在 UIPageViewController 中获取用户滑动方向
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【中文标题】在 UIPageViewController 中获取用户滑动方向【英文标题】：Get user swiping direction in UIPageViewController 【发布时间】：2015-01-13 21:36:56 【问题描述】：UIPageViewControllerDataSource 的 viewControllerBeforeViewController 和 viewControllerAfterViewController 这两个方法不知道滑动的方向。
UIPageViewController 委托的方法transitionCompleted 也对我们没有多大帮助。它只是告诉页面是否被完全刷过。
那么我应该使用什么方法来准确检测用户方向（左或右）？
这两个属性可能会有所帮助：
let directionForward = UIPageViewControllerNavigationDirection.Forward
let directionReverse = UIPageViewControllerNavigationDirection.Reverse
我的代码如下所示：
import UIKit
class ProView: UIViewController, UIPageViewControllerDataSource, UIPageViewControllerDelegate
var pageViewController: UIPageViewController?
let characterImages = ["character1", "character2", "character1", "character2", "character1", "character2", "character1", "character2"]
override func viewDidLoad()
super.viewDidLoad()
createPageViewController()
setupPageControl()
character = 1
override func didReceiveMemoryWarning()
super.didReceiveMemoryWarning()
// Forward, check if this IS NOT the last controller
func pageViewController(pageViewController: UIPageViewController,
viewControllerAfterViewController ProView: UIViewController) -> UIViewController?
let itemController = ProView as PageItemController
// Check if there is another view
if itemController.itemIndex+1 < characterImages.count
return getItemController(itemController.itemIndex+1)
return nil
// Check if this IS NOT the first controller
func pageViewController(pageViewController: UIPageViewController,
viewControllerBeforeViewController ProView: UIViewController) -> UIViewController?
let itemController = ProView as PageItemController
if itemController.itemIndex < 0
return getItemController(itemController.itemIndex-1)
return nil
private func getItemController(itemIndex: Int) -> PageItemController?
if itemIndex < characterImages.count
let pageItemController = self.storyboard!.instantiateViewControllerWithIdentifier("ItemController") as PageItemController
pageItemController.itemIndex = itemIndex
pageItemController.imageName = characterImages[itemIndex]
return pageItemController
return nil
func createPageViewController()
let pageController = self.storyboard!.instantiateViewControllerWithIdentifier("PageController") as UIPageViewController
pageController.dataSource = self
pageController.delegate = self
if characterImages.count > 0
let firstController = getItemController(0)!
let startingViewControllers: NSArray = [firstController]
pageController.setViewControllers(startingViewControllers, direction: UIPageViewControllerNavigationDirection.Forward, animated: false, completion: nil)
pageViewController = pageController
addChildViewController(pageViewController!)
self.view.addSubview(pageViewController!.view)
pageViewController?.didMoveToParentViewController(self)
func setupPageControl()
let appearance = UIPageControl.appearance()
appearance.pageIndicatorTintColor = UIColor.grayColor()
appearance.currentPageIndicatorTintColor = UIColor.whiteColor()
func presentationCountForPageViewController(pageViewController: UIPageViewController) -> Int
return characterImages.count
func presentationIndexForPageViewController(pageViewController: UIPageViewController) -> Int
// BETA
func pageViewController(PageItemController: UIPageViewController,
didFinishAnimating finished: Bool,
previousViewControllers pageViewController: [AnyObject],
transitionCompleted completed: Bool)
if (!completed)
// You do nothing because whatever page you thought
// the book was on before the gesture started is still the correct page
return;
// This is where you would know the page number changed and handle it appropriately
character = workaround
class PageItemController: UIViewController
@IBOutlet weak var imageCharacterChoose: UIImageView!
var itemIndex: Int = 0
var imageName: String = ""
didSet
if let imageView = imageCharacterChoose imageCharacterChoose.image = UIImage(named: imageName)
根据pbasdf所说，
var currentIndex: Int = 0
var nextIndex: Int = 0
func pageViewController(PageItemController: UIPageViewController,
willTransitionToViewControllers pageViewController: [AnyObject])
// pageViewController is the pending View Controller
nextIndex = currentIndex
// pageViewController...... how do I get its index?
