CGAffineTransform.identity doesn't reset transform correctly after device rotation

Question

I am doing a custom transition and if after present animation, device will be rotated and then destinationVC will be dismissed, originVC transform is not correct (not fulfil screen). If there is no device rotation, everything works perfectly fine. Does any one can help me?

Here is my code for present and dismiss animation:

func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        guard let originViewController = transitionContext.viewController(forKey: .from),
            let destinationViewController = transitionContext.viewController(forKey: .to) else { return }

        destinationViewController.view.transform = CGAffineTransform(translationX: 0, y: destinationViewController.view.frame.height)
        let duration = transitionDuration(using: transitionContext)

        UIView.animate(withDuration: duration, animations: {
            destinationViewController.view.transform = CGAffineTransform(translationX: 0, y: 0)
            originViewController.view.transform = originViewController.view.transform.scaledBy(x: 0.95, y: 0.95)
            originViewController.view.layer.cornerRadius = 8.0
        }, completion: { completed in            
            transitionContext.completeTransition(completed)
        })
    }

func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        guard let originViewController = transitionContext.viewController(forKey: .from),
            let destinationViewController = transitionContext.viewController(forKey: .to) else { return }

        let duration = transitionDuration(using: transitionContext)

        UIView.animate(withDuration: duration, animations: {
            originViewController.view.transform = CGAffineTransform(translationX: 0, y: destinationViewController.view.frame.height)
            destinationViewController.view.transform = CGAffineTransform.identity
            destinationViewController.view.layer.cornerRadius = 0.0
        }, completion: { completed in
            transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
        })
    }

Screens: Before present animation After present animation After device rotation After dismiss animation

EDIT: when I add destinationViewController.view.frame = transitionContext.finalFrame(for: destinationViewController) to dismiss animation everything seems works fine but I don't know if this is right way

Answer 1

Add a subView in ViewC1 with leading, top, bottom, trailing constraints. Working full code

class ViewC1: UIViewController {

    @IBAction func presentNow(_ sender: Any) {
        let viewc = storyboard!.instantiateViewController(withIdentifier: "ViewC2") as! ViewC2
        viewc.transitioningDelegate = viewc
        viewc.modalPresentationStyle = .overCurrentContext
        present(viewc, animated: true, completion: nil)
    }

}

class ViewC2: UIViewController {

    let pres = PresentAnimator()
    let diss = DismissAnimator()

    @IBAction func dissmisNow(_ sender: Any) {
        dismiss(animated: true, completion: nil)
    }
}

extension ViewC2: UIViewControllerTransitioningDelegate {
    func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return pres
    }

    func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return diss
    }
}

class PresentAnimator: NSObject, UIViewControllerAnimatedTransitioning {

    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return 1.0
    }

    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        guard let originViewController = transitionContext.viewController(forKey: .from),
            let destinationViewController = transitionContext.viewController(forKey: .to) else { return }

        transitionContext.containerView.addSubview(destinationViewController.view)
        destinationViewController.view.frame = transitionContext.containerView.bounds

        let originView = originViewController.view.subviews.first

        destinationViewController.view.transform = CGAffineTransform(translationX: 0, y: destinationViewController.view.frame.height)
        let duration = transitionDuration(using: transitionContext)

        UIView.animate(withDuration: duration, animations: {
            destinationViewController.view.transform = CGAffineTransform(translationX: 0, y: 0)
            originView?.transform = CGAffineTransform(scaleX: 0.95, y: 0.95)
            originView?.layer.cornerRadius = 8.0
        }, completion: { completed in
            transitionContext.completeTransition(completed)
        })
    }
}

class DismissAnimator: NSObject, UIViewControllerAnimatedTransitioning {

    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return 1.0
    }

    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        guard let originViewController = transitionContext.viewController(forKey: .from),
            let destinationViewController = transitionContext.viewController(forKey: .to) else { return }

        let originView = destinationViewController.view.subviews.first
        let duration = transitionDuration(using: transitionContext)

        UIView.animate(withDuration: duration, animations: {
            originViewController.view.transform = CGAffineTransform(translationX: 0, y: destinationViewController.view.frame.height)
            originView?.transform = CGAffineTransform.identity
            originView?.layer.cornerRadius = 0.0
        }, completion: { completed in
            transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
        })
    }
}

Update: or you can override willRotate and didRotate if you dont want to use view.subviews.first

var prevTrans: CGAffineTransform?
override func willRotate(to toInterfaceOrientation: UIInterfaceOrientation, duration: TimeInterval) {
    prevTrans = view.transform
    view.transform = CGAffineTransform.identity
}

override func didRotate(from fromInterfaceOrientation: UIInterfaceOrientation) {
    if let prevTrans = prevTrans {
        view.transform = prevTrans
    }
}