Firstly, to make UIStackView scrollable, embed it inside UIScrollView. Read How to embed UIStackView inside UIScrollView in iOS
It's best to listen to keyboardWillChangeFrameNotification as it contains frame changes for Keyboard in different situation like custom keyboard, languages.
Posted immediately prior to a change in the keyboard’s frame.
class KeyboardHandler { let scrollView: UIScrollView let stackView: UIStackView var observer: AnyObject? var keyboardHeightConstraint: NSLayoutConstraint! struct Info { let frame: CGRect let duration: Double let animationOptions: UIView.AnimationOptions } init(scrollView: UIScrollView, stackView: UIStackView) { self.scrollView = scrollView self.stackView = stackView } } To make scrollView scroll beyond its contentSize, we can change its contentInset.bottom. Another way is to add a dummy view with certain height to UIStackView and alter its NSLayoutConstraint constant
We can't access self inside init, so it's best to have setup function
func setup() { let space = UIView() keyboardHeightConstraint = space.heightAnchor.constraint(equalToConstant: 0) NSLayoutConstraint.on([keyboardHeightConstraint]) stackView.addArrangedSubview(spa observer = NotificationCenter.default.addObserver( forName: UIResponder.keyboardWillChangeFrameNotification, object: nil, queue: .main, using: { [weak self] notification in self?.handle(notification) } ) } Convert Notification to a convenient Info struct
func convert(notification: Notification) -> Info? { guard let frameValue = notification.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] NSValue, let durationotification.userInfo?[UIResponder.keyboardAnimationDurationUserInfoKey] as? NSNumber, let raw = notification.userInfo?[UIResponder.keyboardAnimationCurveUserInfoKey] NSNumber else { return nil return Info( frame: frameValue.cgRectValue, duration: duration.doubleValue, animationOptions: UIView.AnimationOptions(rawValue: raw.uintValue) ) } Then we can compare with UIScreen to check if Keyboard is showing or hiding
func handle(_ notification: Notification) { guard let info = convert(notification: notification) else { return let isHiding = info.frame.origin.y == UIScreen.main.bounds.height keyboardHeightConstraint.constant = isHiding ? 0 : info.frame.hei UIView.animate( withDuration: info.duration, delay: 0, options: info.animationOptions, animations: { self.scrollView.layoutIfNeeded() self.moveTextFieldIfNeeded(info: info) }, completion: nil) } To move UITextField we can use scrollRectToVisible(_:animated:) but we have little control over how much we want to scroll
This method scrolls the content view so that the area defined by rect is just visible inside the scroll view. If the area is already visible, the method does nothing.
Another way is to check if keyboard overlaps UITextField. To do that we use convertRect:toView: with nil target so it uses window coordinates. Since keyboard frame is always relative to window, we have frames in same coordinate space.
Converts a rectangle from the receiver’s coordinate system to that of another view.
rect: A rectangle specified in the local coordinate system (bounds) of the receiver.
view: The view that is the target of the conversion operation. If view is nil, this method instead converts to window base coordinates. Otherwise, both view and the receiver must belong to the same UIWindow object.
func moveTextFieldIfNeeded(info: Info) { guard let input = stackView.arrangedSubviews .compactMap({ $0 as? UITextField }) .first(where: { $0.isFirstResponder }) else { return let inputFrame = input.convert(input.bounds, to: nil) if inputFrame.intersects(info.frame) { scrollView.setContentOffset(CGPoint(x: 0, y: inputFrame.height), animated: true) } else { scrollView.setContentOffset(.zero, animated: true) } } Original post https://github.com/onmyway133/blog/issues/329
Top comments (0)