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 Animatorextension 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网站的支持！