UINavigationController就一本書一樣，而UIViewController就是它的每一頁，我們可以一頁一頁的翻，也可以瞬間跳到某一頁，或者回歸的過去的某一頁。

構成

我們首先要有一個rootViewController，裝進UINavigationController。

例如在AppDelegate的didFinishLaunchingWithOptions中

let navVC = UINavigationController(rootViewController: ViewController())
window?.rootViewController = navVC
window?.backgroundColor = UIColor.gray
window?.makeKeyAndVisible()

用ViewController()創建一個UIViewController來初始化UINavigationController, 這樣ViewController()作為導航欄的第一頁顯示出來。

UINavigationController的組成， 引用一下官網的

UI元素除了UIViewController的數組外，還有navigationBar，toolbar。

接下里我們豐富一下，將其UI元素全部用上。

在ViewController的viewDidLoad中加入代碼

// 顯示toolbar
self.navigationController?.isToolbarHidden = false
self.setToolbarItems([UIBarButtonItem(barButtonSystemItem: .camera, target: nil, action: nil), UIBarButtonItem(barButtonSystemItem: .bookmarks, target: nil, action: nil)], animated: false)
    
// 設置navigationBar的title
self.title = "root view"
    
// 設置navigationBar按鈕
self.navigationItem.setLeftBarButton(UIBarButtonItem(barButtonSystemItem: .add, target: nil, action: nil), animated: false)
self.navigationItem.setRightBarButton(UIBarButtonItem(barButtonSystemItem: .done, target: nil, action: nil), animated: false)

注意：toolbar的items的設置，是與UIViewController關聯的，不要UINavigationController上setItems是不會顯示的

跳轉

Push

push就是將VC一個一個疊上去，默認行為是從右側進入

self.navigationItem.setRightBarButton(UIBarButtonItem(barButtonSystemItem: .done, target: self, action: #selector(self.pushAction(sender:))), animated: false)

func pushAction(sender:UIBarButtonItem) {
    self.navigationController?.pushViewController(ViewController2(), animated: true)
}    

我們將done按鈕加入push動作, 點擊done，從右到左進入，這時候系統會添加一個navigationBar item，用于pop到下層頁面，title就是下層頁面設置的title

push對應的返回接口是pop

self.navigationController?.popViewController(animated: true)

Present

說道跳轉，這里也提一下present，present跳到另外一個頁面，默認行為是從下而上，除了表現上與push不一樣

• 不是UINavigationController的管理范疇，UIViewController可直接present到其他頁面
• 同一個UIViewController不可以present兩次，但present起來的vc是可以再次present的
• present類似模態窗口，在這個窗口dissmiss前，交互只能在這個窗口做，之前的頁面不可交互和變化, 就仿佛你放下一本書，就拿起另外一本書，不能同時看兩本書

present對應的消失接口是dissmiss

self.dismiss(animated: true, completion: nil)

Show

8.0以后提供了show方法，這個是根據viewController所處容器，使用容器的跳轉行為，例如viewController所處容器為navigationController(viewController的容器還有splitViewController)，就和push一樣

open func show(_ vc: UIViewController, sender: Any?)

自定義跳轉方式（轉場動畫）

自定義轉場動畫，需要制定兩個因素

• 從哪個viewController跳轉到哪個viewController
• 動畫內容

自定義 Present

我們嘗試改寫present的動畫效果，它默認是由下而上，改成自上而下

func pushAction(sender:UIBarButtonItem) {
    let vc = ViewController2()
    vc.transitioningDelegate = self // 實現UIViewControllerTransitioningDelegate協議
    self.present(vc, animated: true, completion: nil)
}

實現UIViewControllerTransitioningDelegate協議, 下面就是用來實現，present和dismiss動畫的

@available(iOS 2.0, *)
optional public func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning?

    
@available(iOS 2.0, *)
optional public func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning?

這兩個接口需要返回id<UIViewControllerAnimatedTransitioning>

UIViewControllerAnimatedTransitioning

// 轉場時間
public func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval
// 動畫
public func animateTransition(using transitionContext: UIViewControllerContextTransitioning)

接下來需要創建一個id<UIViewControllerAnimatedTransitioning>的類，

class PresentAnimator: NSObject, UIViewControllerAnimatedTransitioning {
    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return 1
    }
    
    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        let fromViewController = transitionContext.viewController(forKey: UITransitionContextViewControllerKey.from)
        let toViewController = transitionContext.viewController(forKey: UITransitionContextViewControllerKey.to)
        let containerView = transitionContext.containerView
        
        // 將跳轉后的頁面，設置到屏幕上方
        toViewController?.view.frame = (fromViewController?.view.frame)!
        toViewController?.view.frame.origin.y -= (toViewController?.view.frame.height)!
        
