UIViewControllerAnimatedTransitioning doesn't complete on iOS 9/10, but works iOS 11 and later? - swift

Question

I have a custom presentation controller which shows a UIViewController as a "bottom sheet" above the current ViewController, and allows an interactive gesture to dismiss the presented modal. The modal's modalPresentationStyle is set to .current, and the transitioningDelegate is set to my custom class during init(). The current code works perfectly on iOS 11 and 12, but appears to "freeze" the device on iOS 9 and 10.
Here is where the animation takes place. I have confirmed the presentedFrame and dismissedFrame are correct.
extension BottomSheetPresentationManager: UIViewControllerAnimatedTransitioning {
func transitionDuration(
using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
return 0.25
}
func interactionControllerForPresentation(using animator: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning? {
return self
}
func interactionControllerForDismissal(using animator: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning? {
return self
}
func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
let key = presenting ? UITransitionContextViewControllerKey.to
: UITransitionContextViewControllerKey.from
let keyV = presenting ? UITransitionContextViewKey.to
: UITransitionContextViewKey.from
let controller = transitionContext.viewController(forKey: key)!
let view = transitionContext.view(forKey: keyV)!
if presenting {
transitionContext.containerView.addSubview(view)
}
let presentedFrame = transitionContext.finalFrame(for: controller)
var dismissedFrame = presentedFrame
switch direction {
case .left:
dismissedFrame.origin.x = -presentedFrame.width
case .right:
dismissedFrame.origin.x = transitionContext.containerView.frame.size.width
case .top:
dismissedFrame.origin.y = -presentedFrame.height
case .bottom:
dismissedFrame.origin.y = transitionContext.containerView.frame.size.height
}
let initialFrame = presenting ? dismissedFrame : presentedFrame
let finalFrame = presenting ? presentedFrame : dismissedFrame
// Runs when the animation finishes
let completionBlock: (Bool) -> Void = { (finished) in
// tell our transitionContext object that we've finished animating
if transitionContext.transitionWasCancelled {
if self.interactive {
transitionContext.cancelInteractiveTransition()
}
transitionContext.completeTransition(false)
} else {
if self.interactive {
finished ? transitionContext.finishInteractiveTransition() : transitionContext.cancelInteractiveTransition()
}
transitionContext.completeTransition(finished)
}
}
// Put what you want to animate here.
let animationBlock: () -> Void = {
view.frame = finalFrame
}
// Set up for the animation
let animationDuration = transitionDuration(using: transitionContext)
view.frame = initialFrame
// Perform a different animation based on whether we're interactive (performing a gesture) or not
if interactive {
// Do a linear animation so we match our dragging with our transition
UIView.animate(withDuration: animationDuration,
delay: 0,
options: .curveLinear,
animations: animationBlock,
completion: completionBlock)
} else {
// Do a spring animation with easing
UIView.animate(withDuration: animationDuration,
delay: 0,
usingSpringWithDamping: 0.8,
initialSpringVelocity: 0.45,
options: [.curveEaseInOut],
animations: animationBlock,
completion: completionBlock)
}
}
}
After much testing, I have figured out that the completion block on the UIView.animate block never gets called (completionBlock in the code), and in the Capture View Hierarchy view, it actually shows my presented view on top, with what looks like a screenshot of the view (UIVisualEffectView) directly under the presented menu.
What you are seeing there is my bottom menu (the UITableView with cells that you see in front), with a UIVisualEffectView behind it (appears to be a screenshot of the UICollection view behind that), and a UICollectionView that called the present() method for the menu.
What would cause the UIView.animate block not to complete? Is there any reason the behavior would differ between iOS 10 and 11? Any help would be greatly appreciated.