UIViewController 交互式过渡 - 取消交互式关闭时呈现的视图消失

Posted 2023-03-10

【中文标题】UIViewController 交互式过渡 - 取消交互式关闭时呈现的视图消失

【英文标题】：UIViewController interactive transition - Presented view disappears when interactive dismiss is canceled

【发布时间】：2019-01-09 18:58:03

【问题描述】：

我有一个演示应用程序，我试图在其中模仿邮件应用程序“新消息”交互式转换 - 您可以向下拖动以关闭，但如果您没有拖得足够远，视图会弹回并且转换是取消。我能够在我的演示应用程序中复制过渡和交互性，但是我注意到当取消过渡被取消时，呈现的视图控制器被动画回原位，然后消失。这是它的样子：

我最好的猜测是转换上下文的容器视图由于某种原因被删除了，因为我向其中添加了呈现的视图控制器的视图。这是UIViewControllerAnimatedTransitioning 对象中的演示和关闭代码：

显示过渡

func animateTransition(using transitionContext: UIViewControllerContextTransitioning) 
    guard let fromVC = transitionContext.viewController(forKey: .from),
        let toVC = transitionContext.viewController(forKey: .to)
        else 
            return
    

    let containerView = transitionContext.containerView
    let finalFrame = transitionContext.finalFrame(for: toVC)
    let duration = transitionDuration(using: transitionContext)
    let topSafeAreaSpace = fromVC.view.safeAreaInsets.top // using fromVC safe area since it's on screen and has correct insets
    let topGap: CGFloat = topSafeAreaSpace + 20

    containerView.addSubview(toVC.view)

    toVC.view.frame = CGRect(x: 0,
                             y: containerView.frame.height,
                             width: toVC.view.frame.width,
                             height: toVC.view.frame.height - 30)

    UIView.animate(withDuration: duration, animations: 
        toVC.view.frame = CGRect(x: finalFrame.minX,
                                 y: finalFrame.minY + topGap,
                                 width: finalFrame.width,
                                 height: finalFrame.height - topGap)

        let sideGap: CGFloat = 20
        fromVC.view.frame = CGRect(x: sideGap,
                                   y: topSafeAreaSpace,
                                   width: fromVC.view.frame.width - 2 * sideGap,
                                   height: fromVC.view.frame.height - 2 * topSafeAreaSpace)
        fromVC.view.layer.cornerRadius = 10
        fromVC.view.layoutIfNeeded()
    )  _ in
        transitionContext.completeTransition(true)
    

关闭过渡

func animateTransition(using transitionContext: UIViewControllerContextTransitioning) 
    guard let fromVC = transitionContext.viewController(forKey: .from),
        let toVC = transitionContext.viewController(forKey: .to)
        else 
            return
    

    let finalFrame = transitionContext.finalFrame(for: toVC)
    let duration = transitionDuration(using: transitionContext)

    UIView.animate(withDuration: duration, animations: 
        toVC.view.frame = finalFrame
        fromVC.view.frame = CGRect(x: fromVC.view.frame.minX,
                                   y: finalFrame.height,
                                   width: fromVC.view.frame.width,
                                   height: fromVC.view.frame.height)

        toVC.view.layer.cornerRadius = 0

        toVC.view.layoutIfNeeded()
    )  _ in
        transitionContext.completeTransition(true)
    

这是UIPercentDrivenInteractiveTransition对象中的代码：

func handleGesture(_ gesture: UIPanGestureRecognizer) 
    #warning("need to use superview?")
    let translation = gesture.translation(in: gesture.view)
    var progress = translation.y / 400
    progress = min(1, max(0, progress)) // constraining value between 1 and 0

    switch gesture.state 
    case .began:
        interactionInProgress = true
        viewController.dismiss(animated: true, completion: nil)
    case .changed:
        shouldCompleteTransition = progress > 0.5
        update(progress)
    case .cancelled:
        interactionInProgress = false
        cancel()
    case .ended:
        interactionInProgress = false
        if shouldCompleteTransition 
            finish()
         else 
            cancel()
        
    default:
        break
    

任何帮助将不胜感激。值得注意的是，我使用了这个 Ray Wenderlich 教程作为参考 - https://www.raywenderlich.com/322-custom-uiviewcontroller-transitions-getting-started 然而，在他们使用图像快照为过渡设置动画的地方，我使用了视图控制器的视图。

【问题讨论】：

您是否尝试过将 false 传递给 transitionContext.completeTransition(_:)？根据文档，“如果到呈现的视图控制器的转换成功完成，则为 true，如果仍在显示原始视图控制器，则为 false。” developer.apple.com/documentation/uikit/…

哇，我的疏忽了。谢谢@Dare！

【参考方案1】：

感谢@Dare 的评论，我意识到所需要的只是对关闭动画完成块的小更新：

// before - broken

transitionContext.completeTransition(true)

// after - WORKING!

transitionContext.completeTransition(!transitionContext.transitionWasCancelled)