iOS Swift: Custom interactive transition - ios

Question

I wrote a custom swipe transition that works fine on a modal presentation. But in a push presentation the "to" view position is not animating.
I've tried the same code with switching the translation with alpha and it works.
The from view works perfectly, it's just the to view that stays fixed during the animation.
func transitionAnimator(using transitionContext: UIViewControllerContextTransitioning) -> UIViewImplicitlyAnimating {
let duration = transitionDuration(using: transitionContext)
let container = transitionContext.containerView
let toController = transitionContext.viewController(forKey: .to)
toController?.beginAppearanceTransition(true, animated: true)
guard
let to = transitionContext.view(forKey: .to),
let from = transitionContext.view(forKey: .from)
else {
print("To or from view are nil!")
fatalError()
}
container.addSubview(to)
let animator = UIViewPropertyAnimator(duration: duration, curve: .linear)
var toStartingPoint: CGPoint
var fromEndingPoint: CGPoint
switch self.from {
case .down:
toStartingPoint = CGPoint(x: 0, y: -from.bounds.height)
fromEndingPoint = CGPoint(x: 0, y: from.bounds.height)
case .top:
toStartingPoint = CGPoint(x: 0, y: from.bounds.height)
fromEndingPoint = CGPoint(x: 0, y: -from.bounds.height)
case .right:
toStartingPoint = CGPoint(x: from.bounds.width, y: 0)
fromEndingPoint = CGPoint(x: -from.bounds.width, y: 0)
case .left:
toStartingPoint = CGPoint(x: -from.bounds.width, y: 0)
fromEndingPoint = CGPoint(x: from.bounds.width, y: 0)
}
to.transform = CGAffineTransform(translationX: toStartingPoint.x, y: toStartingPoint.y)
animator.addAnimations({
from.transform = CGAffineTransform(translationX: fromEndingPoint.x, y: fromEndingPoint.y)
}, delayFactor: 0.0)
animator.addAnimations({
to.transform = .identity
}, delayFactor: 0.0)
animator.addCompletion { [weak self] position in
switch position {
case .start:
self?.auxCancelCompletion?()
transitionContext.completeTransition(false)
self?.auxAnimationsCancel?()
case .end:
self?.auxEndCompletion?()
transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
from.transform = .identity
to.transform = .identity
default:
transitionContext.completeTransition(false)
self?.auxAnimationsCancel?()
}
}
if let auxAnimations = auxAnimations {
animator.addAnimations(auxAnimations)
}
self.animator = animator
self.context = transitionContext
animator.addCompletion { [unowned self] _ in
self.animator = nil
self.context = nil
}
animator.isUserInteractionEnabled = true
return animator
}
I was thinking that was a problem about delegates but the navigationDelgate is correctly set, otherwise I think I wouldn't see any animation..
Delegate setting:
override func viewDidLoad() {
super.viewDidLoad()
transitionHelper = SwipeInteractiveTransitionHelper(withDelegate: self)
}
extension TodayViewController: UINavigationControllerDelegate {
func navigationController(_ navigationController: UINavigationController, animationControllerFor operation: UINavigationController.Operation, from fromVC: UIViewController, to toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {
return transitionHelper?.swipeTransition
}
func navigationController(_ navigationController: UINavigationController, interactionControllerFor animationController: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning? {
return transitionHelper?.swipeTransition
}
}
and here is the custom push coordinator, where the viewController is the next view controller, and where I attach the delegate.
case .pushCustom:
guard let navigationController = currentViewController.navigationController else {
fatalError("Can't push a view controller without a current navigation controller")
}
guard let current = currentViewController as? UINavigationControllerDelegate else {
fatalError("Can't push a view controller without a current navigation delegate")
}
navigationController.delegate = current
navigationController.pushViewController(viewController, animated: true) { [weak self] in
self?.currentViewController = SceneCoordinator.actualViewController(for: viewController)
completion?()
}

Answer 1

Solved animating a snapshot of the destination view, instead of directly animating the destination view.
let to = transitionContext.view(forKey: .to)
let toViewSnapshot = to.snapshotView(afterScreenUpdates: true)
Just use the toViewSnapshot for the animation

