閱讀源碼后可以發(fā)現(xiàn)妆丘，和一般自定義轉(zhuǎn)場動畫一致鲜漩，新建繼承 NSObject 子類徘禁，遵守 UIViewControllerAnimatedTransitioning 協(xié)議疾渴。

實(shí)現(xiàn)兩個(gè)代理方法:

• 返回動畫持續(xù)時(shí)間代理:

func transitionDuration(transitionContext: UIViewControllerContextTransitioning?) -> NSTimeInterval {
        return 0.75
}

• 自定義動畫代理:

func animateTransition(transitionContext: UIViewControllerContextTransitioning) {    
      // 自定義動畫函數(shù)
}

參數(shù) transitionContext 可以可以通過 func viewForKey(key: String) -> UIView? / public func viewControllerForKey(key: String) -> UIViewController? 取出轉(zhuǎn)場動畫的對應(yīng) fromView/toView / formViewController/toViewController 對應(yīng)的 key 值:

viewForKey:
UITransitionContextFromViewKey
UITransitionContextToViewKey

viewControllerForKey:
UITransitionContextFromViewControllerKey
UITransitionContextToViewControllerKey

在 Explode 動畫中主要在于屏幕快照的獲取以及快照的區(qū)域分剪，核心代碼:

// 獲取 fromView 的快照
let fromViewSnapshot = fromView.snapshotViewAfterScreenUpdates(false)

        // 將快照剪切成小塊加到 containerView 上
        for x in 0.0.stride(to: Double(size.width), by: Double(size.width / xFactor)) {
            for y in 0.0.stride(to: Double(size.height), by: Double(size.height / yFactor)) {
                let snapshotRegion = CGRect(x: CGFloat(x), y: CGFloat(y), width: size.width / xFactor, height: size.height / yFactor)

                // 按所給區(qū)域獲得快照的小塊
                let snapshot = fromViewSnapshot.resizableSnapshotViewFromRect(snapshotRegion, afterScreenUpdates: false, withCapInsets: UIEdgeInsetsZero)
                // 主要是設(shè)置位置
                snapshot.frame = snapshotRegion
                // 將拼成的 fromView 快照加到 containerView的最頂層
                containerView.addSubview(snapshot)
                snapshots.append(snapshot)
            }
        }

// 將 fromView 隱藏
containerView.sendSubviewToBack(fromView)

剩下的就是對 每一個(gè)小塊的動畫處理屯仗，并在動畫結(jié)束后調(diào)用:

ransitionContext.completeTransition(!transitionContext.transitionWasCancelled())

這都很簡單搞坝，難的是如何結(jié)合手勢使用，這是最值得學(xué)習(xí)的地方魁袜，理解不深桩撮，可以 clone 源碼 學(xué)習(xí)敦第。

實(shí)現(xiàn)過程主要是對 UIPercentDrivenInteractiveTransition 的學(xué)習(xí)使用，和 IBAnimatable 的實(shí)現(xiàn)不同店量，我們采用 NavigationController 管理界面芜果，在 FirstViewController 的 func viewWillAppear(animated: Bool) {} 內(nèi)設(shè)置代理: navigationController?.delegate = self
(如果在方法: func viewDidLoad() {} 設(shè)置代理會導(dǎo)致轉(zhuǎn)場取消后無法再次進(jìn)行自定義動畫轉(zhuǎn)場)
實(shí)現(xiàn)代理方法:

extension FirstViewController: UINavigationControllerDelegate {
    func navigationController(navigationController: UINavigationController, animationControllerForOperation operation: UINavigationControllerOperation, fromViewController fromVC: UIViewController, toViewController toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        if operation == UINavigationControllerOperation.Push {
            // ExplodeAnimator 即為自定義的轉(zhuǎn)場動畫
            return ExplodeAnimator()
        } else {
            return nil
        }
    }
}

之后就是對 SecondViewController 內(nèi)進(jìn)行自定義手勢 popViewController :
首先對 view 添加返回手勢:

view.addGestureRecognizer({
            let pan = UIScreenEdgePanGestureRecognizer(target: self, action: #selector(SecondViewController.pan(_:)))
            pan.edges = UIRectEdge.Left
            return pan
        }())

手勢回調(diào)方法:

func pan(edgePan: UIScreenEdgePanGestureRecognizer) {

        let progress = edgePan.translationInView(self.view).x / self.view.bounds.width

        if edgePan.state == UIGestureRecognizerState.Began {
            self.percentDrivenTransition = UIPercentDrivenInteractiveTransition()
            self.navigationController?.popViewControllerAnimated(true)
        } else if edgePan.state == UIGestureRecognizerState.Changed {
            self.percentDrivenTransition?.updateInteractiveTransition(progress)
        } else if edgePan.state == UIGestureRecognizerState.Cancelled || edgePan.state == UIGestureRecognizerState.Ended {
            if progress > 0.5 {
                self.percentDrivenTransition?.finishInteractiveTransition()
            } else {
                self.percentDrivenTransition?.cancelInteractiveTransition()
            }
            self.percentDrivenTransition = nil
        }
    }

同樣，在 SecondViewController 的 func viewWillAppear(animated: Bool) {} 方法內(nèi)設(shè)置代理: navigationController!.delegate = self融师，區(qū)別只是在于多實(shí)現(xiàn)一個(gè)代理方法:

extension SecondViewController: UINavigationControllerDelegate {

    func navigationController(navigationController: UINavigationController, animationControllerForOperation operation: UINavigationControllerOperation, fromViewController fromVC: UIViewController, toViewController toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        if operation == UINavigationControllerOperation.Pop {
            return ExplodeAnimator()
        } else {
            return nil
        }
    }

    func navigationController(navigationController: UINavigationController, interactionControllerForAnimationController animationController: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning? {
        if animationController is ExplodeAnimator {
            return self.percentDrivenTransition
        } else {
            return nil
        }
    }
}

大功告成右钾，
效果展示:

Demo