ios - 自定义推送过渡不起作用，而相同的自定义呈现过渡有效

Question

我关注了this tutorial并观看了the WWDC video关于这个主题，但我找不到答案。

我的代码中有几乎相同的转换。当我将其作为呈现 View 而不是推送 View 时，它工作得很好。

它应该将推送 View 的快照从 CGRect 动画化到全屏，反之亦然。

这是我的 UIViewControllerAnimatedTransitioning 类的代码:

class ZoomingTransitionController: NSObject, UIViewControllerAnimatedTransitioning {

    let originFrame: CGRect
    let isDismissing: Bool

    init(originFrame: CGRect, isDismissing: Bool) {
        self.originFrame = originFrame
        self.isDismissing = isDismissing
    }

    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return Constant.Animation.VeryShort
    }

    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        let containerView = transitionContext.containerView

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

        let finalFrame = transitionContext.finalFrame(for: toVC)

        toVC.view.frame = finalFrame

        let snapshot = self.isDismissing ? fromVC.view.snapshotView(afterScreenUpdates: true) : toVC.view.snapshotView(afterScreenUpdates: true)
        snapshot?.frame = self.isDismissing ? finalFrame : self.originFrame
        snapshot?.layer.cornerRadius = Constant.FakeButton.CornerRadius
        snapshot?.layer.masksToBounds = true

        containerView.addSubview(toVC.view)
        containerView.addSubview(snapshot!)

        if self.isDismissing {
            fromVC.view.isHidden = true
        } else {
            toVC.view.isHidden = true
        }

        let duration = transitionDuration(using: transitionContext)

        UIView.animate(withDuration: duration,
                       animations: {
            snapshot?.frame = self.isDismissing ? self.originFrame : finalFrame
            },
                       completion: { _ in
                        if self.isDismissing {
                            fromVC.view.isHidden = false
                        } else {
                            toVC.view.isHidden = false
                        }

                        snapshot?.removeFromSuperview()
                        transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
        })
    }
}

然后，我尝试使用两种方式展示一个新的 View Controller :呈现它和推送它。

我的 FromViewController 是 UINavigationControllerDelegate 和 UIViewControllerTransitioningDelegate 的子类。

FromViewController 类 呈现 ToViewController(工作正常):

func buttonAction(_ sender: AnyObject) {
    self.tappedButtonFrame = sender.frame

    let toVC = self.storyboard!.instantiateViewController(withIdentifier: "ToViewController")
    toVC.transitioningDelegate = self

    self.present(toVC, animated: true, completion: nil)
}

func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
    let transitionController = ZoomingTransitionController(originFrame: self.tappedButtonFrame, isDismissing: false)

    return transitionController
}

func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
    let transitionController = ZoomingTransitionController(originFrame: self.tappedButtonFrame, isDismissing: true)

    return transitionController
}

FromViewController 类推送 ToViewController(不起作用):

func buttonAction(_ sender: AnyObject) {
    self.tappedButtonFrame = sender.frame

    let toVC = self.storyboard!.instantiateViewController(withIdentifier: "ToViewController")

    self.navigationController?.pushViewController(toVC, animated: true)
}

func navigationController(_ navigationController: UINavigationController, animationControllerFor operation: UINavigationControllerOperation, from fromVC: UIViewController, to toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {
    switch operation {
    case .push:
        return ZoomingTransitionController(originFrame: self.tappedButtonFrame, isDismissing: false)

    case .pop:
        return ZoomingTransitionController(originFrame: self.tappedButtonFrame, isDismissing: true)

    default:
        return nil
    }
}

当推送 时，委托(delegate)方法被调用并且 ZoomingTransitionController 正常执行其代码(进入 animateTransition 直到结束没有明显问题)。但是在屏幕上，任何时候都不会显示快照 View 。 ToVC 出现在过渡持续时间之后，但同时没有任何其他内容。

我完全不知道如何调试它...你有什么想法吗？

谢谢!!

Answer 1

我通过将快照元素(导致问题的原因)替换为 toVC 的 CGAffineTransform 找到了答案。

代码与here 几乎相同.