ios - 错误：页面控制跳转两次单页交换

Question

使用以下代码，页面控件在单页交换期间跳转了两次而不是一次。我需要添加UIPageViewControlleras 子视图，如下所示，我怎样才能使 pagecontrol 正确？谢谢！

import UIKit

class ViewController: UIViewController, UIPageViewControllerDataSource, UIPageViewControllerDelegate{

    var pageViewController: UIPageViewController!
    let pagesArray = ["Page1ViewController", "Page2ViewController","Page3ViewController"]
    let pageControl : UIPageControl = UIPageControl(frame: CGRectMake(100, 600, 200, 20))


    func viewControllerAtIndex(index: Int) -> UIViewController? {
        let vc = storyboard?.instantiateViewControllerWithIdentifier (pagesArray[index])
        return vc
    }

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

            if var index = pagesArray.indexOf(viewController.restorationIdentifier!){
                if index > 0 {
                    index--
                    self.pageControl.currentPage = index
                    return viewControllerAtIndex(index)
                }
            }
            return nil
    }

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

            if var index = pagesArray.indexOf(viewController.restorationIdentifier!){
                if index < pagesArray.count - 1 {
                    index++
                    return viewControllerAtIndex(index)
                }
            }
            return nil
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        pageControl.numberOfPages = 3
        pageControl.currentPage = 0
        pageControl.tintColor = UIColor.redColor()
        pageControl.pageIndicatorTintColor = UIColor.blackColor()
        pageControl.currentPageIndicatorTintColor = UIColor.orangeColor()

        if let vc = storyboard?.instantiateViewControllerWithIdentifier("MyPageViewController")
        {
            self.addChildViewController(vc)
            self.view.addSubview(vc.view)
            self.view.addSubview(pageControl)

            pageViewController = vc as! UIPageViewController
            pageViewController.dataSource = self
            pageViewController.delegate = self
            pageViewController.setViewControllers([viewControllerAtIndex(0)!], direction: .Forward, animated: true, completion: nil)
            pageViewController.didMoveToParentViewController(self)
        }
    }
}

Answer 1

尝试这个

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

     let identifier = viewController.restorationIdentifier

     self.index = self.identifiers.indexOfObject(identifier!)

     if index == identifiers.count - 1 {
          return nil
     }

     //increment the index to get the viewController before the current one
     self.index = self.index + 1

     return self.viewControllerAtIndex(self.index)

 }

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

      let identifier = viewController.restorationIdentifier

      self.index = self.identifiers.indexOfObject(identifier!)

      if index == 0 {

           return nil
      }

      //decrement the index to get the viewController before the current one
      self.index = self.index - 1

      return self.viewControllerAtIndex(self.index)

 }

  func presentationCountForPageViewController(pageViewController: UIPageViewController) -> Int 
 {
        return self.identifiers.count
 }

  func presentationIndexForPageViewController(pageViewController: UIPageViewController) -> Int 
 {
        return 0
 }