自定义 UIViewControllerAnimatedTransitioning 完成后显示黑屏

Question

我有一个 segue，它是通过一个按钮触发的，该按钮在当前上下文中以模态方式显示另一个视图控制器。我正在使用自定义类来自定义过渡，这是这样的：

class ShowAnimator: NSObject {
}


extension ShowAnimator: UIViewControllerAnimatedTransitioning {
func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
    return 0.5
}
func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
    guard
        let fromVC = transitionContext.viewController(forKey: .from),
        let toVC = transitionContext.viewController(forKey: .to) else {
            return
    }
    let containerView = transitionContext.containerView
    containerView.insertSubview(fromVC.view, belowSubview: toVC.view)
    let toFrame = transitionContext.finalFrame(for: toVC)
    let screenBounds = UIScreen.main.bounds
    let bottomLeftCorner = CGPoint(x: screenBounds.width, y: 0)
    let finalFrame = CGRect(origin: bottomLeftCorner, size: screenBounds.size)

    UIView.animate(withDuration: transitionDuration(using: transitionContext),
                   animations: {
                    fromVC.view.frame = finalFrame
    },
                   completion: { _ in
                    transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
    }
    )
}
}

在我的主视图控制器中，我有以下相关功能：

let showAnimator = ShowAnimator()
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    let destination = segue.destination
    destination.transitioningDelegate = self
}


func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
    return nil
}
func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
    return showAnimator
}

请注意，这个类是一个 ViewController 以及一个UIViewControllerTransitioningDelegate 但是，每当我按下按钮来执行我的转场时，它都会正确地执行动画，但是一旦完成，它只会显示一个黑屏，而不是下一个 ViewController。

Answer 1

一个问题是这一行：

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

您正在插入fromVC视图。那是错的。它已经存在（尽管不一定在容器中）。

而且您没有插入toVC视图。那也是错误的。您需要将其放入容器中。