInfo[UIResponder.keyboardAnimationCurveUserInfoKey] {
            
            // Transform the keyboard's frame into our view's coordinate system
            let endRect = view.convert((endValue as AnyObject).cgRectValue, from: view.window)
            
            // Find out how much the keyboard overlaps our scroll view
            let keyboardOverlap = scrollView.frame.maxY - endRect.origin.y
            
            // Set the scroll view's content inset & scroll indicator to avoid the keyboard
            scrollView.contentInset.bottom = keyboardOverlap
            scrollView.scrollIndicatorInsets.bottom = keyboardOverlap
            
            let duration = (durationValue as AnyObject).doubleValue
            let options = UIView.AnimationOptions(rawValue: UInt((curveValue as AnyObject).integerValue << 16))
            UIView.animate(withDuration: duration!, delay: 0, options: options, animations: {
                self.view.layoutIfNeeded()
            }, completion: nil)
        }
    }

}