在iOS7之前，开发者为了寻求自定义Navigation Controller的Push/Pop动画，只能受限于子类化一个UINavigationController，或是用自定义的动画去覆盖它。但是随着iOS7的到来，Apple针对开发者推出了新的工具，以更灵活地方式管理UIViewController切换。
我把最终的Demo稍做修改，算是找了一个合适的应用场景，另外配上几张美图，拉拉人气
。
虽然是Swift的Demo，但是转成Objective-C相当容易。
最终效果预览：
自定义导航栏的Push/Pop动画
为了在基于UINavigationController下做自定义的动画切换，先建立一个简单的工程，这个工程的rootViewController是一个UINavigationController，UINavigationController的rootViewController是一个简单的UIViewController（称之为主页面），通过这个UIViewController上的一个Button能进入到下一个UIViewController中（称之为详情页面），我们先在主页面的ViewController上实现两个协议：UINavigationControllerDelegate和UIViewControllerAnimatedTransitioning，然后在ViewDidLoad里面把navigationController的delegate设为self，这样在导航栏Push和Pop的时候我们就知道了，然后用一个属性记下是Push还是Pop，就像这样：
func navigationController(navigationController: UINavigationController!, animationControllerForOperation operation: UINavigationControllerOperation, fromViewController fromVC: UIViewController!, toViewController toVC: UIViewController!) -> UIViewControllerAnimatedTransitioning! {
navigationOperation = operation
return self
}
这是iOS7的新方法，这个方法需要你提供一个UIViewControllerAnimatedTransitioning，那UIViewControllerAnimatedTransitioning到底是什么呢？
UIViewControllerAnimatedTransitioning是苹果新增加的一个协议，其目的是在需要使用自定义动画的同时，又不影响视图的其他属性，让你把焦点集中在动画实现的本身上，然后通过在这个协议的回调里编写自定义的动画代码，即“切换中应该会发生什么”，负责切换的具体内容，任何实现了这一协议的对象被称之为动画控制器。你可以借助协议能被任何对象实现的这一特性，从而把各种动画效果封装到不同的类中，只要方便使用和管理，你可以发挥一切手段。我在这里让主页面实现动画控制器也是可以的，因为它是导航栏的rootViewController，会一直存在，我只要在里面编写自定义的Push和Pop动画代码就可以了：
//UIViewControllerTransitioningDelegate
func transitionDuration(transitionContext: UIViewControllerContextTransitioning!) -> NSTimeInterval {
return 0.4
}
func animateTransition(transitionContext: UIViewControllerContextTransitioning!) {
let containerView = transitionContext.containerView()
let toViewController = transitionContext.viewControllerForKey(UITransitionContextToViewControllerKey)
let fromViewController = transitionContext.viewControllerForKey(UITransitionContextFromViewControllerKey)
var destView: UIView!
var destTransform: CGAffineTransform!
if navigationOperation == UINavigationControllerOperation.Push {
containerView.insertSubview(toViewController.view, aboveSubview: fromViewController.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: fromViewController.view)
destView = fromViewController.view
// 如果IDE是Xcode6 Beta4+iOS8SDK，那么在此处设置为0，动画将不会被执行(不确定是哪里的Bug)
destTransform = CGAffineTransformMakeScale(0.1, 0.1)
}
UIView.animateWithDuration(transitionDuration(transitionContext), animations: {
destView.transform = destTransform
}, completion: ({completed in
transitionContext.completeTransition(true)
}))
}
上面第一个方法返回动画持续的时间，而下面这个方法才是具体需要实现动画的地方。UIViewControllerAnimatedTransitioning的协议都包含一个对象：transitionContext，通过这个对象能获取到切换时的上下文信息，比如从哪个VC切换到哪个VC等。我们从transitionContext获取containerView，这是一个特殊的容器，切换时的动画将在这个容器中进行；UITransitionContextFromViewControllerKey和UITransitionContextToViewControllerKey就是从哪个VC切换到哪个VC，容易理解；除此之外，还有直接获取view的UITransitionContextFromViewKey和UITransitionContextToViewKey等。
我按Push和Pop把动画简单的区分了一下，Push时scale由小变大，Pop时scale由大变小，不同的操作，toViewController的视图层次也不一样。最后，在动画完成的时候调用completeTransition，告诉transitionContext你的动画已经结束，这是非常重要的方法，必须调用。在动画结束时没有对containerView的子视图进行清理（比如把fromViewController的view移除掉）是因为transitionContext会自动清理，所以我们无须在额外处理。
注意一点，这样一来会发现原来导航栏的交互式返回效果没有了，如果你想用原来的交互式返回效果的话，在返回动画控制器的delegate方法里返回nil，如：
if operation == UINavigationControllerOperation.Push {
navigationOperation = operation
return self
}
return nil
一个简单的自定义导航栏Push/Pop动画就完成了。
自定义Modal的Present/Dismiss动画