Answer 2

What I did is this way. Hope it will help you.
VC:UIViewController
{
#IBAction func test(_ sender: Any){
navigationController?.delegate = self
let destine = storyboard?.instantiateViewController(withIdentifier: "target")
navigationController?.pushViewController(destine!, animated: true)
}
func navigationController(_ navigationController: UINavigationController, animationControllerFor operation: UINavigationController.Operation, from fromVC: UIViewController, to toVC: UIViewController) -> UIViewControllerAnimatedTransitioning?{
return Traistion()
}
}
class Traistion: NSObject, UIViewControllerAnimatedTransitioning{
func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
let animator = transitionAnimator(using: transitionContext)
animator.startAnimation()
}
var animator: UIViewPropertyAnimator!
var context: UIViewControllerContextTransitioning!
func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval{
return 1.0
}
enum Direction {
case down
case top
case left
case right
}
var from : Direction = .left
var auxCancelCompletion :(()->())? = {
return nil
}()
var auxAnimationsCancel :(()->())? = {
return nil
}()
var auxEndCompletion :(()->())? = {
return nil
}()
var auxAnimations : (()->())?
func transitionAnimator(using transitionContext: UIViewControllerContextTransitioning) -> UIViewImplicitlyAnimating {
let duration = transitionDuration(using: transitionContext)
let container = transitionContext.containerView
let toController = transitionContext.viewController(forKey: .to)
toController?.beginAppearanceTransition(true, animated: true)
guard
let to = transitionContext.view(forKey: .to),
let from = transitionContext.view(forKey: .from)
else {
print("To or from view are nil!")
fatalError()
}
container.addSubview(to)
let animator = UIViewPropertyAnimator(duration: duration, curve: .linear)
var toStartingPoint: CGPoint
var fromEndingPoint: CGPoint
switch self.from {
case .down:
toStartingPoint = CGPoint(x: 0, y: -from.bounds.height)
fromEndingPoint = CGPoint(x: 0, y: from.bounds.height)
case .top:
toStartingPoint = CGPoint(x: 0, y: from.bounds.height)
fromEndingPoint = CGPoint(x: 0, y: -from.bounds.height)
case .right:
toStartingPoint = CGPoint(x: from.bounds.width, y: 0)
fromEndingPoint = CGPoint(x: -from.bounds.width, y: 0)
case .left:
toStartingPoint = CGPoint(x: -from.bounds.width, y: 0)
fromEndingPoint = CGPoint(x: from.bounds.width, y: 0)
}
to.transform = CGAffineTransform(translationX: toStartingPoint.x, y: toStartingPoint.y)
animator.addAnimations({
from.transform = CGAffineTransform(translationX: fromEndingPoint.x, y: fromEndingPoint.y)
}, delayFactor: 0.0)
animator.addAnimations({
to.transform = .identity
}, delayFactor: 0.0)
animator.addCompletion { [weak self] position in
switch position {
case .start:
self?.auxCancelCompletion?()
transitionContext.completeTransition(false)
self?.auxAnimationsCancel?()
case .end:
self?.auxEndCompletion?()
transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
from.transform = .identity
to.transform = .identity
default:
transitionContext.completeTransition(false)
self?.auxAnimationsCancel?()
}
}
if let auxAnimations = auxAnimations {
animator.addAnimations(auxAnimations)
}
self.animator = animator
self.context = transitionContext
animator.addCompletion { [unowned self] _ in
//self.animator = nil
// self.context = nil
}
animator.isUserInteractionEnabled = true
return animator
}
}
When use interruptibleAnimator. It will call this function at least twice and you are supposed to provide the same animator but different one. So you have to call it like this way:
func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
animator = transitionAnimator(using: transitionContext) as! UIViewPropertyAnimator
animator.startAnimation()
}
func interruptibleAnimator(using transitionContext: UIViewControllerContextTransitioning) -> UIViewImplicitlyAnimating {
return animator
}
var animator: UIViewPropertyAnimator!
var context: UIViewControllerContextTransitioning!
or simpler like this:
func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
}
func interruptibleAnimator(using transitionContext: UIViewControllerContextTransitioning) -> UIViewImplicitlyAnimating {
if animator == nil {animator = transitionAnimator(using: transitionContext) as! UIViewPropertyAnimator
animator.startAnimation()}
return animator
}
Here animator will be called twice and which is the same one. If
func interruptibleAnimator(using transitionContext: UIViewControllerContextTransitioning) -> UIViewImplicitlyAnimating {
return transitionAnimator(using: transitionContext) }
This is not the right way to use as the animator will be different.
https://developer.apple.com/documentation/uikit/uiviewcontrolleranimatedtransitioning/1829434-interruptibleanimator
See the last line in the document.