ios - uipageviewcontroller 禁用向右滑动

Question

我有一个 uipageviewcontroller，里面有四个单独的 View Controller 。我想禁用第一个 View Controller 的右滑动操作并禁用第四个 View Controller 的左滑动操作。当应用程序启动时，我希望用户只能向左滑动而不能向右滑动，因为向右滑动会将用户带到第四个 View Controller ，而在第四个 View Controller 上向左滑动会将用户带到第一个 View Controller 。这是我的代码。

class TutorialPageViewController: UIPageViewController, UIPageViewControllerDataSource, UIPageViewControllerDelegate {
    weak var tutorialDelegate: TutorialPageViewControllerDelegate?

    lazy var VCArr: [UIViewController] = {
        return [self.VCInstance(name: "FirstVC"),
                self.VCInstance(name: "SecondVC"),
                self.VCInstance(name: "ThirdVC"),
                self.VCInstance(name: "FourthVC")]

    }()

    private func VCInstance(name: String) -> UIViewController {
        return UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: name)
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        let pageControl = UIPageControl.appearance()
        //Customizing
        pageControl.pageIndicatorTintColor = UIColor.lightGray
        pageControl.currentPageIndicatorTintColor = UIColor(red:0.23, green:0.73, blue:1.00, alpha:1.0)

        dataSource = self
        delegate = self
        self.dataSource = self
        self.delegate = self

        if let FirstVC = VCArr.first {
            setViewControllers([FirstVC], direction: .forward, animated: true, completion: nil)
            tutorialDelegate?.tutorialPageViewController(tutorialPageViewController: self, didUpdatePageCount: VCArr.count)

        }
    }

   override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()

        for view in self.view.subviews {
            if view is UIScrollView {
                view.frame = UIScreen.main.bounds
            } else if view is UIPageControl {
                view.backgroundColor = UIColor.clear
            }
        }
    }

    public func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
        guard let viewControllerIndex = VCArr.index(of: viewController) else {
            return nil
        }

        let previousIndex = viewControllerIndex - 1

        guard previousIndex >= 0 else {
            return VCArr.last
        }

        guard VCArr.count > previousIndex else {
            return nil
        }
        return VCArr[previousIndex]
    }

    public func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
        guard let viewControllerIndex = VCArr.index(of: viewController) else {
            return nil
        }

        let nextIndex = viewControllerIndex + 1

        guard nextIndex < VCArr.count else {
            return VCArr.first
        }

        guard VCArr.count > nextIndex else {
            return nil
        }
        return VCArr[nextIndex]
    }

    public func presentationCount(for pageViewController: UIPageViewController) -> Int {
        return VCArr.count
    }


    public func presentationIndex(for pageViewController: UIPageViewController) -> Int {
        guard let firstViewController = viewControllers?.first,
        let firstViewControllerIndex = VCArr.index(of: firstViewController) else {
             return 0
         }
         return firstViewControllerIndex
     }
}

extension TutorialPageViewController {

    func pageViewController(pageViewController: UIPageViewController,
                            didFinishAnimating finished: Bool,
                            previousViewControllers: [UIViewController],
                            transitionCompleted completed: Bool) {
        if let firstViewController = viewControllers?.first,
            let index = VCArr.index(of: firstViewController) {
            tutorialDelegate?.tutorialPageViewController(tutorialPageViewController: self, didUpdatePageIndex: index)
        }
    }

}

Answer 1

基本上你需要更改以下几行

guard previousIndex >= 0 else {
            return nil
        }


guard nextIndex < VCArr.count else {
            return nil
        }

----- 或 -----

将 viewControllerAfter 更改为

 public func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
            guard let viewControllerIndex = VCArr.index(of: viewController) else {
                return nil
            }

            let nextIndex = viewControllerIndex + 1

            guard nextIndex < VCArr.count else {
            return nil
        }

            guard VCArr.count > nextIndex else {
                return nil
            }

            return VCArr[nextIndex]
        }

将 ViewControllerBefore 更改为

public func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
        guard let viewControllerIndex = VCArr.index(of: viewController) else {
            return nil
        }

        let previousIndex = viewControllerIndex - 1

       guard previousIndex >= 0 else {
            return nil
        }
        guard VCArr.count > previousIndex else {
            return nil
        }
        return VCArr[previousIndex]
    }