Question

我想检测当前页面，以便在最后一页显示时修改按钮的标题，并在每次用户从最后一页向最后一页向后滑动时重新修改。

现在这些是我的委托方法和我的ViewControllers数组：

lazy var VCArr: [UIViewController] = {
    let firstVC = self.storyboard!.instantiateViewController(withIdentifier: "FirstTutorialPage")
    let secondVC = self.storyboard!.instantiateViewController(withIdentifier: "SecondTutorialPage")
    let thirdVC = self.storyboard!.instantiateViewController(withIdentifier: "ThirdTutorialPage")
    let fourthVC = self.storyboard!.instantiateViewController(withIdentifier: "FourthTutorialPage")
    return [firstVC, secondVC, thirdVC, fourthVC]
}()

委托方法

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

    guard let viewControllerIndex = self.VCArr.index(of: viewController) else {
        return nil
    }

    let previousIndex = viewControllerIndex - 1

    guard previousIndex >= 0 else {
        return nil
    }

    guard self.VCArr.count > previousIndex else {
        return nil
    }

    return self.VCArr[previousIndex]
}

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

    let nextIndex = viewControllerIndex + 1

    guard nextIndex < self.VCArr.count else {
        return nil
    }

    guard self.VCArr.count > nextIndex else {
        return nil
    }

    return self.VCArr[nextIndex]
}

有人可以帮助我准确地检测显示的最后一页吗？我尝试了一些方法，但是他们每个人都向我展示了错误的索引。这些方法在显示倒数第二页时检测到最后一个索引。

感谢所有人。

Answer 1

我的解决方案包括实现pageViewController(_:didFinishAnimating:previousViewControllers:transitionCompleted:)的函数UIPageViewControllerDelegate并执行以下操作：

if completed {
    if let currentViewController = pageViewController.viewControllers?.first,
    let index = pages.index(of: currentViewController) {
        currentIndex = index
    }
}

其中pages是我的页面视图控制器的属性，我存储了要呈现的所有视图控制器，currentIndex是一个属性，用于跟踪当前页面的索引（也称为视图控制器））以便在我的代码的其他部分使用它。

Answer 2

尝试在 pageViewController.viewControllers中获取第一个视图控制器

    if let vc = pageViewController.viewControllers?[0] {
        ... vc is current controller...
    }

如果要处理页面更改，请在委托方法中执行此操作：

func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
    if let vc = pageViewController.viewControllers?[0] {
        ... vc is current controller...
    }
}

Answer 3

尝试此委托方法。

var currentIndex = 0

func pageViewController(_ pageViewController: UIPageViewController, willTransitionTo pendingViewControllers: [UIViewController]) {
    guard let nextViewController = pendingViewControllers[0] as? ViewController else { return }
    self.currentIndex = nextViewController.index
}

Answer 4

像这样设置didFinishAnimating pageViewController DataSource函数。存储数据源的属性。在这种情况下，我将其命名为orderedViewControllers。然后，在滑动时，当前索引将被打印到控制台。

func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
    let pageContentViewController = pageViewController.viewControllers![0]
    let index = orderedViewControllers.index(of: pageContentViewController)!
    print(index)
}

Answer 5

您可以使用%运算符

计算上一项和下一项的索引

let nextIndex = (viewControllerIndex + 1) % VCArr.count
let previousIndex = (VCArr.count + viewControllerIndex - 1) % VCArr.count

检测UIPageViewController

5 个答案: