如何使用 UIPageViewController 在第一个和最后一个索引处停止 UIScrollView 的反弹？

Question

我有一个 UIViewController，我通过编程方式添加了 UIPageViewController。如果我们处于 0 索引或最后一个索引，如何停止反弹（滚动）UIViewController？我的意思是弹跳。

您可以查看此链接：How to create PageView with UITabBar or Segment Control using swift?

这是我的代码：

import UIKit

class ViewController: UIViewController {

fileprivate var pageViewController:UIPageViewController!
@IBOutlet weak var paginationView:UIView!
@IBOutlet var btnYourGroup: UIButton!
@IBOutlet var btnSharedBy: UIButton!
@IBOutlet var sliderViewLeadingConst: NSLayoutConstraint!

fileprivate var selectedIndex : Int? {
    didSet {
        var leading:CGFloat = 0
        if selectedIndex == 0 {
            leading = 0
        }
        else {
            leading = self.view.frame.size.width/2
        }

        self.sliderViewLeadingConst.constant = leading

        UIView.animate(withDuration: 0.2, animations: {

            self.view.layoutIfNeeded()
        })
    }
}

override func viewDidLoad() {
    super.viewDidLoad()

    //SetUp Pagination
    setupPagination()

    for view in self.pageViewController.view.subviews {
        if let scrollView = view as? UIScrollView {
            scrollView.delegate = self
            break
        }
    }

    //btnSharedBy.titleColor(for: UIControlState)
    btnSharedBy.setTitleColor(UIColor.lightGray, for: UIControlState())
}

private func setupPagination() {

    let startVC = self.viewControllerAtIndex(index: 0)
    let vc = [startVC]
    self.pageViewController = UIPageViewController(transitionStyle: .scroll, navigationOrientation: .horizontal, options: nil)
    self.pageViewController.setViewControllers(vc, direction: .reverse, animated: true, completion: nil)
    self.pageViewController.dataSource = self
    self.pageViewController.delegate = self
    self.pageViewController.view.frame.size = self.paginationView.frame.size
    self.paginationView.addSubview(self.pageViewController.view)
}

@IBAction func mainCateogryTapped(sender:UIButton) {
    loadNextController(index:sender.tag)
}

fileprivate func viewControllerAtIndex(index:Int) -> PageContentViewController {

    let feedsVC = self.storyboard?.instantiateViewController(withIdentifier: "PageContentViewController") as! PageContentViewController
    feedsVC.pageIndex = index
    return feedsVC
}

fileprivate func loadNextController(index:Int) {

    if selectedIndex == index {
        return
    }

    let nextViewController = viewControllerAtIndex(index:index)
    selectedIndex = index

    if index == 0 {
        btnSharedBy.setTitleColor(UIColor.lightGray, for: UIControlState())
        btnYourGroup.setTitleColor(UIColor.white, for: UIControlState())
        self.pageViewController?.setViewControllers([nextViewController], direction: UIPageViewControllerNavigationDirection.reverse, animated: true, completion: nil)
    } else if index == 1 {
        btnSharedBy.setTitleColor(UIColor.white, for: UIControlState())
        btnYourGroup.setTitleColor(UIColor.lightGray, for: UIControlState())
        self.pageViewController?.setViewControllers([nextViewController], direction: UIPageViewControllerNavigationDirection.forward, animated: true, completion: nil)
    }

    else {

    }
  }
}
extension ViewController: UIPageViewControllerDataSource {

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

    var index = (viewController as! PageContentViewController).pageIndex

    if index == 0 {
        return nil
    }
    index = index - 1
    return viewControllerAtIndex(index:index)

}

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

    var index = (viewController as! PageContentViewController).pageIndex

    index = index + 1
    if index == 2 {
        //self.pageViewController.
        return nil
    }
    return viewControllerAtIndex(index:index)
}

func pageViewController(_ pageViewController: UIPageViewController, willTransitionTo pendingViewControllers: [UIViewController]) {

    let vc : PageContentViewController = pendingViewControllers[0] as! PageContentViewController
    selectedIndex = vc.pageIndex
  }
}

extension ViewController : UIPageViewControllerDelegate {

func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
    if completed {
        let vc = previousViewControllers.first as! PageContentViewController

        if 0 == vc.pageIndex {
            selectedIndex = 1
            btnSharedBy.setTitleColor(UIColor.white, for: UIControlState())
            btnYourGroup.setTitleColor(UIColor.lightGray, for: UIControlState())

        }

        else {
            btnYourGroup.setTitleColor(UIColor.white, for: UIControlState())
            btnSharedBy.setTitleColor(UIColor.lightGray, for: UIControlState())
            selectedIndex = 0
        }
    }

    else if !completed {
        let pageContentView = previousViewControllers[0] as! PageContentViewController;
        self.selectedIndex = pageContentView.pageIndex
    }
  }
}

//ScrollView Delegate
extension ViewController : UIScrollViewDelegate {

func scrollViewDidScroll(_ scrollView: UIScrollView) {
    let point = scrollView.contentOffset
    var percentComplete: CGFloat
    percentComplete = fabs(point.x - view.frame.size.width)/view.frame.size.width
    //NSLog("percentComplete: %f", percentComplete)

        if(0.8 > percentComplete)
        {
            //selectedIndex = 1
            scrollView.bounces = false
        }

        else
        {
            scrollView.bounces = true

        }
    }
}

如何在第一个和最后一个索引处也使用按钮指示器停止弹跳问题？

Answer 1

您也许可以遍历页面视图控制器的子视图，寻找它的滚动视图，并将反弹设置为 false。然而，这是一个脆弱的解决方案，并且不明智。 （弄乱视图控制器的视图通常是个坏主意，尤其是在没有公共接口可以找到它们的情况下。）

下面的线程具有遍历页面视图控制器的子视图并找到滚动视图的代码。修改该代码以将 bounces 属性设置为 false 会很容易：

Progress of UIPageViewController