在Swift中使用PageViewController设置NSTimer

Question

我最近设置了一个ContainerView，它带有一个PageViewController，这个PageViewController作为我拥有的TableView顶部的一种横幅浏览视图（图像）。现在，我很难将它连接到NSTimer（这样它会自动循环浏览视图/图像）。除了我试图连接的计时器部分之外，一切正常。我试图转换一些Objective-C教程/ SO问题，但仍然有困难。

我已经看过这个：Set timer to UIPageViewController，但我无法得到所提供的代码为我工作（或它的任何变化）。

请参阅以下我的代码：

class ImageSwapViewController: UIPageViewController { 

    private(set) lazy var orderedViewControllers: [UIViewController] = { 
     return [self.newColoredViewController("First"), 
     self.newColoredViewController("Second"), 
     self.newColoredViewController("Third")] 
    }() 

    private func newColoredViewController(order: String) -> UIViewController { 
     return UIStoryboard(name: "Main", bundle: nil) . 
     instantiateViewControllerWithIdentifier("\(order)ViewController") 
    } 

    override func viewDidLoad() { 
     super.viewDidLoad() 

     // Do any additional setup after loading the view. 

     self.dataSource = self 

     if let firstViewController = orderedViewControllers.first { 
     setViewControllers([firstViewController], 
      direction: .Forward, 
      animated: true, 
      completion: nil) 
    } 

     NSTimer.scheduledTimerWithTimeInterval(2, target: self, selector: #selector(ImageSwapViewController.animation), userInfo: nil, repeats: true) 
    } 

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

    func animation() { 
     [NEED HELP WITH WHAT GOES HERE] 
    } 
} 

extension ImageSwapViewController : UIPageViewControllerDataSource { 

    func pageViewController(pageViewController: UIPageViewController, 
     viewControllerBeforeViewController viewController: UIViewController) -> UIViewController? { 
      guard let viewControllerIndex = orderedViewControllers.indexOf(viewController) else { 
       return nil 
      } 

      let previousIndex = viewControllerIndex - 1 

      guard previousIndex >= 0 else { 
       return orderedViewControllers.last 
      } 

      guard orderedViewControllers.count > previousIndex else { 
       return nil 
      } 

      return orderedViewControllers[previousIndex] 
    } 

    func pageViewController(pageViewController: UIPageViewController, 
     viewControllerAfterViewController viewController: UIViewController) -> UIViewController? { 
      guard let viewControllerIndex = orderedViewControllers.indexOf(viewController) else { 
       return nil 
      } 

      let nextIndex = viewControllerIndex + 1 
      let orderedViewControllersCount = orderedViewControllers.count 

      guard orderedViewControllersCount != nextIndex else { 
       return orderedViewControllers.first 
      } 

      guard orderedViewControllersCount > nextIndex else { 
       return nil 
      } 

      return orderedViewControllers[nextIndex] 
    } 

} 

任何帮助是极大的赞赏。

Answer 1

有两点要注意：

1）总的想法是，你需要设置一个计时器在一些合理place-- viewWillAppear是一种常见的位置，记得要使它无效当视图不再显示（如viewWillDisappear）。如果不这样做，可能会导致内存增长，因为运行循环对目标有强烈的参考 - 在本例中为self。我建议将您的NSTimer.scheduledTimer...调用移动到viewWillAppear。

2）上面的代码animation非常简单。基本上，你需要获得当前的“页面”，找出下一个“页面”应该是什么，然后让你的UIPageViewController显示下一个“页面”。

func animation() { 
    guard let currentViewController = viewControllers?.first else { 
     return 
    } 

    // Use delegate method to retrieve the next view controller 
    guard let nextViewController = pageViewController(self, viewControllerAfterViewController: currentViewController) else { 
     return 
    } 
    setViewControllers([nextViewController], direction: .Forward, animated: true, completion: nil) 
} 

你也可以简化您的before和after方法略有：

func pageViewController(pageViewController: UIPageViewController, viewControllerAfterViewController viewController: UIViewController) -> UIViewController? { 
    guard let i = orderedViewControllers.indexOf(viewController) else { 
     return nil 
    } 
    let nextIndex = (i + 1) % AutoAnimatingPageViewController.colors.count 
    return orderedViewControllers[nextIndex] 
} 

func pageViewController(pageViewController: UIPageViewController, viewControllerBeforeViewController viewController: UIViewController) -> UIViewController? { 
    guard let i = orderedViewControllers.indexOf(viewController) else { 
     return nil 
    } 
    let prevIndex = (i - 1) < 0 ? AutoAnimatingPageViewController.colors.count - 1 : (i - 1) 
    return orderedViewControllers[prevIndex] 
}