关于自定义转场效果（transitioningDelegate）

第一种：没有动画效果跳转

效果图：

无动画效果.gif

从 AViewController -> BViewController

@objc func toBViewController() {
    let bVC = BViewController()
    // 注意：设置目标控制器 transition 转场效果代理. self: AViewController
    bVC.transitioningDelegate = self
    self.present(bVC, animated: true, completion: nil)
 }

// MARK: - UIViewControllerTransitioningDelegate
extension HomeViewController: UIViewControllerTransitioningDelegate {
    func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return self
    }
    
    func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return self
    }
}

// MARK: - UIViewControllerAnimatedTransitioning 关于取消 present 效果跳转(无动画效果)
extension HomeViewController: UIViewControllerAnimatedTransitioning {
    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return 0.5
    }
    
    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        // 关于取消 present 效果跳转(无动画效果)
        guard let toView = transitionContext.view(forKey: .to) else {
            transitionContext.completeTransition(true)
            return
        }
        transitionContext.containerView.addSubview(toView)
        transitionContext.completeTransition(true)
    }
}

第二种：类似 push、pop动画效果跳转

效果图：

类似 push/pop效果.gif

从 AViewController -> BViewController

enum TransitionType {
    case present
    case dismiss
}

@objc func toBViewController() {
    let bVC = BViewController()
    // 注意：设置目标控制器 transition 转场效果代理. self: AViewController
    bVC.transitioningDelegate = self
    self.present(bVC, animated: true, completion: nil)
 }

// MARK: - UIViewControllerTransitioningDelegate
extension HomeViewController: UIViewControllerTransitioningDelegate {
    func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        self.type = .present
        return self
    }
    
    func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        self.type = .dismiss
        return self
    }
}

// MARK: - UIViewControllerAnimatedTransitioning 关于自定义转场动效（push / pop 效果，push：从右->左；pop：从左->右）
extension HomeViewController: UIViewControllerAnimatedTransitioning {
    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return 0.5
    }
    
    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        guard let toView = transitionContext.view(forKey: .to),
              let fromView = transitionContext.view(forKey: .from) else {
            transitionContext.completeTransition(true)
            return
        }
        // 呈现在当前屏幕上的 vc 则为 from；目标 vc 则为to
        
        switch self.type {
        case .present:
            transitionContext.containerView.addSubview(toView)
            toView.transform = CGAffineTransform(translationX: self.view.bounds.width, y: 0)
            
            UIView.animate(withDuration: transitionDuration(using: nil)) {
                toView.transform = .identity
            } completion: { _ in
                transitionContext.completeTransition(true)
            }
        case .dismiss:
            // 将 toView 放置最底层，fromView平移后，就会看到 toview；如果直接 add toView，则效果会一闪，看不到 fromView 平移效果。原因：add toView 后被 toView 遮住了。
            // 因此使用 insertSubview
            transitionContext.containerView.insertSubview(toView, at: 0)
            UIView.animate(withDuration: transitionDuration(using: nil)) {
                fromView.transform = CGAffineTransform(translationX: self.view.bounds.width, y: 0)
            } completion: { _ in
                transitionContext.completeTransition(true)
            }
        }
    }
}

第三种：类似 淘宝展示商品 动画效果跳转

效果图：

商品.gif

@objc func toBViewController() {
    let bVC = BViewController()
    // 注意：设置目标控制器 transition 转场效果代理. self: AViewController
    bVC.transitioningDelegate = self
    bVC.view.frame = CGRect(x: 0, y: self.view.bounds.height - detailViewHeight, width: self.view.bounds.width, height: detailViewHeight)
    self.present(bVC, animated: true, completion: nil)
 }
    
 @objc func tapFromView() {
    self.dismiss(animated: true, completion: nil)
 }

// MARK: - UIViewControllerTransitioningDelegate
extension HomeViewController: UIViewControllerTransitioningDelegate {
    func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        self.type = .present
        return self
    }
    
    func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        self.type = .dismiss
        return self
    }
}

// MARK: - UIViewControllerAnimatedTransitioning 关于淘宝展示商品信息效果转场效果
extension HomeViewController: UIViewControllerAnimatedTransitioning {
   func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
       return 1
   }

   func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        // 关于取消 present 效果跳转(无动画效果)
        guard let toView = transitionContext.view(forKey: .to),
              let fromView = transitionContext.view(forKey: .from) else {
            transitionContext.completeTransition(true)
            return
        }

        switch self.type {
        case .present:
            transitionContext.containerView.addSubview(toView)
            // 设置商品 VC 效果
            var transition3D = CATransform3DIdentity
            // CATransform3D 的 m34 元素，用来做透视(有 3D 效果);
            // m34 为-1.0 / d 来应用透视效果; d = 通常500~1000
            // 注意：得先设置
            transition3D.m34 = -1 / 1000
            // 绕 x 轴3D旋转 pi/5
            transition3D = CATransform3DRotate(transition3D, .pi / 8, 1, 0, 0)
            // 防止 fromView 旋转后遮住 toView; fromView平移(z轴方向)
            transition3D = CATransform3DTranslate(transition3D, 0, 0, -200)

            UIView.animate(withDuration: transitionDuration(using: nil)) {
                fromView.layer.transform = transition3D
            } completion: { _ in
                // 再进行缩放
                UIView.animate(withDuration: self.transitionDuration(using: nil)) {
                    fromView.layer.transform = CATransform3DMakeScale(0.9, 0.9, 1)
                }
            }

            // toView 动画
            toView.transform = CGAffineTransform(translationX: 0, y: toView.bounds.height)
            UIView.animate(withDuration: transitionDuration(using: nil)*2) {
                toView.transform = .identity
            } completion: { _ in
                // 由于 completeTransition 后会出现 fromView 被移除，因此需要截图 代替 fromView

                UIGraphicsBeginImageContextWithOptions(self.view.bounds.size, false, 0)
                // 截取当前屏幕
                self.view.drawHierarchy(in: self.view.bounds, afterScreenUpdates: false)
                // 截取的当前UIView转成UIImage
                let image = UIGraphicsGetImageFromCurrentImageContext()
                UIGraphicsEndImageContext()

                let replaceImageView = UIImageView(image: image)
                replaceImageView.isUserInteractionEnabled = true
                replaceImageView.transform = CGAffineTransform(scaleX: 0.9, y: 0.9)

                let tap = UITapGestureRecognizer(target: self, action: #selector(self.tapFromView))
                replaceImageView.addGestureRecognizer(tap)


                transitionContext.containerView.insertSubview(replaceImageView, at: 0)
                transitionContext.completeTransition(true)
            }

        case .dismiss:
            transitionContext.containerView.addSubview(fromView)
            UIView.animate(withDuration: transitionDuration(using: nil)) {
                fromView.transform = CGAffineTransform(translationX: 0, y: fromView.bounds.height)
            } completion: { _ in
                UIView.animate(withDuration: self.transitionDuration(using: nil)*0.5) {
                    toView.transform = .identity
                }
                transitionContext.completeTransition(true)
            }
        }
   }
}