创建无限滚动天数的 UIPageViewController

Question

我的应用程序中有一个由 UIPageViewController 控制的日志。页面的视图控制器工作正常，但 UIPageViewController 有一些不稳定的行为。首先，委托方法（页面视图控制器是它自己的委托）：

private func journalPage(for date: Date) -> JournalViewController? {
    // Create a new view controller and pass suitable data.
    guard let journalPage = storyboard?.instantiateViewController(withIdentifier: JournalViewController.storyboardID) as? JournalViewController else {
        return nil
    }

    journalPage.date = date
    return journalPage
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
    guard let yesterday = calendar.date(byAdding: .day, value: -1, to: self.date) else {
        return nil
    }

    self.date = calendar.startOfDay(for: yesterday)        
    return journalPage(for: self.date)
}

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

    guard let tomorrow = calendar.date(byAdding: .day, value: 1, to: self.date) else {
        return nil
    }

    self.date = calendar.startOfDay(for: tomorrow)
    return journalPage(for: self.date)
}

我更新 UIPageViewController 的 date，然后 return 配置的期刊页面。问题是经常有重复的页面（同一日期的页面），或者跳过 page/date。我发现了 this 个问题，但不知道如何实现类似的问题。

我之前曾与 UIPageViewController 合作过，并且一直使用索引来解决这个问题，但在这种情况下，索引没有意义，因为您可以滚动到 beginning/end时间（字面意思）。

如何确保在正确的时间制作新页面以避免 duplicate/missed 日期？

Answer 1

我认为您必须以另一种方式对数据建模，因此创建一个包含数据数组的模型，并且（例如）使用索引访问数据以填充控制器。通过这种方式，您可以唯一地访问数据。

我是在基于 PageController 的应用程序中这样做的，从 apple 示例开始。

我有一个 class：（请参阅 apple 模板进行比较..）

class模型控制器：NSObject，UIPageViewControllerDataSource {

var myPages : [Page]?

.. }

其中 Page 是 class 描述您的单个页面。我这样修改苹果代码：

func viewControllerAtIndex(_ index: Int) -> BaseHWTestController? {
    // Return the data view controller for the given index.

    let count = selected.count
    if (count == 0) || (index >= count) {
        return nil
    }

    // Create a new view controller and pass suitable data.

    let myController = storyboard.instantiateViewController(withIdentifier: identifier) as! CustomPageController
    // set ref. to data inside the controller:
    BaseHWTestController.dataObject = myPages[index]
    return BaseHWTestController
}

Answer 2

不能用聚兰日数（JDN）作为索引号吗？

Answer 3

我没有使用索引就解决了这个问题（页面上的date 属性就足够了）。这会在任一方向上无限滚动，而不会创建重复项或跳过页面。

extension JournalPageViewController: UIPageViewControllerDataSource {
    /// Creates and returns a JournalViewController if it can be found in the storyboard,
    /// and sets it's date to `date`
    private func journalPage(for date: Date) -> JournalViewController? {
        // Create a new view controller and pass suitable data.
        guard let journalPage = storyboard?.instantiateViewController(withIdentifier: JournalViewController.storyboardID) as? JournalViewController else {
            return nil
        }

        journalPage.date = date
        return journalPage
    }

    func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
        debugPrint("Before: ", separator: "", terminator: "")
        let today = (viewController as! JournalViewController).date
        guard var yesterday = calendar.date(byAdding: .day, value: -1, to: today) else {
            return nil
        }
        yesterday = calendar.startOfDay(for: yesterday)

        return journalPage(for: yesterday)
    }

    func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
        debugPrint("After: ", separator: "", terminator: "")
        let today = (viewController as! JournalViewController).date
        guard var tomorrow = calendar.date(byAdding: .day, value: 1, to: today) else {
            return nil
        }
        tomorrow = calendar.startOfDay(for: tomorrow)

        return journalPage(for: tomorrow)
    }
}

extension JournalPageViewController: UIPageViewControllerDelegate {
    func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
        self.date = (self.viewControllers?.first as! JournalViewController).date
    }
}

创建无限滚动天数的 UIPageViewController

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