最近在学swift，就用swift写了个小Demo[https://github.com/jiaowoxiaoming/CustomNavigaitonAnimations ]。
在项目中常常看见别的App不是用的原生的Push/Pop动画，都是怎么做的呢。iOS7之后，苹果就为我们做好接口了，让我们能灵活的控制UIViewController的切换。
言归正传，从零开始做一个转场动画。

从创建自定义Push/Pop说起

首先创建工程，storyBoard中拖一个ViewController，给它加上导航控制器。完毕之后，需要考虑动画的实现方式，恩，用transform动画吧。很简单的放大缩小动画。
因为我们需要自定义动画，所以需要实现UINavigationControllerDelegate协议方法。具体方法如下：

 func navigationController(navigationController: UINavigationController, animationControllerForOperation operation: UINavigationControllerOperation, fromViewController fromVC: UIViewController, toViewController toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        //这里用到了一个属性来记录当前操作的类型（Push or Pop）
        navigationOperation = operation
       
        return self
        
    }

在这里再赘述一下UINavigationControllerDelegate其他协议方法（已经了解的当我没说）

//这个方法就是切换横竖屏时调用的操作 设置方法设置导航控制器支持的设备方向
   @available(iOS 7.0, *)
    optional public func navigationControllerSupportedInterfaceOrientations(navigationController: UINavigationController) -> UIInterfaceOrientationMask
//这个方法设置导航控制器的首选设备方向
    @available(iOS 7.0, *)
    optional public func navigationControllerPreferredInterfaceOrientationForPresentation(navigationController: UINavigationController) -> UIInterfaceOrientation
 //下面两个方法可以对导航的转场动画进行设置 1.交互式动画 2.传统的push/pop 动画
    @available(iOS 7.0, *)
    optional public func navigationController(navigationController: UINavigationController, interactionControllerForAnimationController animationController: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning?
    
    @available(iOS 7.0, *)
    optional public func navigationController(navigationController: UINavigationController, animationControllerForOperation operation: UINavigationControllerOperation, fromViewController fromVC: UIViewController, toViewController toVC: UIViewController) -> UIViewControllerAnimatedTransitioning?

然后控制器需要实现另外一个协议UIViewControllerAnimatedTransitioning它有三个方法：

 // 动画时间
    public func transitionDuration(transitionContext: UIViewControllerContextTransitioning?) -> NSTimeInterval
 // 具体动画操作
    public func animateTransition(transitionContext: UIViewControllerContextTransitioning)
 //动画结束的回调方法
    optional public func animationEnded(transitionCompleted: Bool)

需要实现animateTransition和transitionDuration

func animateTransition(transitionContext: UIViewControllerContextTransitioning) {
       
        let containerView = transitionContext.containerView()
        
        let toViewController = transitionContext.viewControllerForKey(UITransitionContextToViewControllerKey)
        
        let fromeViewController = transitionContext.viewControllerForKey(UITransitionContextFromViewControllerKey)
        
        var destView:UIView!
        
        var destTransform:CGAffineTransform!
        
        if navigationOperation == UINavigationControllerOperation.Push {
            containerView?.insertSubview((toViewController?.view)!, aboveSubview: (fromeViewController?.view)!)
            destView = toViewController?.view
            
            destView.transform = CGAffineTransformMakeScale(0.1, 0.1)
            
            destTransform = CGAffineTransformMakeScale(1, 1)
            
        }
        else if navigationOperation == UINavigationControllerOperation.Pop
        {
            containerView?.insertSubview((toViewController?.view)!, belowSubview: (fromeViewController?.view)!)
            
            destView = fromeViewController?.view
            
            destTransform = CGAffineTransformMakeScale(0.1, 0.1)
            
        }
       
        UIView .animateWithDuration(transitionDuration(transitionContext), animations: { 
            destView.transform = destTransform!
            }, completion: ({completed in
                transitionContext.completeTransition(true)
            }))
    }

到此一个自定义的导航转场动画就完成了，至于具体的动画，在此我只是抛砖引玉，大家完全可以写出更绚丽的动画。