检测 UIPageViewController 的当前页面

Question

我想检测当前页面，以便在显示最后一页时修改按钮的标题，并且 re-modify 每次用户从最后一页滑回倒数第二页时。

现在这些是我的委托方法和我的 ViewController 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]
}

谁能帮我准确检测显示的最后一页？我尝试了一些方法，但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。

感谢大家。

Answer 1

在这里你可以使用%运算符

来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

Answer 2

尝试获取pageViewController.viewControllers

中的第一个视图控制器

    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：

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

Answer 3

试试这个委托方法。

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

我的解决方案是实现 UIPageViewControllerDelegate 的功能 pageViewController(_:didFinishAnimating:previousViewControllers:transitionCompleted:) 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，我在其中存储所有要显示的视图控制器，currentIndex 是属性以跟踪当前页面（又名视图控制器）的索引，以便在我的代码的其他部分使用它。

Answer 5

像这样设置 didFinishAnimating pageViewController 数据源函数。存储数据源的属性。在这种情况下，我将其命名为 orderedViewControllers。然后当你滑动时，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)
}

检测 UIPageViewController 的当前页面

Detect current page of UIPageViewController

ios

swift3

uipageviewcontroller