KeyboardDidShow called when keyboard isn't shown - swift

Question

so I've set up keyboard observers using KeyboardDidShow so that I can shift the view up only when the keyboard is shown. However, KeyboardDidShow runs at the launch of every view and also at random times. I've tried monitoring the keyboard frames and only shifting the view if the frame changes, but every so often the view is still shifted even without the keyboard being shown. Usually, it happens whenever the view is first launched, so I tried adding a delay but it's not very dependable.
DispatchQueue.main.asyncAfter(deadline: .now() + 1.0) {
NotificationCenter.default.addObserver(self, selector: #selector(self.keyboardDidShow(_:)), name: NSNotification.Name.UIKeyboardDidShow, object: nil)
}
#objc func keyboardDidShow(_ notification: Notification) {
let userInfo = notification.userInfo!
let beginFrameValue = (userInfo[UIKeyboardFrameBeginUserInfoKey] as? NSValue)!
let beginFrame = beginFrameValue.cgRectValue
let endFrameValue = (userInfo[UIKeyboardFrameEndUserInfoKey] as? NSValue)!
let endFrame = endFrameValue.cgRectValue
if beginFrame.equalTo(endFrame) {
return
} else {
let indexPath = IndexPath(item: 0, section: 0)
if UIScreen.main.bounds.height == 812 {
collectionView?.contentInset = UIEdgeInsets(top: 318 + view.safeAreaInsets.bottom, left: 0, bottom: 73, right: 0)
}
collectionView?.scrollToItem(at: indexPath, at: .bottom, animated: true)
}
}

Answer 1

The problem is that you have configured the wrong notification. Do not use UIKeyboardDidShow. Use UIKeyboardWillShow, and examine the old frame, the new frame, and whether the new frame will cover your view.
Arriving at a robust implementation is not trivial, but it is certainly a well established previously solved problem that has been explained here many times.

Answer 2

For UIViewController instances you need observer these notifications only when view is visible and not subscribe to notification multiple times. Best way to do so is:
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
NotificationCenter.default.addObserver(self, selector: #selector(onKeyboardWillChangeFrame(_:)), name: UIResponder.keyboardWillChangeFrameNotification, object: nil)
}
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
NotificationCenter.default.removeObserver(self, name: UIResponder.keyboardWillChangeFrameNotification, object: nil)
}
And here is working code from my project to handle keayboard frame
#objc private func onKeyboardWillChangeFrame(_ notification: NSNotification) {
// extract values
if let userInfo = notification.userInfo,
let keyboardFrameEnd = (userInfo[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue,
let animationCurveInt = (userInfo[UIResponder.keyboardAnimationCurveUserInfoKey] as? NSNumber)?.intValue {
/*
СУКАБЛЯТЬ
With upgrate to Swift 4.2 UIView.AnimationCurve(rawValue: 7) returns actual instance of
UIView.AnimationCurve which crashes on access, mod by 4 limits value to max
*/
let animationCurve = UIView.AnimationCurve(rawValue: animationCurveInt % 4) ?? .easeIn
// View chanages
let topPoint = self.view.convert(keyboardFrameEnd.origin, from: self.view.window)
let height = self.view.bounds.size.height - topPoint.y
... update your constraints or manually update vars that affect layoutSubviews()...
let animationDuration: TimeInterval = (userInfo[UIResponder.keyboardAnimationDurationUserInfoKey] as? NSNumber)?.doubleValue ?? 0
var animationOptions: UIView.AnimationOptions = []
switch animationCurve {
case .easeInOut: animationOptions = .curveEaseInOut
case .easeIn: animationOptions = .curveEaseIn
case .easeOut: animationOptions = .curveEaseOut
case .linear: animationOptions = .curveLinear
}
// run animation
UIView.animate(withDuration: animationDuration, delay: 0, options: animationOptions, animations: {
self.view.layoutIfNeeded()
})
}
}