我有一个演示应用程序，我正在尝试模仿邮件应用程序“新消息”交互式转换 - 您可以向下拖动以关闭，但如果您没有拖动足够远，视图会弹回并取消转换。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对象内的演示和关闭代码：
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)
}
}
解除过渡
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，我使用这个 Ray Wenderlich 教程作为参考 - https://www.raywenderlich.com/322-custom-uiviewcontroller-transitions-getting-started 但是他们使用图像快照来为过渡设置动画我正在使用视图控制器的意见。