View Controller Transition实现京东加购物车效果

这篇文章中我们主要来叙述一下上述动画效果的实现方案。主要涉及 View Controller 转场动画的知识。

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Presenting a View Controller

显示一个 View Controller 主要有一下几种方式：

• 使用 segues 自动显示 View Controller；
• 使用 showViewController:sender: 和 showDetailViewController:sender: 方法显示 View Controller；
• 调用 presentViewController:animated:completion: 方法依模态形式显示 View Controller

通过上述方式，我们可以将一个 View Controller 显示出来，而对于显示地形式，我们可以使用 UIKit 中预定义的形式，也可以自定义（即自定义转场动画）。

Customizing the Transition Animations

自定义转场动画中，主要包含以下几个组件：

• Presenting View Controller（正在显示的 View Controller）
• Animator（动画管理者）
• Presented View Controller（要显示的 View Controller）
• Transitioning Delegate Object（转场代理，用来提供 Animator 对象）

实现自定义转场动画，通常按照以下几个步骤来完成

• 创建 Presented View Controller；
• 创建 Animator；
• 设置 Presented View Controller 的 transitioningDelegate 属性，并实现 UIViewControllerTransitioningDelegate 提供 Animator 对象；
• 在 Presenting View Controller 中调用 presentViewController:animated:completion: 显示 Presented View Controller；

Presented View Controller

这里，我们将 Presented View Controller 本身作为其转场代理，你也可以使用单独的代理对象。

class PresentedViewController: UIViewController {
 let imageView = UIImageView(image: UIImage(named: "jd_add.jpg"))
 override func viewDidLoad() {
  super.viewDidLoad()
  // 1.设置 transitioningDelegate（转场代理）
  transitioningDelegate = self
  modalPresentationStyle = .custom
  view.addSubview(imageView)
 }
 override func viewDidLayoutSubviews() {
  super.viewDidLayoutSubviews()
  imageView.frame = CGRect(x: 0, y: 120, width: UIScreen.main.bounds.width, height: UIScreen.main.bounds.height - 120)
 }
 override func touchesBegan(_ touches: Set, with event: UIEvent?) {
  self.dismiss(animated: true, completion: nil)
 }
}

Animator

Animator 作为转场动画的管理者，主要负责 Presenting 和 Dismissing 动画效果。

动画时长

/// 转场动画时长
func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
 return TimeInterval(0.5)
}

执行动画

/// 执行转场动画
func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
 switch type {
 case .Present:
  present(transitionContext: transitionContext)
 case .Dismiss:
  dismiss(transitionContext: transitionContext)
 }
}

Presenting 动画

/// Presenting 动画
func present(transitionContext: UIViewControllerContextTransitioning) {
 /** 1.从转场上下文中取出 Presenting/Pressented View Controller 及容器视图 */
 guard let presentingVC = transitionContext.viewController(forKey: .from) as? ViewController else {
  return
 }
 guard let presentedVC = transitionContext.viewController(forKey: .to) as? PresentedViewController else {
  return
 }
 let containerView = transitionContext.containerView
 /** 2.设置 Presenting View Controller 所显示内容的属性 */
 // 对 presentingVC 的视图内容截屏，用于 presentedVC 显示出来时的背景
 guard let presentingVCViewSnapshot = presentingVC.view.snapshotView(afterScreenUpdates: false) else {
  return
 }
 // 隐藏 presentingVC 的 view，并将其截屏添加到 containerView 中
 presentingVC.view.isHidden = true
 containerView.addSubview(presentingVCViewSnapshot)
 // 改变 presentingVCViewSnapshot 的焦点
 presentingVCViewSnapshot.layer.anchorPoint = CGPoint(x: 0.5, y: 1)
 // 更新 presentingVCViewSnapshot 的 frame
 presentingVCViewSnapshot.frame = presentingVC.view.frame
 /** 3.设置 Presented View Controller 所显示内容的属性 */
 presentedVC.view.frame = CGRect(x: 0, y: containerView.bounds.height, width: containerView.bounds.width, height: containerView.bounds.height)
 containerView.addSubview(presentedVC.view)
 /** 4.设置 Presenting 转场动画 */
 UIView.animate(withDuration: transitionDuration(using: transitionContext), animations: {
  // 改变 presentingVCViewSnapshot 的 layer 的 transform，使其绕 X轴 旋转，并改变大小
  presentingVCViewSnapshot.layer.transform.m34 = -1 / 100.0
  presentingVCViewSnapshot.layer.transform = presentingVCViewSnapshot.layer.transform = CATransform3DConcat(CATransform3DMakeRotation(CGFloat(0.1), 1, 0, 0), CATransform3DMakeScale(0.85, 0.95, 1))
  // 改变 presentedVC 的 view 的 transform
  presentedVC.view.transform = CGAffineTransform(translationX: 0, y: -containerView.bounds.height)
 }) { (finished) in
  // 告知 UIKit Presenting 转场动画结束（很重要）
  transitionContext.completeTransition(true)
 }
}

Dismissing 动画

/// Dismissing 动画
func dismiss(transitionContext: UIViewControllerContextTransitioning) {
 /** 1.从转场上下文中取出容器视图、Presenting/Pressented View Controller 及其 view 的截屏 */
 let containerView = transitionContext.containerView
 guard let presentingVC = transitionContext.viewController(forKey: .from) as? PresentedViewController else {
  return
 }
 guard let presentedVC = transitionContext.viewController(forKey: .to) as? ViewController else {
  return
 }
 let subviewsCount = containerView.subviews.count
 let presentedVCViewSnapshot = containerView.subviews[subviewsCount - 2]
 /** 2.设置 Dismissing 转场动画 */
 UIView.animate(withDuration: transitionDuration(using: transitionContext), animations: {
  // 将 presentedVCViewSnapshot 的 transform 恢复到初始值
  presentedVCViewSnapshot.layer.transform = CATransform3DIdentity
  // 将 presentedVC 的 view 的 transform 恢复到初始值
  presentingVC.view.transform = CGAffineTransform.identity
 }) { (finished) in
  // 使 presentedVC 的 view 显示出来，并隐藏其截屏
  presentedVC.view.isHidden = false
  presentedVCViewSnapshot.removeFromSuperview()
  // 告知 UIKit Dismissing 转场动画结束（很重要）
  transitionContext.completeTransition(true)
 }
}

Transitioning Delegate

// MARK: - 2.实现 UIViewControllerTransitioningDelegate 提供 Animator
extension PresentedViewController: UIViewControllerTransitioningDelegate {
 /// Present
 func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
  return MyAnimator(type: .Present)
 }
 /// Dismiss
 func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
  return MyAnimator(type: .Dismiss)
 }
}
Present
@IBAction func present() {
 let presentedVC = PresentedViewController()
 present(presentedVC, animated: true, completion: nil)
}

关于 View Controller Transition 就介绍到这里，你应该熟悉了其使用方法，至于博客中的动画效果，我想就没办法深究了，这是一个花费时间苦差事。如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对我们网站的支持！