Question

我需要依赖具有PageView值的currentPage视图，以使PageView本身拥有该值的所有权（因此，@State ），但是当此值更改时，我需要更新应用状态。

使用TabView，我只需输入@Binding $selected作为参数，并可以使用自定义Binding<Int>对UI层之外的该值进行操作自己的getter和setter。这就是我现在正在尝试采用的解决方案。

但是我的PageView是基于UIHostingControllers和UIViewControllerRepresentable的数组，用于从UIKit集成UIPageViewController（我知道5.3中的Swift将通过以下方式提供SwiftUI版本： TabView，但我不想等到“ 9月”）

PageViewController.swift

// Source: https://stackoverflow.com/questions/58388071/how-to-implement-pageview-in-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: .scroll,
                navigationOrientation: .horizontal)
        pageViewController.dataSource = context.coordinator
        pageViewController.delegate = context.coordinator

        return pageViewController
    }

    func updateUIViewController(_ pageViewController: UIPageViewController, context: Context) {
        if controllers.count > 0 {
            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 parent.controllers.last
            }
            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 parent.controllers.first
            }
            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.swift

struct PageView<Page: View>: View {
    var viewControllers: [UIHostingController<Page>]

    var currentPage: Binding<Int>

    init(_ views: [Page], currentPage: Binding<Int>) {
        self.viewControllers = views.map {
            let ui = UIHostingController(rootView: $0)
            ui.view.backgroundColor = UIColor.clear
            return ui
        }

        self.currentPage = currentPage
    }

    var body: some View {
            ZStack(alignment: .bottom) {
                PageViewController(controllers: viewControllers, currentPage: currentPage)
                PageControl(numberOfPages: viewControllers.count, currentPage: currentPage)
            }.frame(height: 300)
    }
}

上面您可以看到我正在尝试从父视图Binding<Int>传递PageViewTest参数

PageViewTest.swift

struct PageViewTest: View {
    var pagesData = ["ONE", "TWO"]
    var _currentPage: Int = 0
    
    var currentPage: Binding<Int> {
        Binding<Int>(get: {
            self._currentPage
        }, set: {
            // i.e. Update app state
            print($0)
        })
    }

    var body: some View {
        VStack {
            PageView(pagesData.map {
                Text($0)
            }, currentPage: self.currentPage)
        }
    }
}

此设置的工作范围高达调用PageViewTest中指定的setter例程，但是由于某种原因，绑定未反映在符合PageControl的{{1}}（来自PageView.swift）中，因此我觉得这不是解决方案。

我错误地绕过了绑定吗？ PageView应该拥有UIViewRepresentable的状态，但我希望其祖先视图能够对它进行更改。

@ObservableObject将不起作用，因为我只想发送一个原语。 currentPage / CurrentValueSubject不会触发（大概是因为PageView会一遍又一遍地重新初始化）：

备用PageView.swift

Passthrough

从父视图传递绑定到符合UIViewControllerRepresentable的子视图

0 个答案: