Ios 在UIPageViewController中获取用户滑动方向

UIPageViewControllerDataSource

的

viewControllerBeforeViewController

和

viewcontrollerbeforviewcontroller

这两种方法不指示滑动方向

UIPageViewController

委托的方法

transitionCompleted

，对我们也没有多大帮助。它只是告诉你页面是否被完全刷过

那么，我应该使用什么方法来准确地检测用户方向（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)
        }

    }
}
}

---

无法确定用户是向前还是向后滑动

您需要使用以下两种方法提供前后视图：

pageViewController:ViewController预览控制器：

pageViewController:viewControllerAfterViewController:

---

您可以通过向ViewController添加属性来跟踪索引，然后可以比较页面索引。

您应该同时使用

WillTransitionOnViewController:

和

didFinishAnimating:

委托方法来确定转换是向前还是向后。在类的开头声明两个索引变量，例如

currentIndex

和

nextIndex

（两者都是

Int

）

在

willTransitionOnViewControllers

方法中，将

nextIndex

设置为挂起的视图控制器的

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
    }
}

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

    }
}

结束编辑

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
    }
}

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

    }
}

此时，您可以计算转换是向前还是向后：如果

nextIndex

>

currentIndex

，则向前；如果

nextIndex

<

currentIndex

则向后。然后在

didFinishAnimating

中，如果

completed

为true（因此它完成了到下一个视图控制器的转换），则将

currentIndex

设置为等于

nextIndex

，以便您可以在需要指示屏幕上当前页面的任何位置使用

currentIndex

：

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
    }
}

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），而不是当前代码中的

pageItemController

最后，需要注意的是：您引用的枚举（

UIPageViewControllerNavigationDirection

）仅在

setViewControllers（u，direction:）

方法中使用

---

结束编辑

假设您有一个ViewController的本地数组，您可以使用此

委托

方法：

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
    }
}

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

    }
}

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

语句应该不会失败，但以防万一……

对于我的情况，我能够通过使用

func pageViewController（pageViewController:UIPageViewController，didffinishanimating finished:Bool，previousViewControllers:[AnyObject]，transitionCompleted completed:Bool）来确定滑动方向

这里是如何。假设您已经有了一种方法来引用名为
currentIndex
的当前索引。在上面的方法中，您已经有了关于
previousViewControllers
的信息，因此可以获得名为
previousIndex
的上一个索引

基本上，以下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

    }
  }
}

func pageViewController（pageViewController:UIPageViewController，didFinishAnimating finished:Bool，PreviousViewController:[AnyObject]，transitionCompleted completed:Bool）{
如果完成{
如果以前的索引<当前索引{//向前
}
如果上一个索引>当前索引{//反向，则为else
}
}
}
首先在viewControllerForIndex方法中指定viewcontroller.view.tag=索引，以便每个viewcontroller.view都有一个指定值

具有一个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，请执行以下操作

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
    }

func pageViewController（pageViewController:UIPageViewController，didFinishAnimating finished:Bool，PreviousViewController:[UIViewController]，transitionCompleted completed:Bool）{
如果！完成{
return//动画未完成时返回
}
将pCont=bottomDataContainer？.ViewController？[0]设为？CustomVC//take
外流VC
如果currentIndex
非常感谢您准确回答我的问题。请您解释一下如何获取挂起的viewController的索引。您会说“…等于挂起的视图控制器的itemIndex”，但我对如何做到这一点没有任何线索。答案的其余部分很清楚，写得很好——再次感谢@我已经用一些示例代码更新了我的答案。我真是太感谢你了！我想补充一下。当您移动到下一个控制器并立即向相反方向刷回时，会出现这种情况。在这种情况下，“WillTransitionViewController”不会在最后一次刷卡时调用。因此您必须添加：如果（已完成）{…}否则{nextIndex=previousViewController.index}我该怎么做？“您可以通过向ViewController添加属性来跟踪索引，然后可以比较页面索引。”。谢谢@CeceXX视图控制器将具有一个名为pageIndex的属性，如本教程所示：