Snapshot view is hidden while performing UIViewControllerAnimatedTransitioning - ios

Question

I am trying to make a simple animated transitioning when pushing a UIViewController, but it seems I am missing something.
I animate a snapshot of a subview from the fromViewController to the toViewController. I am animating snapshot’s frame, but the snapshot is invisible for the whole duration of the animation.
Here is a simple code example. I am trying to animate a single UILabel from the first controller to the second. I specifically want to animate a snapshot taken from the toViewConroller and not from the fromViewController.
func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
let fromVC = transitionContext.viewController(forKey: .from) as! ViewController
let toVC = transitionContext.viewController(forKey: .to) as! SecondViewController
let container = transitionContext.containerView
toVC.view.frame = fromVC.view.frame
container.addSubview(toVC.view)
toVC.view.layoutIfNeeded()
let animatedFromView = fromVC.label!
let animatedToView = toVC.label!
let initialFrame = container.convert(animatedFromView.frame,
from: animatedFromView.superview)
let finalFame = container.convert(animatedToView.frame,
to: animatedToView.superview)
let snapshot = animatedToView.snapshotView(afterScreenUpdates: true)!
snapshot.frame = initialFrame
container.addSubview(snapshot)
animatedFromView.alpha = 0
animatedToView.alpha = 0
UIView.animate(withDuration: 2,
animations: {
snapshot.frame = finalFame
}) { (_) in
snapshot.removeFromSuperview()
fromVC.label.alpha = 1
toVC.label.alpha = 1
transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
}
}
I guess that the snapshot is hidden, because setting the animatedToView’s alpha to 0, however I am not sure how to achieve that animation without setting that.

Answer 1

I tried your code its working fine.I changed a few things like initial frame hardcoded it so i can see the effect and also from viewController alpha.
::::::for presenting view controller
func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
let fromVC = transitionContext.viewController(forKey: .from) as! ViewController
let toVC = transitionContext.viewController(forKey: .to) as! SecondViewController
let container = transitionContext.containerView
toVC.view.frame = fromVC.view.frame
container.addSubview(toVC.view)
toVC.view.layoutIfNeeded()
let animatedFromView = fromVC.view!
let animatedToView = toVC.view!
let initialFrame = container.convert(CGRect(x: 0, y: 200, width: 100, height: 100),
from: animatedFromView.superview)
let finalFame = container.convert(animatedToView.frame,
to: animatedToView.superview)
let snapshot = animatedToView.snapshotView(afterScreenUpdates: true)!
snapshot.frame = initialFrame
container.addSubview(snapshot)
animatedFromView.alpha = 1
animatedToView.alpha = 0
UIView.animate(withDuration: 2,
animations: {
snapshot.frame = finalFame
}) { (_) in
snapshot.removeFromSuperview()
fromVC.view.alpha = 1
toVC.view.alpha = 1
transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
}
}
:::::::::::::::::
Use while you are pushing view controller
func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
guard let fromView = transitionContext.view(forKey: UITransitionContextViewKey.from) else { return }
guard let toView = transitionContext.view(forKey: UITransitionContextViewKey.to) else { return }
let container = transitionContext.containerView
container.insertSubview(toView, belowSubview: fromView)
let animatedFromView = fromView
let animatedToView = toView
let initialFrame = container.convert(CGRect(x: 0, y: 200, width: 100, height: 100),
from: animatedFromView.superview)
let finalFame = container.convert(animatedToView.frame,
to: animatedToView.superview)
let snapshot = animatedToView.snapshotView(afterScreenUpdates: true)!
snapshot.frame = initialFrame
container.addSubview(snapshot)
animatedFromView.alpha = 1
animatedToView.alpha = 1
UIView.animate(withDuration: 2,
animations: {
snapshot.frame = finalFame
}) { (_) in
snapshot.removeFromSuperview()
//fromVC.view.alpha = 1
//toVC.view.alpha = 1
transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
}
}