func transitionDuration(transitionContext: UIViewControllerContextTransitioning!) -> NSTimeInterval {
return 0.6
}
func animateTransition(transitionContext: UIViewControllerContextTransitioning!) {
let containerView = transitionContext.containerView()
let toViewController = transitionContext.viewControllerForKey(UITransitionContextToViewControllerKey)
let fromViewController = transitionContext.viewControllerForKey(UITransitionContextFromViewControllerKey)
var destView: UIView!
var destTransfrom = CGAffineTransformIdentity
let screenHeight = UIScreen.mainScreen().bounds.size.height
if modalPresentingType == ModalPresentingType.Present {
destView = toViewController.view
destView.transform = CGAffineTransformMakeTranslation(0, screenHeight)
containerView.addSubview(toViewController.view)
} else if modalPresentingType == ModalPresentingType.Dismiss {
destView = fromViewController.view
destTransfrom = CGAffineTransformMakeTranslation(0, screenHeight)
containerView.insertSubview(toViewController.view, belowSubview: fromViewController.view)
}
UIView.animateWithDuration(transitionDuration(transitionContext), delay: 0, usingSpringWithDamping: 0.6, initialSpringVelocity: 0,
options: UIViewAnimationOptions.CurveLinear, animations: {
destView.transform = destTransfrom
}, completion: {completed in
transitionContext.completeTransition(true)
})
}
func animationControllerForPresentedController(presented: UIViewController!, presentingController presenting: UIViewController!, sourceController source: UIViewController!) -> UIViewControllerAnimatedTransitioning! {
modalPresentingType = ModalPresentingType.Present
return self
}
func animationControllerForDismissedController(dismissed: UIViewController!) -> UIViewControllerAnimatedTransitioning! {
modalPresentingType = ModalPresentingType.Dismiss
return self
}
override func prepareForSegue(segue: UIStoryboardSegue!, sender: AnyObject!) {
let modal = segue.destinationViewController as UIViewController
modal.transitioningDelegate = self
}
自定义导航栏的交互式动画
使用UIPercentDrivenInteractiveTransition
实际上这个类就是实现了UIViewControllerInteractiveTransitioning协议的交互控制器，我们使用它就能够轻松地为动画控制器添加一个交互动画。调用updateInteractiveTransition:更新进度；调用cancelInteractiveTransition取消交互，返回到切换前的状态；调用finishInteractiveTransition通知上下文交互已完成，同completeTransition一样。我们把交互动画应用到详情页面Back回主页面的地方，由于之前的动画管理器的角色是主页面担任的，Navigation Controller的delegate同一时间只能有一个，那在这里交互控制器的角色也由主页面来担任。首先添加一个手势识别器：
let popRecognizer = UIScreenEdgePanGestureRecognizer(target: self, action: Selector("handlePopRecognizer:"))
popRecognizer.edges = UIRectEdge.Left
self.navigationController.view.addGestureRecognizer(popRecognizer)
func handlePopRecognizer(popRecognizer: UIScreenEdgePanGestureRecognizer) {
var progress = popRecognizer.translationInView(navigationController.view).x / navigationController.view.bounds.size.width
progress = min(1.0, max(0.0, progress))
println("\(progress)")
if popRecognizer.state == UIGestureRecognizerState.Began {
println("Began")
self.interactivePopTransition = UIPercentDrivenInteractiveTransition()
self.navigationController.popViewControllerAnimated(true)
} else if popRecognizer.state == UIGestureRecognizerState.Changed {
self.interactivePopTransition?.updateInteractiveTransition(progress)
println("Changed")
} else if popRecognizer.state == UIGestureRecognizerState.Ended || popRecognizer.state == UIGestureRecognizerState.Cancelled {
if progress > 0.5 {
self.interactivePopTransition?.finishInteractiveTransition()
