Question

我在SwiftUI中使用this UIPageViewController implementation作为起点，但是当currentPage为时，我想在PageView的上方或下方显示一个视图（例如：“ OK”文本或按钮）最后一页。

无论何时，我每次在PageView上方或下方添加if语句时，只要滑到第二页，所有其他页面都将被删除，并且无法在页面之间滑动。如果我剔除if逻辑，则一切正常。这是代码：

PageViewController：

struct PageViewController: UIViewControllerRepresentable {
    var controllers: [UIViewController]

    @Binding var currentPage: Int

    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }

    func makeUIViewController(context: Context) -> UIPageViewController {
        let pageViewController = UIPageViewController(
            transitionStyle: .scroll,
            navigationOrientation: .horizontal)
        pageViewController.dataSource = context.coordinator
        pageViewController.delegate = context.coordinator

        return pageViewController
    }

    func updateUIViewController(_ pageViewController: UIPageViewController, context: Context) {
        var dir = UIPageViewController.NavigationDirection.forward
        if let visibleViewController = pageViewController.viewControllers?.first,
            let nextPage = controllers.firstIndex(of: visibleViewController) {
            if currentPage < nextPage {
                dir = .reverse
            }
        }

        pageViewController.setViewControllers([controllers[currentPage]], direction: dir, animated: true)
    }

    class Coordinator: NSObject, UIPageViewControllerDataSource, UIPageViewControllerDelegate {
        var parent: PageViewController

        init(_ pageViewController: PageViewController) {
            self.parent = pageViewController
        }

        func pageViewController(
            _ pageViewController: UIPageViewController,
            viewControllerBefore viewController: UIViewController) -> UIViewController?
        {
            guard let index = parent.controllers.firstIndex(of: viewController) else {
                return nil
            }
            if index == 0 {
                return nil
            }
            return parent.controllers[index - 1]
        }

        func pageViewController(
            _ pageViewController: UIPageViewController,
            viewControllerAfter viewController: UIViewController) -> UIViewController?
        {
            guard let index = parent.controllers.firstIndex(of: viewController) else {
                return nil
            }
            if index + 1 == parent.controllers.count {
                return nil
            }
            return parent.controllers[index + 1]
        }

        func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
            if completed,
                let visibleViewController = pageViewController.viewControllers?.first,
                let index = parent.controllers.firstIndex(of: visibleViewController)
            {
                parent.currentPage = index
            }
        }
    }
}

PageView：

struct PageView<Page: View>: View {
    var viewControllers: [UIHostingController<Page>]
    @Binding var currentPage: Int

    init(_ views: [Page], currentPage: Binding<Int>) {
        self._currentPage = currentPage
        self.viewControllers = views.map { UIHostingController(rootView: $0) }
    }

    var body: some View {
        PageViewController(controllers: viewControllers, currentPage: $currentPage).frame(width: UIScreen.main.bounds.width)
    }
}

主要ContentView：

struct TestView: View {
    @State private var curPage: Int = 0

    var body: some View {
        ZStack {
            Color(.secondarySystemBackground)

            VStack {
                if curPage == 9892832 {
                    Text("OK").padding().foregroundColor(.blue).padding(.top, 60)
                }

                PageView([
                    Text("Page 1"),
                    Text("Page 2"),
                    Text("Page 3"),
                    Text("Page 4")
                ], currentPage: $curPage)
            }

        }.edgesIgnoringSafeArea(.all)
    }
}

struct TestView_Previews: PreviewProvider {
    static var previews: some View {
        TestView()
    }
}

我无法确定这是SwiftUI错误还是使用UIViewControllerRepresentable的副作用。其他人看到带有条件视图吗？有任何解决方法的想法吗？

Answer 1

我不知道此问题的根本原因是什么。但是我用两个嵌套的VStack解决了这个问题。将您的PageView放在内部，并将您的if或其他视图放在外部VStack。

VStack {
    if curPage == 9892832 {
                Text("OK").padding().foregroundColor(.blue).padding(.top, 60)
    }

    VStack {

        PageView([
                Text("Page 1"),
                Text("Page 2"),
                Text("Page 3"),
                Text("Page 4")
            ], currentPage: $curPage)
    }

}

PageView（UIPageViewController）的条件同级中断分页

1 个答案: