UIPageViewController 添加第三页后显示错误的页面

Question

在我的项目中，我有一个 UIPageViewController，用户可以向它添加新页面（它从一页开始）。每次用户添加新页面时，UIPageViewController 必须显示当前页面（用户必须在最后一页，以便他/她可以添加新页面）。添加第二页后一切正常，但是当用户在 page2 并添加第三页并向前滚动时，UIPageViewController 显示第一页而不是显示第三页（出于某种原因，我不知道，如果用户向后滚动一切正常和 UIPageViewController 显示 page1)。

这是我添加新页面的代码：

class HomePageVC: UIPageViewController {

    private var pages = [SomeVC]()
    private var currentSomeVC: SomeVC!

    override func viewDidLoad() {
        super.viewDidLoad()
    
        view.backgroundColor = .clear
    
        dataSource = self
        delegate = self
        
        let someVC = SomeVC()
        pages.append(someVC)

        if pages.count != 0 {
            currentSomeVC = pages[0]
            setViewControllers(pages, direction: .forward, animated: true, completion: nil)
        }
    
        if pages.count == 1 {
        
            delegate = nil
            dataSource = nil
        }
    }

    func addNewPage() {
        
        let someVC = SomeVC()
        pages.append(someVC)
        
        if delegate == nil, dataSource == nil {
            delegate = self
            dataSource = self
        }
    }
}

extension HomePageVC: UIPageViewControllerDelegate, UIPageViewControllerDataSource {

    func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
        guard let viewControllerIndex = pages.firstIndex(of: viewController as! SomeVC) else {
            return nil
        }
    
            let previousIndex = viewControllerIndex - 1
    
        guard previousIndex >= 0 else {
            return pages.last
        }
    
        guard pages.count > previousIndex else {
            return nil
        }
    
        return pages[previousIndex]
    }

    func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
        guard let viewControllerIndex = pages.firstIndex(of: viewController as! SomeVC) else {
            return nil
        }
    
        let nextIndex = viewControllerIndex + 1
    
        guard pages.count != nextIndex else {
            return pages.first
        }
    
        guard pages.count > nextIndex else {
            return nil
        }
    
        return pages[nextIndex]
    }

    func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
    
        if completed {
        
            guard let viewControllerIndex = pages.firstIndex(of: pageViewController.viewControllers?.first as! SomeVC), let viewController = pageViewController.viewControllers?.first as? SomeVC else {
                return
            }
            currentSomeVC = viewController
        }
    }
}

Answer 1

尝试将您的 addNewPage() 方法替换为以下内容：

func addNewPage() {
        
        let someVC = SomeVC()
        pages.append(someVC)
        
        if delegate == nil, dataSource == nil {
            delegate = self
            dataSource = self
        }
        setViewControllers([pages[pages.count-1]], direction: .forward, animated: true, completion: nil)
    }

您正在向 pageViewController 添加新的 viewController，但没有将 pageViewController 设置为新创建的。

希望它对你有用。

Answer 2

重新加载 UIPageViewController，

func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
    if !completed { return }
    DispatchQueue.main.async() {
        self.dataSource = nil
        self.dataSource = self
    }
}