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UINavigationController内部页面跳转默认为左右切换，但是当我们想向上弹出进入界面，或者向下离开界面时，需要实现UINavigationControllerDelegate 协议自行控制页面的动画(否则直接在navVc上叠加动画会导致动画结束后的那个页面，自动加了异常动画)，本文介绍这个实现方案。

定义一个类实现 UIViewControllerAnimatedTransitioning协议，实现下面的函数：

class NavigationControllerAnimation: NSObject, UIViewControllerAnimatedTransitioning {let operation: UINavigationController.Operationinit(operation: UINavigationController.Operation) {self.operation = operationsuper.init()}//页面过渡动画时间 func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {return 0.3}//加页面过渡的动画public func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {guard let fromViewController = transitionContext.viewController(forKey: UITransitionContextViewControllerKey.from),let toViewController = transitionContext.viewController(forKey: UITransitionContextViewControllerKey.to) else { return }let containerView = transitionContext.containerViewif operation == .push {// do your animation for pushtoViewController.view.frame = containerView.bounds.offsetBy(dx: 0, dy: containerView.frame.size.height)fromViewController.view.frame = containerView.boundscontainerView.addSubview(toViewController.view)UIView.animate(withDuration: transitionDuration(using: transitionContext),delay: 0,options: [ UIView.AnimationOptions.curveEaseOut ],animations: {toViewController.view.frame = containerView.bounds},completion: { (finished) intransitionContext.completeTransition(true)})} else if operation == .pop {// do your animation for popcontainerView.addSubview(toViewController.view)containerView.addSubview(fromViewController.view)//containerView 上加的view在动画结束后一段时间后被释放了fromViewController.view.frame  = containerView.bounds
//            toViewController.view.frame = containerView.boundsUIView.animate(withDuration: transitionDuration(using: transitionContext),animations: {fromViewController.view.frame = containerView.bounds.offsetBy(dx: 0, dy: containerView.frame.size.height)},completion: { (finished) intransitionContext.completeTransition(true)})}}
}

UINavigationController 添加delegate

class BaseNavigationController: UINavigationController {override func viewDidLoad() {super.viewDidLoad()self.delegate = self}
}

实现delegate的协议 ，返回本文最开始定义的类的对象,这里只要返回nil 就会是默认的动画方式（所以可以按照需求切换界面过渡动画）

extension BaseNavigationController : UINavigationControllerDelegate {func navigationController(_ navigationController: UINavigationController, animationControllerFor operation: UINavigationController.Operation, from fromVC: UIViewController, to toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {return NavigationControllerAnimation(operation: operation)  }}

参考：
https://stackoverflow.com/questions/2215672/how-to-change-the-push-and-pop-animations-in-a-navigation-based-app