动画后呈现视图控制器消失

Question

我有一个 TabBarController，其中显示了一个带有 UIViewControllerAnimatedTransitioning 的自定义动画的视图控制器；

动画正常运行没有问题，但是animationController(forPresented)函数运行后，Presenting view controller消失了。

我在这里发现了一个问题，人们有同样的问题，但这些尝试都没有解决我的问题。

我读到 iOS 中存在一个错误，我们应该再次将“消失”的视图控制器添加到堆栈中，但是将其添加到 UIApplication.shared.keyWindow?.addSubview(presentingView) 会使视图添加到 presentedView 之上，而我没有'不知道它再次添加它，将另一个添加到堆栈中，因为它可能只是一个图形错误并且视图仍然是容器的一部分。

这里有一些代码：

// Global var
var transition = Animator()

// Present a VC modally using tab bar
func tabBarController(_ tabBarController: UITabBarController, shouldSelect viewController: UIViewController) -> Bool {
    if viewController is NewPostVC {
        if let newVC = tabBarController.storyboard?.instantiateViewController(withIdentifier: "newPostVC") as? NewPostVC {
            newVC.transitioningDelegate = self
            newVC.interactor = interactor // new
            tabBarController.present(newVC, animated: true)
            return false
        }
    }
    return true
}

// Handles the presenting animation
func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
    transition.transitioningMode = .Present
    return transition
}


// Handles the dismissing animation
func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
    transition.transitioningMode = .Dismiss
    return transition
}


// interaction controller, only for dismissing the view;
func interactionControllerForDismissal(using animator: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning? {
    return interactor.hasStarted ? interactor : nil
}


//*****************************
/// On the Animator class:
func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        let containerView = transitionContext.containerView

        // Animates to present
        if transitioningMode == .Present {

            // Get views
            guard
                let presentedView = transitionContext.view(forKey: UITransitionContextViewKey.to),
                let presentingView = transitionContext.view(forKey: UITransitionContextViewKey.from)
                else {
                    print("returning")
                    return
            }

            // Add the presenting view controller to the container view
            containerView.addSubview(presentingView)

            // Add the presented view controller to the container view
            containerView.addSubview(presentedView)

            // Animate
            UIView.animate(withDuration: presentDuration, animations: { 

                presentingView.transform = CGAffineTransform.identity.scaledBy(x: 0.85, y: 0.85);
                presentingView.layer.cornerRadius = 7.0
                presentingView.layer.masksToBounds = true

                presentedView.transform = CGAffineTransform.identity.scaledBy(x: 0.6, y: 0.6);
                presentedView.layer.masksToBounds = true

            }, completion: { _ in
                // On completion, complete the transition
                transitionContext.completeTransition(true)

                //UIApplication.shared.keyWindow?.addSubview(presentingView) 
            })


        }
        // Animates to dismiss
        else {
            // TODO: - Implement reverse animation
        }
    }

请注意，动画本身只是我正在做的测试，只是缩放它们。

谢谢。

Answer 1

看了苹果的相关文档here后发现presentingViewController从屏幕上消失不是bug，而是API的工作原理。

任何使用传输动画的人都可以阅读文档，该文档已更新，您会在其中找到非常有趣和扎实的解释。