PageViewController current page index in Swift

Question

I want to get current index of a pageViewController, I don\'t know how I get the visible pages index.

func pageViewController(pageViewController: UIPageViewContr         


        

Answer 1

Just check apple's docs (https://developer.apple.com/tutorials/swiftui/interfacing-with-uikit) -> Section 3 -> Step 5

You can get the current index like this

func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
            if completed,
                let visibleViewController = pageViewController.viewControllers?.first,
                let index = parent.controllers.firstIndex(of: visibleViewController)
            {
                parent.currentPage = index
            }
        }

or if you are keeping viewControllers in an array you can do this

func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
        if completed,
            let visibleViewController = pageViewController.viewControllers?.first,
            let index = orderedViewControllers.firstIndex(of: visibleViewController)
        {
            statisticsPageDelegate?.statisticsPageViewController(statisticsPageViewController: self, didUpdatePageIndex: index)
        }
    }

This is the full code

class StatisticsPageViewController: UIPageViewController,UIPageViewControllerDataSource, UIPageViewControllerDelegate {

    var currentIndex: Int?
    var statisticsPageDelegate: StatisticsPageViewControllerDelegate?
    private var pendingIndex: Int?

    required init?(coder aDecoder: NSCoder) {
        super.init(transitionStyle: .scroll, navigationOrientation: .horizontal, options: nil)
    }
    override func viewDidLoad() {
        super.viewDidLoad()
        dataSource = self
        delegate = self

        if let firstViewController = orderedViewControllers.first {
            setViewControllers([firstViewController],
                               direction: .forward,
                               animated: true,
                               completion: nil)
        }

        statisticsPageDelegate?.statisticsPageViewController(
            statisticsPageViewController: self,
            didUpdatePageCount: orderedViewControllers.count
        )
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

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

        let previousIndex = viewControllerIndex - 1

        guard previousIndex >= 0 else {
            return nil
        }

        guard orderedViewControllers.count > previousIndex else {
            return nil
        }

        return orderedViewControllers[previousIndex]
    }

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

        let nextIndex = viewControllerIndex + 1
        let orderedViewControllersCount = orderedViewControllers.count

        guard orderedViewControllersCount != nextIndex else {
            return nil
        }

        guard orderedViewControllersCount > nextIndex else {
            return nil
        }

        return orderedViewControllers[nextIndex]
    }

    func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
        if completed,
            let visibleViewController = pageViewController.viewControllers?.first,
            let index = orderedViewControllers.firstIndex(of: visibleViewController)
        {
            statisticsPageDelegate?.statisticsPageViewController(statisticsPageViewController: self, didUpdatePageIndex: index)
        }
    }

    private(set) lazy var orderedViewControllers: [UIViewController] = {
        return [self.newStatisticsViewController(identifier: Identifiers.PROGRAM_VIEW_CONTROLLER),
        self.newStatisticsViewController(identifier: Identifiers.LOGIN_VIEW_CONTROLLER)]
    }()

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

protocol StatisticsPageViewControllerDelegate: class {
    func statisticsPageViewController(statisticsPageViewController:
        StatisticsPageViewController, didUpdatePageCount count: Int)
    func statisticsPageViewController(statisticsPageViewController:
        StatisticsPageViewController, didUpdatePageIndex index: Int)
}