Using UIPercentDrivenInteractiveTransition with CABasicAnimation has weird glitch - swift

Question

I'm implementing custom transition using CABasicAnimation and UIView.animate both. Also need to implement a custom interactive transition using UIPercentDrivenInteractiveTransition which exactly copies the behavior of the native iOS swipe back. Animation without a back swipe gesture (when I'm pushing and popping by the back arrow) works fine and smoothly. Moreover, swipe back also works smoothly, except when the gesture velocity is more than 900
Gesture Recognition function:
#objc func handleBackGesture(_ gesture: UIScreenEdgePanGestureRecognizer) {
guard animationTransition != nil else { return }
switch gesture.state {
case .began:
interactionController = TransparentNavigationControllerTransitionInteractor(duration: anumationDuration)
popViewController(animated: true)
case .changed:
guard let view = gesture.view?.superview else { return }
let translation = gesture.translation(in: view)
var percentage = translation.x / view.bounds.size.width
percentage = min(1.0, max(0.0, percentage))
shouldCompleteTransition = percentage > 0.5
interactionController?.update(percentage)
case .cancelled, .failed, .possible:
if let interactionController = self.interactionController {
isInteractiveStarted = false
interactionController.cancel()
}
case .ended:
interactionController?.completionSpeed = 0.999
let greaterThanMaxVelocity = gesture.velocity(in: view).x > 800
let canFinish = shouldCompleteTransition || greaterThanMaxVelocity
canFinish ? interactionController?.finish() : interactionController?.cancel()
interactionController = nil
#unknown default: assertionFailure()
}
}
UIPercentDrivenInteractiveTransition class. Here I'm synchronizing layer animation.
final class TransparentNavigationControllerTransitionInteractor: UIPercentDrivenInteractiveTransition {
// MARK: - Private Properties
private var context: UIViewControllerContextTransitioning?
private var pausedTime: CFTimeInterval = 0
private let animationDuration: TimeInterval
// MARK: - Initialization
init(duration: TimeInterval) {
self.animationDuration = duration * 0.4 // I dk why but layer duration should be less
super.init()
}
// MARK: - Public Methods
override func startInteractiveTransition(_ transitionContext: UIViewControllerContextTransitioning) {
super.startInteractiveTransition(transitionContext)
context = transitionContext
pausedTime = transitionContext.containerView.layer.convertTime(CACurrentMediaTime(), from: nil)
transitionContext.containerView.layer.speed = 0
transitionContext.containerView.layer.timeOffset = pausedTime
}
override func finish() {
restart(isFinishing: true)
super.finish()
}
override func cancel() {
restart(isFinishing: false)
super.cancel()
}
override func update(_ percentComplete: CGFloat) {
super.update(percentComplete)
guard let transitionContext = context else { return }
let progress = CGFloat(animationDuration) * percentComplete
transitionContext.containerView.layer.timeOffset = pausedTime + Double(progress)
}
// MARK: - Private Methods
private func restart(isFinishing: Bool) {
guard let transitionLayer = context?.containerView.layer else { return }
transitionLayer.beginTime = transitionLayer.convertTime(CACurrentMediaTime(), from: nil)
transitionLayer.speed = isFinishing ? 1 : -1
}
}
And here is my Dismissal animation function in UIViewControllerAnimatedTransitioning class
private func runDismissAnimationFrom(
_ fromView: UIView,
to toView: UIView,
in transitionContext: UIViewControllerContextTransitioning) {
guard let toViewController = transitionContext.viewController(forKey: .to) else { return }
toView.frame = toView.frame.offsetBy(dx: -fromView.frame.width / 3, dy: 0)
let toViewFinalFrame = transitionContext.finalFrame(for: toViewController)
let fromViewFinalFrame = fromView.frame.offsetBy(dx: fromView.frame.width, dy: 0)
// Create mask to hide bottom view with sliding
let slidingMask = CAShapeLayer()
let initialMaskPath = UIBezierPath(rect: CGRect(
x: fromView.frame.width / 3,
y: 0,
width: 0,
height: toView.frame.height)
)
let finalMaskPath = UIBezierPath(rect: toViewFinalFrame)
slidingMask.path = initialMaskPath.cgPath
toView.layer.mask = slidingMask
toView.alpha = 0
let slidingAnimation = CABasicAnimation(keyPath: "path")
slidingAnimation.fromValue = initialMaskPath.cgPath
slidingAnimation.toValue = finalMaskPath.cgPath
slidingAnimation.timingFunction = .init(name: .linear)
slidingMask.path = finalMaskPath.cgPath
slidingMask.add(slidingAnimation, forKey: slidingAnimation.keyPath)
UIView.animate(
withDuration: duration,
delay: 0,
options: animationOptions,
animations: {
fromView.frame = fromViewFinalFrame
toView.frame = toViewFinalFrame
toView.alpha = 1
},
completion: { _ in
toView.layer.mask = nil
transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
})
}
I note that glitch occurs only when a swipe has a grand velocity.
Here a video with the result of smooth animation at normal speed and not smooth at high speed - https://youtu.be/1d-kTPlhNvE
UPD:
I've already tried to use UIViewPropertyAnimator combine with
interruptibleAnimator(using transitionContext: UIViewControllerContextTransitioning) -> UIViewImplicitlyAnimating
But the result is another type of glitching.

Answer 1

I've solved the issue, just change a part of restart function:
transitionLayer.beginTime =
transitionLayer.convertTime(CACurrentMediaTime(), from: nil) - transitionLayer.timeOffset
transitionLayer.speed = 1
I don't really understand why, but looks like timeOffset subtraction works!