        // 添加到轉場動畫容器上，
        containerView.addSubview((toViewController?.view)!)
        
        UIView.animate(withDuration: transitionDuration(using: transitionContext), animations: { () -> Void in
            // 回歸的屏幕位置
            toViewController?.view.frame = (fromViewController?.view.frame)!
        }, completion: { (complete:Bool) -> Void in
            transitionContext.completeTransition(true)
        })
    }
}

經過我打印地址研究，得出以下結論

• containerView是做動畫用的容器, 初始狀態是將跳轉前頁面(較為頂層的一個view，如果vc在navigationController中就是naviController的view)添加為自己的subview
• fromViewController不是跳轉前vc, 只是將跳轉前頁面添加為自己的subview，用來做舊頁面的退出動畫
• toViewController則是跳轉后vc，做新頁面的登臺動畫
• transitionDuration時間是提供給系統的，提供跳轉時系統的默認表現，自定義animate的時間最好和其保持一致
• containerView臨時產生，在動畫結束后，從UI上撤掉，但view的改變會遺留下來

注意：transitionContext.completeTransition(true)是必須要調用的，否則系統認為轉場為完成，第二頁不能進行任何交互

自定義 Dismiss

dismiss 與 present 類似，只是fromViewController變成了第二頁，toViewController變成了第一頁, 記住上述的那幾條結論來理解containerView.addSubview

class DismissAnimator: NSObject, UIViewControllerAnimatedTransitioning {
    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return 2
    }
    
    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        let fromViewController = transitionContext.viewController(forKey: UITransitionContextViewControllerKey.from)
        let toViewController = transitionContext.viewController(forKey: UITransitionContextViewControllerKey.to)
        let containerView = transitionContext.containerView
        containerView.addSubview((toViewController?.view)!)
        containerView.addSubview((fromViewController?.view)!)
        UIView.animate(withDuration: transitionDuration(using: transitionContext), animations: { () -> Void in
            fromViewController?.view.alpha = 0.0
        }, completion: { (complete:Bool) -> Void in
            transitionContext.completeTransition(true)
        })
    }
}

自定義 Push

只是掛接delegate的位置不同

// 自定義navigationController動畫
self.navigationController?.delegate = self

實現同樣和上面一樣，返回id<UIViewControllerAnimatedTransitioning>, 為了簡單，我們做之前present和dismiss一樣的動畫

func navigationController(_ navigationController: UINavigationController, animationControllerFor operation: UINavigationControllerOperation, from fromVC: UIViewController, to toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {
    if operation == .push {
        return PresentAnimator();
    } else {
        return DismissAnimator();
    }
}

交互式動畫

最后在說一個present的交互動畫

交互式動畫就隨手勢做的動畫，手拖的距離，來決定動畫執行的進度

需要再實現UIViewControllerTransitioningDelegate協議中的交互式接口，要求返回一個id<UIViewControllerInteractiveTransitioning>

optional public func interactionControllerForPresentation(using animator: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning?

    
optional public func interactionControllerForDismissal(using animator: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning?

這個交互式動畫，依賴于之前設置的動畫方式，只是用來設置百分比，這個百分比需要你自己不斷提供給他，一般用手勢來不斷調用id<UIViewControllerInteractiveTransitioning>的update接口，我們為了簡單，用timer來模擬

創建一個id<UIViewControllerInteractiveTransitioning>

class InteractiveAnimator: UIPercentDrivenInteractiveTransition {
    
}

viewController中加入屬性

var interactiveAnimator:InteractiveAnimator = InteractiveAnimator()
var timer:Timer? = nil
var times:CGFloat = 0;

修改接口

func interactionControllerForPresentation(using animator: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning?
{
    timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(self.timeUpdate), userInfo: nil, repeats: true);
    return interactiveAnimator
}
    
func interactionControllerForDismissal(using animator: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning?
{
    timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(self.timeUpdate), userInfo: nil, repeats: true);
    return interactiveAnimator
}

func timeUpdate() {
    times += 1
    if times <= 5 {
        let per:CGFloat = times/5
        interactiveAnimator.update(per)
    } else {
        timer?.invalidate()
        interactiveAnimator.finish()
    }
}

timeUpdate的會該5次百分比，這個動畫也分5下完成, 每秒變化一次。timeUpdate這是里timer來調用的，你可以用任意的交互方式來調用，百分比自己來計算

demo 地址 記得 pod install