iOS 13 风格的 UIPresentationController 不依赖快照？

Question

iOS 13 似乎使用了一个新的 UIPresentationController 来呈现模态视图 Controller ，但它不依赖于拍摄呈现 View Controller 的快照(正如大多数/所有库所做的那样)。当模态视图 Controller 显示在透明/有色背景上方时，呈现 View Controller 是“实时的”并继续显示动画/更改。

我可以通过在呈现 View Controller 的 View 上使用 CGAffineTransform 轻松复制它(因为目的是为 iOS 10/11/12 等制作向后兼容的版本)，但是在旋转设备时，呈现的 View 经常开始变形并超出边界，这似乎是因为系统更新了它的 frame，同时应用了一个事件的 transform。

根据文档，frame 在对 View 应用 transform 时未定义。鉴于系统似乎正在修改框架而不是我，我该如何解决这个问题而不会在我更新呈现 View 的边界时得到 hacky 解决方案？我需要此呈现 Controller 保持通用，因为呈现 Controller 可以是任何形状或形式，不一定是全屏 View 。

这是我目前所拥有的 - 它是一个简单的 UIPresentationController 子类，它似乎工作正常，但是旋转设备然后关闭呈现的 View Controller 似乎会改变呈现 View Controller 的边界(变得太宽或缩小，具体取决于您是在横向/纵向模式下呈现模态 Controller )

class SheetPresentationController: UIPresentationController {
  override var frameOfPresentedViewInContainerView: CGRect {
    return CGRect(x: 40, y: containerView!.bounds.height / 2, width: containerView!.bounds.width-80, height: containerView!.bounds.height / 2)
  }

  override func containerViewWillLayoutSubviews() {
    super.containerViewWillLayoutSubviews()

    if let _ = presentingViewController.transitionCoordinator {
      // We're transitioning - don't touch the frame yet as it'll
      // clash with our transform
    } else {
      self.presentedView?.frame = self.frameOfPresentedViewInContainerView
    }
  }

  override func presentationTransitionWillBegin() {
    super.presentationTransitionWillBegin()

    containerView?.backgroundColor = .clear

    if let coordinator = presentingViewController.transitionCoordinator {
      coordinator.animate(alongsideTransition: { [weak self] _ in
        self?.containerView?.backgroundColor = UIColor.black.withAlphaComponent(0.3)

        // Scale the presenting view
        self?.presentingViewController.view.layer.cornerRadius = 16

        self?.presentingViewController.view.transform = CGAffineTransform.init(scaleX: 0.9, y: 0.9)
        }, completion: nil)
    }
  }

  override func dismissalTransitionWillBegin() {
    if let coordinator = presentingViewController.transitionCoordinator {
      coordinator.animate(alongsideTransition: { [weak self] _ in
        self?.containerView?.backgroundColor = .clear

        self?.presentingViewController.view.layer.cornerRadius = 0
        self?.presentingViewController.view.transform = .identity
        }, completion: nil)
    }
  }
}

还有呈现动画 Controller :

import UIKit

final class PresentingAnimationController: NSObject, UIViewControllerAnimatedTransitioning {
  func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {

    guard let presentedViewController = transitionContext.viewController(forKey: .to) else {
      return
    }

    let springTiming = UISpringTimingParameters(dampingRatio: 1.0, initialVelocity: CGVector(dx:1.0, dy: 1.0))
    let animator: UIViewPropertyAnimator = UIViewPropertyAnimator(duration: transitionDuration(using: transitionContext), timingParameters: springTiming)

    let containerView = transitionContext.containerView
    containerView.addSubview(presentedViewController.view)

    let finalFrameForPresentedView = transitionContext.finalFrame(for: presentedViewController)
    presentedViewController.view.frame = finalFrameForPresentedView

    // Move it below the screen so it slides up
    presentedViewController.view.frame.origin.y = containerView.bounds.height

    animator.addAnimations {
      presentedViewController.view.frame = finalFrameForPresentedView      
    }

    animator.addCompletion { (animationPosition) in
      if animationPosition == .end {
        transitionContext.completeTransition(true)
      }
    }

    animator.startAnimation()
  }

  func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
    return 0.6
  }
}

以及解散动画 Controller :

import UIKit

final class DismissingAnimationController: NSObject, UIViewControllerAnimatedTransitioning {

  func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {

    guard let presentedViewController = transitionContext.viewController(forKey: .from) else {
      return
    }

    guard let presentingViewController = transitionContext.viewController(forKey: .to) else {
      return
    }

    let finalFrameForPresentedView = transitionContext.finalFrame(for: presentedViewController)

    let containerView = transitionContext.containerView
    let offscreenFrame = CGRect(x: finalFrameForPresentedView.minX, y: containerView.bounds.height, width: finalFrameForPresentedView.width, height: finalFrameForPresentedView.height)

    let springTiming = UISpringTimingParameters(dampingRatio: 1.0, initialVelocity: CGVector(dx:1.0, dy: 1.0))
    let animator: UIViewPropertyAnimator = UIViewPropertyAnimator(duration: transitionDuration(using: transitionContext), timingParameters: springTiming)

    animator.addAnimations {
      presentedViewController.view.frame = offscreenFrame
    }

    animator.addCompletion { (position) in
      if position == .end {
        // Complete transition        
        transitionContext.completeTransition(true)
      }
    }

    animator.startAnimation()
  }

  func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
    return 0.6
  }
}

Answer 1

好吧，我明白了。 iOS 13 似乎没有使用缩放变换。正如所解释的那样，在您这样做的那一刻，旋转设备将修改呈现 View 的框架，并且由于您已经将 transform 应用于 View ， View 将以意想不到的方式调整大小并且转换将不再有效。

解决方案是改为使用 z 轴透视图，这会给你完全相同的结果，但这样做会在旋转等情况下幸存下来，因为你所做的只是将 View 移回 3D 空间(Z 轴) ，从而有效地缩小它。这是为我完成此操作的转换 (Swift):

  func calculatePerspectiveTransform() -> CATransform3D {
    let eyePosition:Float = 10.0;
    var contentTransform:CATransform3D = CATransform3DIdentity
    contentTransform.m34 = CGFloat(-1/eyePosition)
    contentTransform = CATransform3DTranslate(contentTransform, 0, 0, -2)
    return contentTransform
  }

这是一篇解释其工作原理的文章:https://whackylabs.com/uikit/2014/10/29/add-some-perspective-to-your-uiviews/

在您的 UIPresenterController 中，您还需要执行以下操作才能正确处理这种跨旋转的转换:

  override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
    super.viewWillTransition(to: size, with: coordinator)

    // Reset transform before we rotate and then apply it again during rotation
    if let presentingView = presentingViewController.view {
      presentingView.layer.transform = CATransform3DIdentity
    }

    coordinator.animate(alongsideTransition: { [weak self] (context) in
      if let presentingView = self?.presentingViewController.view {
        presentingView.layer.transform = self?.calculatePerspectiveTransform() ?? CATransform3DIdentity
      }
    })
  }