SwiftUI UIPageView 编译错误和操作表问题

Question

我的代码中有 2 个问题。

一个是编译错误[无法将类型'Page1'的值转换为预期的元素类型'_']显示在★。

另一个是当按下后退按钮时，Page2（蓝色）在显示警报表时消失。 （注释掉“Page1(page: self.$page)”，然后构建源代码） 预期的行为是 Page2（蓝色）在按下警报按钮（是）之前不会消失。

谁能告诉我如何解决这些问题？

import SwiftUI

struct PageViewController: UIViewControllerRepresentable {
    var controllers: [UIViewController]
    @Binding var currentPage: Int

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

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

        return pageViewController
    }

    func updateUIViewController(_ pageViewController: UIPageViewController, context: Context) {
        pageViewController.setViewControllers(
            [controllers[currentPage]], direction: .forward, 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
            }
        }
    }
}


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)
    }
}


struct ContentView: View {
    @State var page: Int = 0

    var body: some View {
        VStack {
            PageView([
                Page1(page: self.$page), // ★ error
                Page2(page: self.$page)// ★ error
            ], currentPage: $page)
        }
    }
}


struct Page1: View{
    @Binding var page: Int
    var body: some View {
        ZStack{
            Color.red
            VStack{
                Text("page1")
                Button (
                    action: { self.page += 1 }
                ){
                    Image(systemName: "forward")
                        .accentColor(Color.yellow)
                }
            }
        }
    }
}


struct Page2: View{
    @State private var showingAlert: Bool = false
    @Binding var page: Int
    var body: some View {
        ZStack{
            Color.blue
            VStack{
                Text("page2")
                Button (
                    action: { self.showingAlert.toggle() }
                ){
                    Image(systemName: "backward")
                        .accentColor(Color.yellow)
                }
            }
            .alert(isPresented: $showingAlert) {
                Alert(
                    title: Text("Confirm"),
                    message: Text("Back?"),
                    primaryButton:
                    .default(Text("Yes"),
                             action:{ self.page -= 1 }
                    ),
                    secondaryButton:
                    .cancel(Text("No"))
                )//alert
            }//alert
        }
    }
}

Answer 1

我能够使用：

[如何在 SwiftUI #1 中创建引导屏幕 - 嵌入 UIPageViewController] (https://www.blckbirds.com/post/how-to-create-a-onboarding-screen-in-swiftui-1)