视图是黑色的，当返回到导航控制器堆栈视图时，在实现自定义转换后

Question

我有一个包含元素列表的表格视图。在点击表格视图中的单元格时，我尝试实现到详细视图的缩放转换。 过渡按预期工作 - 但是当我按“返回”时，我被带到一个黑色视图。

我是使用自定义过渡的新手，所以也许我缺少一些东西 - 我只是不确定是什么。我按照这篇文章：https://blog.rocketinsights.com/how-to-create-a-navigation-transition-like-the-apple-news-app/ 进行了缩放转换，并将代码转换为 Swift 4。

这是我的 zoomtransition 类：

class ZoomTransitionAnimator: NSObject, UIViewControllerAnimatedTransitioning {

    private let duration: TimeInterval = 0.5
    var operation: UINavigationControllerOperation = .push
    var thumbnailFrame = CGRect.zero

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

    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        let presenting = operation == .push

        // Determine which is the master view and which is the detail view that we're navigating to and from. The container view will house the views for transition animation.
        let containerView = transitionContext.containerView
        guard let toView = transitionContext.view(forKey: UITransitionContextViewKey.to) else { return }
        guard let fromView = transitionContext.view(forKey: UITransitionContextViewKey.from) else { return }
        let storyFeedView = presenting ? fromView : toView
        let storyDetailView = presenting ? toView : fromView

        // Determine the starting frame of the detail view for the animation. When we're presenting, the detail view will grow out of the thumbnail frame. When we're dismissing, the detail view will shrink back into that same thumbnail frame.
        var initialFrame = presenting ? thumbnailFrame : storyDetailView.frame
        let finalFrame = presenting ? storyDetailView.frame : thumbnailFrame

        // Resize the detail view to fit within the thumbnail's frame at the beginning of the push animation and at the end of the pop animation while maintaining it's inherent aspect ratio.
        let initialFrameAspectRatio = initialFrame.width / initialFrame.height
        let storyDetailAspectRatio = storyDetailView.frame.width / storyDetailView.frame.height
        if initialFrameAspectRatio > storyDetailAspectRatio {
            initialFrame.size = CGSize(width: initialFrame.height * storyDetailAspectRatio, height: initialFrame.height)
        }
        else {
            initialFrame.size = CGSize(width: initialFrame.width, height: initialFrame.width / storyDetailAspectRatio)
        }

        let finalFrameAspectRatio = finalFrame.width / finalFrame.height
        var resizedFinalFrame = finalFrame
        if finalFrameAspectRatio > storyDetailAspectRatio {
            resizedFinalFrame.size = CGSize(width: finalFrame.height * storyDetailAspectRatio, height: finalFrame.height)
        }
        else {
            resizedFinalFrame.size = CGSize(width: finalFrame.width, height: finalFrame.width / storyDetailAspectRatio)
        }

        // Determine how much the detail view needs to grow or shrink.
        let scaleFactor = resizedFinalFrame.width / initialFrame.width
        let growScaleFactor = presenting ? scaleFactor: 1/scaleFactor
        let shrinkScaleFactor = 1/growScaleFactor

        if presenting {
            // Shrink the detail view for the initial frame. The detail view will be scaled to CGAffineTransformIdentity below.
            storyDetailView.transform = CGAffineTransform(scaleX: shrinkScaleFactor, y: shrinkScaleFactor)
            storyDetailView.center = CGPoint(x: thumbnailFrame.midX, y: thumbnailFrame.midY)
            storyDetailView.clipsToBounds = true
        }

        // Set the initial state of the alpha for the master and detail views so that we can fade them in and out during the animation.
        storyDetailView.alpha = presenting ? 0 : 1
        storyFeedView.alpha = presenting ? 1 : 0

        // Add the view that we're transitioning to to the container view that houses the animation.
        containerView.addSubview(toView)
        containerView.bringSubview(toFront: storyDetailView)

        // Animate the transition.
        UIView.animate(withDuration: duration, delay: 0.0, usingSpringWithDamping: 1, initialSpringVelocity: 1.0, options: [.curveEaseInOut], animations: {
            // Fade the master and detail views in and out.
            storyDetailView.alpha = presenting ? 1 : 0
            storyFeedView.alpha = presenting ? 0 : 1

            if presenting {
                // Scale the master view in parallel with the detail view (which will grow to its inherent size). The translation gives the appearance that the anchor point for the zoom is the center of the thumbnail frame.
                let scale = CGAffineTransform(scaleX: growScaleFactor, y: growScaleFactor)
                let translate = storyFeedView.transform.translatedBy(x: storyFeedView.frame.midX - self.thumbnailFrame.midX, y: storyFeedView.frame.midY - self.thumbnailFrame.midY)
                storyFeedView.transform = translate.concatenating(scale)
                storyDetailView.transform = .identity
            }
            else {
                // Return the master view to its inherent size and position and shrink the detail view.
                storyFeedView.transform = .identity
                storyDetailView.transform = CGAffineTransform(scaleX: shrinkScaleFactor, y: shrinkScaleFactor)
            }

            // Move the detail view to the final frame position.
            storyDetailView.center = CGPoint(x: finalFrame.midX, y: finalFrame.midY)
        }) { finished in
            transitionContext.completeTransition(finished)
        }
    }

}

在我的主视图控制器中，我使用以下代码实现了 UINavigationControllerDelegate：

extension SearchVC: UINavigationControllerDelegate {

    func navigationController(_ navigationController: UINavigationController, animationControllerFor operation: UINavigationControllerOperation, from fromVC: UIViewController, to toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        if operation == .push {

            //Pass the thumbnail frame to the transition animator.
            guard let transitionThumbnail = transitionThumbnail, let transitionThumbnailSuperview = transitionThumbnail.superview else { return nil }

            thumbnailZoomTransitionAnimator = ZoomTransitionAnimator()
            thumbnailZoomTransitionAnimator?.thumbnailFrame = transitionThumbnailSuperview.convert(transitionThumbnail.frame, to: nil)
        }
        thumbnailZoomTransitionAnimator?.operation = operation

        return thumbnailZoomTransitionAnimator
    }

}

最后，当点击表格视图中的一个单元格时，这是我的代码：

func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    tableView.deselectRow(at: indexPath as IndexPath, animated: true)

    let cell = tableView.cellForRow(at: indexPath as IndexPath) as? MovieTableViewCell
    transitionThumbnail = cell?.movieImageView

    self.performSegue(withIdentifier: "searchToDetails", sender: indexPath.row)
}

我的 segue 以“prepare for segue”方法将数据发送到详细视图。

谁能解释/帮助我出了什么问题？ :-) 只有在返回时才提到，视图变黑了。

Answer 1

我认为您需要在动画完成后设置呈现才能处理切换。

    { finished in
        transitionContext.completeTransition(finished)
        presenting = !presenting
    }