Swift - UIPageViewController总是重复第二个ViewController

Question

设置:我正在尝试创建一个带有嵌入式UIPageViewController的ViewController,它有4个页面,每个页面都是自己的ViewController.

问题:滚动时总是重复第二个视图.例如,使用View1,View2,View3,View4滚动显示View1,View2,View2,View3,View4然后向后滚动具有此顺序View4,View3,View3,View2,View1即使页面控件准确.

我在网上看了很多教程,包括这里和这里的答案.

这是我的页面视图控制器类:

import UIKit

class HostGamePageViewController: ROLViewController, UIPageViewControllerDelegate, UIPageViewControllerDataSource {

  // Constants
  let ViewControllers: NSArray = ["HostGameTest1", "HostGameTest2", "HostGameTest3", "HostGameTest4"]

  // Properties
  var pageViewController: UIPageViewController!
  var currentViewController: String!

  // UI
  @IBOutlet var pageControl: UIPageControl!

  override func viewDidLoad() {
    super.viewDidLoad()

    pageViewController = storyboard?.instantiateViewControllerWithIdentifier("HGPageViewController") as? UIPageViewController
    pageViewController.delegate = self
    pageViewController.dataSource = self

    let startingViewController = viewControllerAtIndex(0)!
    pageViewController.setViewControllers([startingViewController], direction: UIPageViewControllerNavigationDirection.Forward, animated: false, completion: {done in })

    addChildViewController(pageViewController)
    view.addSubview(pageViewController.view)
    pageViewController.view.frame = view.bounds
    pageViewController.didMoveToParentViewController(self)
    view.gestureRecognizers = pageViewController.gestureRecognizers

    // Setup page controls
    pageControl.numberOfPages = ViewControllers.count
    view.bringSubviewToFront(pageControl)
  }

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

  // Get the index of the current page view
  func indexOfViewController() -> Int {
    if currentViewController != nil {
      return ViewControllers.indexOfObject(currentViewController)
    }

    return NSNotFound
  }

  // Get the view controller of the given index
  func viewControllerAtIndex(index: Int) -> UIViewController? {
    if ViewControllers.count == 0 || index >= ViewControllers.count {
      return nil
    }

    pageControl.currentPage = index
    currentViewController = ViewControllers[index] as String

    return storyboard?.instantiateViewControllerWithIdentifier(currentViewController) as? ROLViewController
  }

  // Handle clicks on the page control
  @IBAction func pageControlClick(sender: UIPageControl) {
    var direction: UIPageViewControllerNavigationDirection

    if sender.currentPage < indexOfViewController() {
      direction = UIPageViewControllerNavigationDirection.Forward
    } else {
      direction = UIPageViewControllerNavigationDirection.Reverse
    }

    if let viewController = viewControllerAtIndex(sender.currentPage) {
      pageViewController.setViewControllers([viewController], direction: direction, animated: false, completion: nil)
    }
  }

  func pageViewController(pageViewController: UIPageViewController, viewControllerBeforeViewController viewController: UIViewController) -> UIViewController? {
    var index = indexOfViewController()

    if index == 0 || index == NSNotFound {
      return nil
    }

    index--
    return viewControllerAtIndex(index)
  }

  func pageViewController(pageViewController: UIPageViewController, viewControllerAfterViewController viewController: UIViewController) -> UIViewController? {
    var index = indexOfViewController()

    if index == NSNotFound {
      return nil
    }

    index++
    if index == ViewControllers.count {
      return nil
    }

    return viewControllerAtIndex(index)
  }

}

这里是我的故事板截图的链接:http: //f.cl.ly/items/0V3W133Q34170q39393Q/Image%202014-09-11%20at%2011.49.44%20AM.png

我是否错误地设置了dateSource？我在某处看到UIPageViewController通过将动画变为false来做一些缓存,这是假定的修复,对我没有做任何事情.任何帮助将非常感激.谢谢!

Answer 1

我有一个非常类似的问题(不使用swift,在obj-c中,有3个视图控制器,中间的一个重复一次:"0,1,1,2").原来它是关于页面视图控制器数据源方法...

- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController *)viewController;
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController;

我还没有真正深入研究swift(也没有兴趣这样做),但伪读你的代码让我想到你限制了" 之前 "和" 之后 "关键方法的限制(迅捷)将变量包含在用作UIPageViewControllerDataSource的控制器中,这正是我改变并修复了问题.

我没有最好的英语,但我希望你能理解最后的陈述.我使用的修复程序基于本教程.在我的情况下,视图控制器我在所有3个案例中使用了"UINavigationViewControllers",所以我创建了一个具有属性的"NavigationWrapperViewController":

@property(assign, nonatomic) NSUInteger index;

然后,当检查关键数据源方法中的边界限制时(仅显示一个,对另一个使用相同的技术):

- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController *)viewController {
   NSUInteger indice = ((NavigationWrapperViewController*)viewController).index;
   if ((indice == 0) || (indice == NSNotFound)) {
       return nil;
   }    
   return [self viewControllerAtIndex:(--indice)];
}

在viewControllerAtIndex中实例化视图控制器时,不要忘记在返回它们之前正确设置该属性:

NavigationWrapperViewController *wrapperViewController = [self.storyboard instantiateViewControllerWithIdentifier:self.ViewControllers[index]];
wrapperViewController.index = index;

return wrapperViewController;

微妙的区别在于显示的视图控制器的索引由当前视图控制器存储(使用一个简单的包装器,该类完全是为了这个目的,它只是在他的.h文件中有一个属性实现)而不是UIPageViewControllerDataSource负责任的课.

这解决了我的问题,也许是某种线程相关的问题影响了当前视图控制器索引被提取并导致整个 - 重复视图控制器 - 问题.

希望如果您愿意尝试它会有所帮助!