Crash when using UIView.animateKeyframes - NSInternalInconsistencyException: You must provide a value (key=contents)

Something is trying to create an animation for the CALayer.contents, and in this case since contents is likely nil on whatever view is being animated its tripping over an assumption in the keyframe animation tracking that the value provided will not be nil. Since only specific views will animate contents it's unusual that a tracking data structure is even being created for that key.

We would certainly appreciate a feedback request with all the information you have on hand.

Thanks for your reply, the error message definitely makes sense now.

What you will find below :

• The code of the ViewController where the crash is occurring (I have omitted styling and data related code)
• The code of the CustomSearchBar and a preview of its view hierarchy from the Interface Builder
• The complete stack trace (Incident.crash)

Some explanation regarding the controller properties :

• extendedNavBarContainerView: vertical UIStackView used to expand the navigationBar, it contains the searchContainerView.
• searchContainerView: horizontal UIStackView containing the searchBar and the cancelButton.

The extendedNavBarContainerView is placed below the navigationBar with the help of the additionalSafeAreaInsets property while being constrained to the top of the safe area. In my code, it also contains another view in addition to the searchContainerView (Could the crash be caused from this additional view ? I don't think so since I'm calling layoutIfNeeded() on the cancelButton superview, which is searchContainerView). Initially, the extendedNavBarContainerView is hidden, and is animated in with the method showExtendedNavBar() when the data has loaded, allowing the user to search through. Next, the cancelButton is animated in when the searchBarTextField becomes the first responder and begins editing, and is animated out on tap.

Let me know if I missed something and you would like further information.

class ViewController: UICollectionViewController {

  // MARK: - Properties
  lazy var searchBar = CustomSearchBar.loadFromNib()
  lazy var cancelButton = UIButton(type: .system)
  lazy var searchContainerView = UIStackView()
  lazy var extendedNavBarContainerView = UIStackView()

  // MARK: - Lifecycle
  override func viewDidLoad() {
		super.viewDidLoad()
		setupSearchBar()
		setupNavigationBar()
	}

	// MARK: - Setup
	private func setupSearchBar() {
		searchBar.searchTextField.delegate = self

		cancelButton.alpha = 0
		cancelButton.isHidden = true
		cancelButton.setContentHuggingPriority(.required, for: .horizontal)

		searchContainerView.axis = .horizontal
		searchContainerView.alignment = .center
		searchContainerView.distribution = .fill
		searchContainerView.insetsLayoutMarginsFromSafeArea = false
		searchContainerView.isLayoutMarginsRelativeArrangement = true

		searchContainerView.addArrangedSubview(searchBar)
		searchContainerView.addArrangedSubview(cancelButton)
  }

	private func setupNavigationBar() {
		extendedNavBarContainerView.isHidden = true
		extendedNavBarContainerView.axis = .vertical
		extendedNavBarContainerView.alignment = .fill
		extendedNavBarContainerView.distribution = .fill
		extendedNavBarContainerView.insetsLayoutMarginsFromSafeArea = false
		extendedNavBarContainerView.isLayoutMarginsRelativeArrangement = true
		extendedNavBarContainerView.translatesAutoresizingMaskIntoConstraints = false

		extendedNavBarContainerView.addArrangedSubview(searchContainerView)
		view.addSubview(extendedNavBarContainerView)

		NSLayoutConstraint.activate([
			extendedNavBarContainerView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
			extendedNavBarContainerView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
			extendedNavBarContainerView.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor)
		])
	}

	// MARK: - Actions
	func showExtendedNavBar() {
		let itemsHeight = [searchContainerHeight]
		let extendedNavBarHeight = extendedNavBarHeight(with: itemsHeight)
		extendedNavBarContainerView.isHidden = false

		UIView.animate(withDuration: Layout.animationDuration) {
			self.additionalSafeAreaInsets.top = extendedNavBarHeight
			self.view.layoutIfNeeded()
		}
	}

	func hideExtendedNavBar() {
			UIView.animate(withDuration: Layout.animationDuration) {
				self.additionalSafeAreaInsets.top = 0
				self.view.layoutIfNeeded()
			} completion: { _ in
				self.extendedNavBarContainerView.isHidden = true
			}
	}

	// MARK: - Search
	func showSearchBarCancelButton() {
		let duration = Layout.animationDuration
		let options = Layout.cancelButtonAnimationOptions

		UIView.animateKeyframes(withDuration: duration, delay: 0, options: options, animations: {
			UIView.addKeyframe(withRelativeStartTime: 0.0, relativeDuration: 1, animations: {
				self.cancelButton.isHidden = false
				self.cancelButton.superview?.layoutIfNeeded()
			})
			UIView.addKeyframe(withRelativeStartTime: 0.7, relativeDuration: 0.3, animations: {
				self.cancelButton.alpha = 1
			})
		})
	}

	func hideSearchBarCancelButton() {
		let duration = Layout.animationDuration
		let options = Layout.cancelButtonAnimationOptions

		UIView.animateKeyframes(withDuration: duration, delay: 0, options: options, animations: {
			UIView.addKeyframe(withRelativeStartTime: 0.0, relativeDuration: 1, animations: {
				self.cancelButton.isHidden = true
				self.cancelButton.superview?.layoutIfNeeded()
			})
			UIView.addKeyframe(withRelativeStartTime: 0.0, relativeDuration: 0.3, animations: {
				self.cancelButton.alpha = 0
			})
		})
	}

	// MARK: - Delegate
	func textFieldDidBeginEditing(_ textField: UITextField) {
		showSearchBarCancelButton()
	}

	func textFieldShouldReturn(_ textField: UITextField) -> Bool {
		textField.resignFirstResponder()
		return false
	}
}

CustomSearchBar

class CustomSearchBar: UIView {

  // MARK: - IBOutlets
  @IBOutlet weak var backgroundView: UIView!
  @IBOutlet weak var searchTextField: UITextField!

  // MARK: - Properties
  override var intrinsicContentSize: CGSize {
    let inset = UIEdgeInsets(insets: [layoutMargins, backgroundView.layoutMargins])
    let height = inset.vertical + searchTextField.intrinsicContentSize.height
    return .init(width: UIView.noIntrinsicMetric, height: height)
  }

  // MARK: - Lifecycle
  override func awakeFromNib() {
    super.awakeFromNib()
    setupView()
  }

  // MARK: - Setup
  private func setupView() {
    backgroundView.layer.cornerRadius = 10
  }

  // MARK: - Actions
  @IBAction func onSearchBarTap(_ sender: Any) {
    searchTextField.becomeFirstResponder()
  }
}

Thanks again for your help!

There seems to be a fair amount of missing setup and some missing extensions – I cut back what I could to get this to compile but couldn't reproduce the issue. Given what is happening in your keyframe animation, my immediate suspicion would be something about UIButton, but I don't have a ton of context to provide there.

It would help to file a feedback request with a complete project (post the FB number here and I can track it earlier) just so that we can both be sure we are looking at the same thing.

Thanks!

My bad, didn't think you wanted to run the code.
I could throw an app update while changing the button type from system to custom and see if it helps.

I have filed a feedback request at https://bugreport.apple.com, the number is FB13593988
I have also uploaded a project on Github at https://github.com/Reqven/iOS-Crash-UIView.animateKeyframes

Let me know if there is anything else I can do.
Thanks!