} else {
self.interactivePopTransition?.cancelInteractiveTransition()
}
println("Ended || Cancelled")
self.interactivePopTransition = nil
}
}
现在我们已经有了交互控制器对象，只需要把它给告知给Navigation Controller就行了，我们实现UINavigationControllerDelegate的另一个方法：
func navigationController(navigationController: UINavigationController!, interactionControllerForAnimationController animationController: UIViewControllerAnimatedTransitioning!) -> UIViewControllerInteractiveTransitioning! {
return self.interactivePopTransition
}
我们从详情页面通过自定义的交互动画返回到上一个页面的工作就完成了。
Demo效果预览：
使用UIPercentDrivenInteractiveTransition的Demo
自定义交互控制器
func startInteractiveTransition(transitionContext: UIViewControllerContextTransitioning!) {
self.transitionContext = transitionContext
let containerView = transitionContext.containerView()
let toViewController = transitionContext.viewControllerForKey(UITransitionContextToViewControllerKey)
let fromViewController = transitionContext.viewControllerForKey(UITransitionContextFromViewControllerKey)
containerView.insertSubview(toViewController.view, belowSubview: fromViewController.view)
self.transitingView = fromViewController.view
}
func updateWithPercent(percent: CGFloat) {
let scale = CGFloat(fabsf(Float(percent - CGFloat(1.0))))
transitingView?.transform = CGAffineTransformMakeScale(scale, scale)
transitionContext?.updateInteractiveTransition(percent)
}
func finishBy(cancelled: Bool) {
if cancelled {
UIView.animateWithDuration(0.4, animations: {
self.transitingView!.transform = CGAffineTransformIdentity
}, completion: {completed in
self.transitionContext!.cancelInteractiveTransition()
self.transitionContext!.completeTransition(false)
})
} else {
UIView.animateWithDuration(0.4, animations: {
print(self.transitingView)
self.transitingView!.transform = CGAffineTransformMakeScale(0, 0)
print(self.transitingView)
}, completion: {completed in
self.transitionContext!.finishInteractiveTransition()
self.transitionContext!.completeTransition(true)
})
}
}
func handlePopRecognizer(popRecognizer: UIScreenEdgePanGestureRecognizer) {
var progress = popRecognizer.translationInView(navigationController.view).x / navigationController.view.bounds.size.width
progress = min(1.0, max(0.0, progress))
println("\(progress)")
if popRecognizer.state == UIGestureRecognizerState.Began {
println("Began")
isTransiting = true
//self.interactivePopTransition = UIPercentDrivenInteractiveTransition()
self.navigationController.popViewControllerAnimated(true)
} else if popRecognizer.state == UIGestureRecognizerState.Changed {
//self.interactivePopTransition?.updateInteractiveTransition(progress)
updateWithPercent(progress)
println("Changed")
} else if popRecognizer.state == UIGestureRecognizerState.Ended || popRecognizer.state == UIGestureRecognizerState.Cancelled {
//if progress > 0.5 {
// self.interactivePopTransition?.finishInteractiveTransition()
//} else {
// self.interactivePopTransition?.cancelInteractiveTransition()
//}
finishBy(progress < 0.5)
println("Ended || Cancelled")
isTransiting = false
//self.interactivePopTransition = nil
}
}
func navigationController(navigationController: UINavigationController!, interactionControllerForAnimationController animationController:
UIViewControllerAnimatedTransitioning!) -> UIViewControllerInteractiveTransitioning! {
if !self.isTransiting {
return nil
}
return self
}
最终效果:
@availability(iOS, introduced=7.0)
func snapshotViewAfterScreenUpdates(afterUpdates: Bool) -> UIView
