以編程方式推進UIPageViewController - Swift

Question

這是我第一次嘗試iOS應用程序，並且我沒有使用swift的經驗，並且很多代碼都是從Web中借用並編輯的。

我正在嘗試創建一組幻燈片。我從主着陸頁轉到另一個運行幻燈片的View Controller，TestVC。登陸頁面和幻燈片工作。我可以來回滑動。我現在正在嘗試添加計時器，以便幻燈片每5秒鐘左右自動前進一次。

我認爲，這需要運行的代碼是：

pageViewController.setViewControllers(varPageVC, direction: UIPageViewControllerNavigationDirection.forward, animated: true, completion: nil) 

我得到一個錯誤：

test.swift:31:9: Ambiguous reference to member 'pageViewController(_:viewControllerBefore:)'. 

我不知道如何解釋這個錯誤，繼續前進。該錯誤在test.swift中觸發，其中計時器調用嘗試前進幻燈片的函數。建議表示讚賞。如果我做錯了，請指出我的方向。

登陸頁面有一個按鈕，打開一個ViewController testVC。我有2個文件，test.swift和alphabetItemController.swift。故事板除了登陸頁面ViewController之外，還有稱作字母PVC的，稱爲字母VC的ViewController和稱爲TestVC的ViewController。

這裏是alphabetItemController.swift代碼...

import UIKit 

class alphabetItemController: UIViewController { 

    @IBOutlet weak var contentImageView2: UIImageView! 
    @IBOutlet weak var contentWordPn: UILabel! 

    var itemIndex: Int = 0 
    var imageName: String = "" 
    var wordPN: String = "" 

    var tTime: Timer! 

    override func viewDidLoad() { 
     super.viewDidLoad() 

     contentImageView2!.image = UIImage(named: imageName) 
     contentWordPn!.text = wordPN 

    } 

} 

這裏是test.swift代碼...

import Foundation 
import UIKit 

class testItemController: UIViewController, UIPageViewControllerDataSource { 

    var tTime: Timer! 

    override func viewDidLoad() { 
     super.viewDidLoad() 

     createPageViewController() 
     setupPageControl() 

     tTime = Timer.scheduledTimer(timeInterval: 5, target: self, selector: #selector(changeSlide), userInfo: nil, repeats: true) 
     //tTime = Timer.scheduledTimer(timeInterval: 5, target: self, selector: #selector(goToNextPage), userInfo: nil, repeats: true) 

    } 


    func changeSlide() { 
     pageViewController.setViewControllers(varPageVC, direction: UIPageViewControllerNavigationDirection.forward, animated: true, completion: nil) 
    } 


    // MARK: - Variables 
    private var varPageVC: UIPageViewController? 


    private let contentTextWordPN = ["A", "B", "C", "D", "E"] 
    private let contentCount = 5 //TODO ADJUST THIS FOR EACH COLLECTION 


    private func createPageViewController() { 

     let pageController = self.storyboard!.instantiateViewController(withIdentifier: "alphabetPVC") as! UIPageViewController 

     pageController.dataSource = self 

     if contentCount > 0 { 
      let firstController = getItemController(itemIndex: 0)! 
      let startingViewControllers = [firstController] 
      pageController.setViewControllers(startingViewControllers, direction: UIPageViewControllerNavigationDirection.forward, animated: false, completion: nil) 
     } 

     varPageVC = pageController 
     addChildViewController(varPageVC!) 
     self.view.addSubview(varPageVC!.view) 
     varPageVC!.didMove(toParentViewController: self) 
    } 

    private func setupPageControl() { 
     let appearance = UIPageControl.appearance() 
     appearance.pageIndicatorTintColor = UIColor.gray 
     appearance.currentPageIndicatorTintColor = UIColor.white 
     appearance.backgroundColor = UIColor.darkGray 
    } 

    func pageViewController(_ varPageVC: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? { 

     let itemController = viewController as! alphabetItemController 

     if itemController.itemIndex > 0 { 
      return getItemController(itemIndex: itemController.itemIndex-1) 
     } 

     return nil 
    } 

    func pageViewController(_ varPageVC: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? { 

     let itemController = viewController as! alphabetItemController 

     if itemController.itemIndex+1 < contentCount { 
      return getItemController(itemIndex: itemController.itemIndex+1) 
     } 

     return nil 
    } 

    private func getItemController(itemIndex: Int) -> alphabetItemController? { 

     if itemIndex < contentCount { 
      let pageItemController = self.storyboard!.instantiateViewController(withIdentifier: "alphabetVC") as! alphabetItemController 

      pageItemController.itemIndex = itemIndex 
      pageItemController.imageName = "alphabet_" + String(format: "%02d", (itemIndex + 1)) //alphabet_01 

      pageItemController.wordPN = contentTextWordPN[itemIndex] 


      return pageItemController 
     } 

     return nil 
    } 

    func presentationCountForPageViewController(varPageVC: UIPageViewController) -> Int { 
     return contentCount 
    } 

    func presentationIndexForPageViewController(varPageVC: UIPageViewController) -> Int { 
     return 0 
    } 

    func currentControllerIndex() -> Int { 

     let pageItemController = self.currentController() 

     if let controller = pageItemController as? alphabetItemController { 
      return controller.itemIndex 
     } 

     return -1 
    } 

    func currentController() -> UIViewController? { 

     if (self.varPageVC?.viewControllers?.count)! > 0 { 
      return self.varPageVC?.viewControllers![0] 
     } 

     return nil 
    } 

} 

extension UIPageViewController { 

    func goToNextPage(animated: Bool = true) { 
     guard let currentViewController = self.viewControllers?.first else { return } 
     guard let nextViewController = dataSource?.pageViewController(self, viewControllerAfter: currentViewController) else { return } 
     setViewControllers([nextViewController], direction: .forward, animated: animated, completion: nil) 
    } 

    func goToPreviousPage(animated: Bool = true) { 
     guard let currentViewController = self.viewControllers?.first else { return } 
     guard let previousViewController = dataSource?.pageViewController(self, viewControllerBefore: currentViewController) else { return } 
     setViewControllers([previousViewController], direction: .reverse, animated: animated, completion: nil) 
    } 

} 

甚至還有一個擴展UIPageViewController，但我不知道如何調用goToNextPage函數。

Answer 1

我最終改變了changeSlide()函數......我已經在擴展中使用了下一個幻燈片函數，只有調用它的語法才避開我......我在SO上找到了一些例子，並將它們用作參考：

func changeSlide() { 
    varPageVC?.goToNextPage() 
}