在Swift中使用PageViewController設置NSTimer

Question

我最近設置了一個ContainerView，它帶有一個PageViewController，這個PageViewController作爲我擁有的TableView頂部的一種橫幅瀏覽視圖（圖像）。現在，我很難將它連接到NSTimer（這樣它會自動循環瀏覽視圖/圖像）。除了我試圖連接的計時器部分之外，一切正常。我試圖轉換一些Objective-C教程/ SO問題，但仍然有困難。

我已經看過這個：Set timer to UIPageViewController，但我無法得到所提供的代碼爲我工作（或它的任何變化）。

請參閱以下我的代碼：

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] 
    } 

} 

任何幫助是極大的讚賞。

Answer 1

有兩點要注意：

1）總的想法是，你需要設置一個計時器在一些合理place-- viewWillAppear是一種常見的位置，記得要使它無效當視圖不再顯示（如viewWillDisappear）。如果不這樣做，可能會導致內存增長，因爲運行循環對目標有強烈的參考 - 在本例中爲self。我建議將您的NSTimer.scheduledTimer...調用移動到viewWillAppear。

2）上面的代碼animation非常簡單。基本上，你需要獲得當前的「頁面」，找出下一個「頁面」應該是什麼，然後讓你的UIPageViewController顯示下一個「頁面」。

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) 
} 

你也可以簡化您的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] 
}