【问题讨论】：
【参考方案1】：您应该同时使用willTransitionToViewControllers: 和didFinishAnimating: 委托方法来确定过渡是向前还是向后。在你的课程开始时声明几个索引变量，比如currentIndex 和nextIndex（都是Int）。
在willTransitionToViewControllers方法中，设置nextIndex等于待处理视图控制器的itemIndex：
编辑
func pageViewController(pageViewController: UIPageViewController, willTransitionToViewControllers pendingViewControllers: [AnyObject])
// the page view controller is about to transition to a new page, so take note
// of the index of the page it will display. (We can't update our currentIndex
// yet, because the transition might not be completed - we will check in didFinishAnimating:)
if let itemController = pendingViewControllers[0] as? PageItemController
nextIndex = itemController.itemIndex
结束编辑
此时您可以计算出是向前还是向后过渡：如果nextIndex > currentIndex，则向前；如果 nextIndex currentIndex 则向后。然后在didFinishAnimating 中，如果completed 为真（所以它完成了到下一个视图控制器的转换），将currentIndex 设置为等于nextIndex，这样您就可以在需要指示当前哪个页面的任何地方使用currentIndex在屏幕上：
编辑
func pageViewController(pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [AnyObject], transitionCompleted completed: Bool)
if (completed)
// the page view controller has successfully transitioned to the next view
// controller, so we can update our currentIndex to the value we obtained
// in the willTransitionToViewControllers method:
currentIndex = nextIndex
请注意，这些方法的第一个参数是 pageViewController（UIPageViewController 的实例），而不是您当前代码中的 pageItemController。
最后，请注意：您引用的枚举 (UIPageViewControllerNavigationDirection) 仅在 setViewControllers(_, direction:) 方法中使用。
结束编辑
【讨论】：
非常感谢您准确回答我的问题。请您解释一下如何获取待处理视图控制器的索引。你说“......等于待处理视图控制器的 itemIndex”，但我知道如何做到这一点。其余的答案很清楚而且很好 - 再次感谢！ @CeceXX 我已经用一些示例代码更新了我的答案。 非常感谢！ 我想在这里添加。有时您移动到下一个控制器并立即向相反方向滑动。在这种情况下，不会在最后一次滑动时调用“willTransitionToViewControllers”。所以你必须添加： if (completed) ... else nextIndex = previousViewController.index 【参考方案2】：就我而言，我只能使用func pageViewController(pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [AnyObject], transitionCompleted completed: Bool) 来确定滑动方向。
这里是如何。假设您已经有一种方法可以引用名为currentIndex 的当前索引。在上面的方法中，你已经有了previousViewControllers的信息，这样你就可以得到之前名为previousIndex的索引。
基本上，这是委托方法内部的实现：
func pageViewController(pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [AnyObject], transitionCompleted completed: Bool)
if completed
if previousIndex < currentIndex // forward
else if previousIndex > currentIndex // reverse
【讨论】：
【参考方案3】：假设你有一个 ViewControllers 的本地数组，你可以使用这个delegate 方法：
func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool)
guard let current = self.viewControllers?.first else
// TODO handle error
return
guard let index = self.pages.firstIndex(of: current) else
// TODO handle error
return
self.currentIndex = index
guard 语句不应失败，但以防万一......
【讨论】：
【参考方案4】：首先在您的 viewControllerForIndex 方法中分配 viewcontroller.view.tag = index 以便每个 viewcontroller.view 都有一个分配的值
有一个 currentIndex 属性，该属性最初分配给您在 pageviewcontroller 中实例化的 viewcontroller 的索引
现在在 didFinishAnimating 中执行以下操作
func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool)
if !completed
return // return if animation is not completed
let pCont = bottomDataContainer?.viewControllers?[0] as? CustomVC //take
out current VC
if currentIndex < pCont?.view.tag ?? 0
topNavView.goToNextDate()
else
topNavView.goToPrevDate()
selectedIndex = pCont?.view.tag ?? 0
【讨论】：
【参考方案5】：你可以通过实现UIScrollViewDelegate：
var lastScrollDirection: UIPageViewController.NavigationDirection?
func scrollViewWillBeginDragging(_ scrollView: UIScrollView)
let translation = scrollView.panGestureRecognizer.translation(in: scrollView.superview)
self.lastScrollDirection = translation.x < 0 ? .forward : .reverse
分配委托可能比较棘手。这是我在一个项目中使用的：
func assignScrollDelegate(rootView: UIView)
for view in rootView.subviews
if let scrollView = view as? UIScrollView
scrollView.delegate = self
else
assignScrollDelegate(rootView: view)
当您有对UIPageViewController 的引用时调用它。例如，当您的控制器加载时：
override func viewDidLoad()
self.assignScrollDelegate(rootView: self.pageController.view)
【讨论】：
这很有帮助，但您可能希望使用scrollViewDidEndDragging 而不是 scrollViewWillBeginDragging 来更新您的模型【参考方案6】：
无法确定用户是向前还是向后滑动。
你需要使用这两种方法来提供前后的视图：
pageViewController:viewControllerBeforeViewController:
pageViewController:viewControllerAfterViewController:
您可以通过向 viewControllers 添加属性来跟踪索引，然后您可以比较 pageIndexes。
【讨论】：
我该怎么做呢？ “您可以通过向 viewControllers 添加属性来跟踪索引，然后您可以比较 pageIndexes。”。谢谢！ @CeceXX 视图控制器将有一个名为 pageIndex 的属性，如本教程：makemegeek.com/uipageviewcontroller-example-ios以上是关于在 UIPageViewController 中获取用户滑动方向的主要内容，如果未能解决你的问题，请参考以下文章
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