Nsryjdtyk

i´m trying to make my own interactive transition in swift. In my sample project I have two view controllers. With my own transition I can swipe to each other. My problem is: when swiping from the first to the second view controller the second (where I want to swipe in) view controller is appears for a millisecond on the screen, when I did cancel the transition in my pan gesture.

I tried to solve the problem by taking a snapshot from the first view controller and lay it on the transition layer when the transition cancelled. That worked on my iPhone 8, but on the iPhone XS I get the same flash for a millisecond.

The flashing only appears when I swipe very fast over the screen.

Anyone with the same problem.

PangestureHandler:

@IBAction func HandlePan(_ sender: UIPanGestureRecognizer) {

    let percentThreshold:CGFloat = 0.25



    let translation = sender.translation(in: view)

    var verticalMovement = (translation.y) / view.bounds.height

    verticalMovement = verticalMovement - verticalMovement - verticalMovement

    let downwardMovement = fmaxf(Float(verticalMovement), 0.0)

    let downwardMovementPercent = fminf(downwardMovement, 1.0)

    let progress = CGFloat(downwardMovementPercent)



    let movementToStart: CGFloat = 0.0



    let interactor = self.interactor



    switch sender.state {

    case .began:

        print(".began")

    case .changed:

        print("progress: (progress)")

        if progress > movementToStart && !interactor.hasStarted {

            interactor.hasStarted = true

            performSegue(withIdentifier: "segueToSecondVC", sender: nil)

            interactor.update(progress - movementToStart)

        }

        if interactor.hasStarted {

            interactor.update(progress - movementToStart)

            interactor.shouldFinish = progress > percentThreshold

        }

    case .cancelled:

        print("cancel")

        interactor.hasStarted = false

        interactor.cancel()

    case .ended:

        interactor.hasStarted = false

        if interactor.shouldFinish {

            interactor.finish()

        } else {

            interactor.cancel()

            print("interactor cancel")

        }



    default:

        break

    }

}

AnimatorClass:

import UIKit



class PresentAnimator: NSObject, UIViewControllerAnimatedTransitioning {









private var myView: UIView!



func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {

    return 0.6



}





func animationEnded(_ transitionCompleted: Bool) {

    if !transitionCompleted {

        self.myView.alpha = 1.0

    }

}



func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {

    guard let fromVC = transitionContext.viewController(forKey: .from), let toVC = transitionContext.viewController(forKey: .to) else { return }

    let containerView = transitionContext.containerView





    let screenBounds = UIScreen.main.bounds

    let startPoint = CGPoint(x: 0, y: UIScreen.main.bounds.height )

    toVC.view.frame = CGRect(origin: startPoint, size: screenBounds.size)

    toVC.view.clipsToBounds = true



    self.myView = fromVC.view.snapshotView(afterScreenUpdates: false)

    containerView.addSubview(myView)

    self.myView.alpha = 0.0



    containerView.insertSubview(toVC.view, aboveSubview: fromVC.view)



    let bottomLeftCorner = CGPoint(x: 0, y: 0)

    let finalFrame = CGRect(origin: bottomLeftCorner, size: screenBounds.size)

    let duration = transitionDuration(using: transitionContext)







    UIView.animate(

        withDuration: duration, delay: 10.0, options: .curveLinear,

        animations: {

            toVC.view.frame = finalFrame

            self.myView.removeFromSuperview()

    },

        completion: { _ in

            self.myView.removeFromSuperview()

            transitionContext.completeTransition(!transitionContext.transitionWasCancelled)

    })



}

}