類PageViewController也是一個特殊的UIViewController，它可以管理多個頁面，每個頁面都是一個UIViewController，可程序控制或者用戶手勢來切換頁面。

如下代碼，展示了PageViewController的使用：

    import UIKit
    class VCBase: UIViewController
    {
        
        var label : UILabel?
        override func viewDidLoad()
        {
            super.viewDidLoad()
            label = UILabel(frame: CGRect(x: 0, y: 0, width: view.frame.width, height: 200))
            label!.textAlignment = .center
            view.addSubview(label!)
            view.backgroundColor = UIColor.white
        }
    }
    class Page1: VCBase
    {
        override func viewDidLoad()
        {
            super.viewDidLoad()
            label!.text = "#1"
        }
    }
    class Page2: VCBase
    {
        override func viewDidLoad()
        {
            super.viewDidLoad()
            label!.text = "#2"
        }
    }
    class PageViewController :UIPageViewController,UIPageViewControllerDataSource{
        var vcs :[UIViewController]
        required init(){
            vcs = [Page1(),Page2()]
            super.init(transitionStyle: .scroll, navigationOrientation: .horizontal, options: nil)
        }
        required  init?(coder: NSCoder){
            fatalError()
        }
        override func viewDidLoad() {
            self.dataSource = self
            setViewControllers( [vcs[0]], direction: .forward, animated: false, completion: nil)
        }
        func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController?
        {
            let v = (viewController)
            let i = vcs.index(of: v)! - 1
            if i < 0 {
                return nil
            }
            return vcs[i]
        }
        func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController?
        {
            let v = (viewController)
            let i = vcs.index(of: v)! + 1
            if i > vcs.count - 1 {
                return nil
            }
            return vcs[i]
        }
        func presentationCount(for pageViewController: UIPageViewController) -> Int
        {
            return vcs.count
        }
        func presentationIndex(for pageViewController: UIPageViewController) -> Int
        {
            return 0
        }
    }
    @UIApplicationMain
    class AppDelegate: UIResponder, UIApplicationDelegate
    {
        var Window: UIWindow?
        func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
            self.Window = UIWindow(frame: UIScreen.main.bounds)
            self.window!.rootViewController = PageViewController()
            self.window?.makeKeyAndVisible()
            return true
        }
    }

前面的兩個類都是UIViewController的子類，每個初始化一個標簽，內容不同以示區別。類PageViewController是UIPageViewController的子類，實現了UIPageViewControllerDataSource並在裝入時設置數據源為自身。通過：

     setViewControllers( [vcs[0]], direction: .forward, animated: false, completion: nil)
     

設置UIPageViewController的當前的ViewController。這裡設置的是Page1的實例，因此App啟動後顯示的初始頁面就是Page1。

協議UIPageViewControllerDataSource的內容如下：

    public protocol UIPageViewControllerDataSource : NSObjectProtocol {
        public func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController?
        public func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController?
        optional public func presentationCount(for pageViewController: UIPageViewController) -> Int // The number of items reflected in the page indicator.
        optional public func presentationIndex(for pageViewController: UIPageViewController) -> Int // The selected item reflected in the page indicator.
    }

其中前兩個函數會有UIKit傳入當前視圖，希望App返回此視圖的前一個視圖或者是後一個視圖。後兩個函數分別返回總頁面數量和初始頁面對應的選擇項索引，這兩個函數是可選實現的，如果實現了，就會在頁面底部顯示頁面指示器。

以上就是對PageViewController的相關介紹，希望對您學習IOS有所幫助，感謝您關注本站!

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