Disable UIPageViewController bounce

Question

Searched a lot for this one, but couldn\'t find a proper solution yet.

Is it possible to disable the bounce effect of a UIPageViewController and still

Answer 1

Edited answer of Dong Ma, where:

• added - respects layout direction (Hebrew for example)
• fixed - wrong counting currentIndex when swipes very quick

Info:

• Written in Swift 5.0
• Builded and tested in Xcode 10.2.1
• iOS 12.0

How to:

1. Let's assume we have a UIViewController where UIPageViewController is added as child VC.

class ViewController: UIViewController {
    var pageNavigationController: UIPageViewController! 

    private var lastPosition: CGFloat
    private var nextIndex: Int
    var currentIndex: Int     

    // rest of UI's setups  
}

2. Set ViewController as delegate of UIPageViewController:

extension ViewController: UIPageViewControllerDataSource {

    func pageViewController(_ pageViewController: UIPageViewController, willTransitionTo pendingViewControllers: [UIViewController]) {
        guard
            let currentVisibleViewController = pageViewController.viewControllers?.first,
            let nextIndex = pageViewControllers.firstIndex(of: currentVisibleViewController)
        else {
            return
        }

        self.nextIndex = nextIndex
    }

    func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
        if completed, let currentVisibleViewController = pageViewController.viewControllers?.first, let newIndex = pageViewControllers.firstIndex(of: currentVisibleViewController) {
            self.currentIndex = newIndex
        }

        self.nextIndex = self.currentIndex
    }
}

3. Set ViewController as datasource of UIPageController:

extension ViewController: UIPageViewControllerDataSource {

    func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
        // provide next VC
    }

    func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
        // provide prev VC
    }

    // IMPORTANT: that's the key why it works, don't forget to add it
    func presentationIndex(for pageViewController: UIPageViewController) -> Int {
        return currentIndex
    }
}

4. "Disable" bouncing by setting ViewController as delegate of UIPageViewController's UIScrollView:

// MARK: - UIScrollViewDelegate (disable bouncing for UIPageViewController)
extension BasePaginationVC: UIScrollViewDelegate {

    func attachScrollViewDelegate() {
        for subview in pageNavigationController.view.subviews {
            if let scrollView = subview as? UIScrollView {
                scrollView.delegate = self
                lastPosition = scrollView.contentOffset.x
                break
            }
        }
    }

    func scrollViewDidScroll(_ scrollView: UIScrollView) {
        switch UIView.userInterfaceLayoutDirection(for: view.semanticContentAttribute) {
        case .leftToRight:
            if nextIndex > currentIndex {
                if scrollView.contentOffset.x < (lastPosition - (0.9 * scrollView.bounds.size.width)) {
                    currentIndex = nextIndex
                }
            } else {
                if scrollView.contentOffset.x > (lastPosition + (0.9 * scrollView.bounds.size.width)) {
                    currentIndex = nextIndex
                }
            }

            if currentIndex == 0 && scrollView.contentOffset.x < scrollView.bounds.size.width {
                scrollView.contentOffset = CGPoint(x: scrollView.bounds.size.width, y: 0)
            } else if currentIndex == pageViewControllers.count - 1 && scrollView.contentOffset.x > scrollView.bounds.size.width {
                scrollView.contentOffset = CGPoint(x: scrollView.bounds.size.width, y: 0)
            }
        case .rightToLeft:
            if nextIndex > currentIndex {
                if scrollView.contentOffset.x > (lastPosition + (0.9 * scrollView.bounds.size.width)) {
                    currentIndex = nextIndex
                }
            } else {
                if scrollView.contentOffset.x < (lastPosition - (0.9 * scrollView.bounds.size.width)) {
                    currentIndex = nextIndex
                }
            }

            if currentIndex == pageViewControllers.count - 1 && scrollView.contentOffset.x < scrollView.bounds.size.width {
                scrollView.contentOffset = CGPoint(x: scrollView.bounds.size.width, y: 0)
            } else if currentIndex == 0 && scrollView.contentOffset.x > scrollView.bounds.size.width {
                scrollView.contentOffset = CGPoint(x: scrollView.bounds.size.width, y: 0)
            }
        @unknown default:
            fatalError("unknown default")
        }

        lastPosition = scrollView.contentOffset.x
    }

    func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer) {
        switch UIView.userInterfaceLayoutDirection(for: view.semanticContentAttribute) {
        case .leftToRight:
            if currentIndex == 0 && scrollView.contentOffset.x <= scrollView.bounds.size.width {
                targetContentOffset.pointee = CGPoint(x: scrollView.bounds.size.width, y: 0)
            } else if currentIndex == pageViewControllers.count - 1 && scrollView.contentOffset.x >= scrollView.bounds.size.width {
                targetContentOffset.pointee = CGPoint(x: scrollView.bounds.size.width, y: 0)
            }
        case .rightToLeft:
            if currentIndex == pageViewControllers.count - 1 && scrollView.contentOffset.x <= scrollView.bounds.size.width {
                targetContentOffset.pointee = CGPoint(x: scrollView.bounds.size.width, y: 0)
            } else if currentIndex == 0 && scrollView.contentOffset.x >= scrollView.bounds.size.width {
                targetContentOffset.pointee = CGPoint(x: scrollView.bounds.size.width, y: 0)
            }
        @unknown default:
            fatalError("unknown default")
        }
    }
}