UIPageViewController中的断言失败

我在UIPageViewController中有一个断言失败。

Assertion failure in -[UIPageViewController _flushViewController:animated:], /BuildRoot/Library/Caches/com.apple.xbs/Sources/UIKit/UIKit-3512.60.12/UIPageViewController.m Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Don't know about flushed view <UIView: 0x15a5bff30; frame = (0 0; 768 903); autoresize = W+H; layer = >' *** First throw call stack: (0x181ebedb0 0x181523f80 0x181ebec80 0x182844154 0x1877a1c40 0x1877a1da8 0x18784e9c4 0x18784ebfc 0x187852318 0x18784dd98 0x1870101e4 0x1849a2994 0x18499d5d0 0x1870270a4 0x10028b620 0x100348b78 0x100379f54 0x100168878 0x18733d568 0x1870330b4 0x1870f1a00 0x18733e71c 0x1870f832c 0x18703536c 0x18700f7ac 0x18700ed40 0x18700eba8 0x1873283b4 0x18700d5e8 0x18784ebd4 0x187852318 0x18784df3c 0x1871db550 0x1871daf6c 0x101c9b768 0x1849f0234 0x1849f00e8 0x182135e54 0x181e5d030 0x181e757d4 0x181e74f0c 0x181e72c64 0x181d9cc50 0x183684088 0x18707e088 0x10033b200 0x18193a8b8) libc++abi.dylib: terminating with uncaught exception of type NSException

我不知道为什么会出现这种错误。关于导致它的原因或如何调试它的任何线索？

运行此断言的直接方法是使用循环源为UIPageController定义滚动过渡样式。

当源包含两个页面时，每个页面是前一个页面，下一个页面是另一个页面。如果你滑动包含两个页面的UIPageController ，然后尝试设置3页的源代码，你将得到上面提到的断言，保证假设UIPageControllerDataSource在方法之前/之后允许在2页的情况下进行循环转换。

使用带滚动转换的UIPageController实现无崩溃的主要规则：

1）在调用setViewControllers方法之前设置dataSource

2）使用没有动画的setViewControllers方法（ animated: false ）

3）将单个页面模式的dataSource设置为nil

4）不允许2页模式的循环

所有这些建议共同使UIPageController绝对稳定。

 import UIKit /// Convenient subclass of UIPageViewController @objc class AMPageViewController: UIPageViewController { /// Turn on/off PageControl at the bottom @objc var showPageControl: Bool = true /// Array of all viewControllers @objc var source: [UIViewController]? { didSet { let count = source?.count ?? 0 if count > 0 { dataSource = count > 1 ? self : nil } else { dataSource = nil delegate = nil } } } /// Index of the current viewController from source @objc var pageIndex: Int { get { var currentPageIndex: Int = 0 if let vc = viewControllers?.first, let source = source, let pageIndex = source.index(of: vc) { currentPageIndex = pageIndex } return currentPageIndex } set { guard newValue >= 0, let source = source, newValue < source.count else { return } let vc = source[newValue] let direction: UIPageViewControllerNavigationDirection = newValue < pageIndex ? .reverse : .forward setViewController(vc, direction: direction) } } override weak var delegate: UIPageViewControllerDelegate? { get { return super.delegate } set { if source?.count ?? 0 > 0 { super.delegate = newValue } else { super.delegate = nil } } } /// Initializer in scroll-mode with interPageSpacing @objc init(navigationOrientation: UIPageViewControllerNavigationOrientation = .horizontal, interPageSpacing: Int = 0) { let options = (interPageSpacing > 0) ? [UIPageViewControllerOptionInterPageSpacingKey : 5] : nil super.init(transitionStyle: .scroll, navigationOrientation: navigationOrientation, options: options) } required init?(coder: NSCoder) { fatalError("init(coder:) has not been implemented") } /// Set viewcontroller by index from source @objc func setPageIndex(_ index: Int, completion: ((Bool) -> Void)? = nil) { guard index > 0, let source = source, index < source.count else { return } let vc = source[index] let direction: UIPageViewControllerNavigationDirection = index < pageIndex ? .reverse : .forward setViewController(vc, direction: direction, completion: completion) } private func setViewController(_ viewController: UIViewController, direction: UIPageViewControllerNavigationDirection = .forward, completion: ((Bool) -> Void)? = nil) { super.setViewControllers([viewController], direction: direction, animated: false, completion: completion) } } extension FFPageViewController: UIPageViewControllerDataSource { func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? { guard let source = source, let index = source.index(of: viewController) else { return nil } let count = source.count if count == 2, index == 0 { return nil } let prevIndex = (index - 1) < 0 ? count - 1 : index - 1 let pageContentViewController: UIViewController = source[prevIndex] return pageContentViewController } func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? { guard let source = source, let index = source.index(of: viewController) else { return nil } let count = source.count if count == 2, index == 1 { return nil } let nextIndex = (index + 1) >= count ? 0 : index + 1 let pageContentViewController = source[nextIndex] return pageContentViewController } func presentationCount(for pageViewController: UIPageViewController) -> Int { return showPageControl ? (source?.count ?? 0) : 0 } func presentationIndex(for pageViewController: UIPageViewController) -> Int { guard showPageControl else { return 0 } return pageIndex } }

可以在GitHub项目中找到的总体实现和用法示例。

当我在子控制器中有文本字段并且在滚动到下一个控制器时没有关闭键盘时，这也发生在我身上。如果是这种情况，只需在操作中添加endEditing，您可以在其中以编程方式更改控制器，或者如果您正在滚动页面ViewController的scrollViewDidScroll委托方法

如果您在代码中执行此操作，请在DispatchQueue.main.async块中移动pageViewController.setViewControllers函数调用。

我不知道它为什么有效，但它对我有用。以供参考。

当您的UIPageViewControllerTransitionStyle设置为scroll而不是pageCurl时会发生这种情况。

您是否动态创建视图控制器并在UIPageViewController上设置它们？在这种情况下，由于UIKit中的错误，您必须确保在第一次完成动画后调用setViewControllers的第二次调用。延迟发送是一种快速而肮脏的修复，但这不是一个好习惯

对我来说，问题是使用self.pageViewController作为当前视图控制器的成员而不是pageViewController作为在didFinishAnimating委托方法中获得的参数。