SwiftUI 工作表中未触发深层链接 onChange

Question

我的 SwiftUI 应用中的深层链接存在问题。

在我的应用程序类中，我已将 deepLink 声明为层次结构中 ContentView() 下每个视图的环境变量：

...

@main
struct TestApp: App {

var userSettings: UserSettings
var dataFetcher: DataFetcher
var dataUpdater: DataUpdater

@State var deepLink = ""

init() {
    userSettings = UserSettings()
    dataFetcher = DataFetcher(userSettings: userSettings)
    dataUpdater = DataUpdater(userSettings: userSettings)
}

var body: some Scene {
    WindowGroup {
        ContentView()
                .environmentObject(userSettings)
                .environmentObject(dataFetcher)
                .environmentObject(dataUpdater)
                .onOpenURL { url in
                    deepLink = url.absoluteString
                }
                .environment(\.deepLink, deepLink)
    }
}

}

在我的 ContentView() 中，我将 deepLink 声明为环境变量

struct ContentView: View {

    ...

    @State var isTestSheetViewPresented = false

    @Environment(\.deepLink) var deepLink: String

    ...

    var body: some View {

        Button(action: {
            self.isTestSheetViewPresented = true
        }, label: {
            HStack {
                Spacer()
                Image(systemName: "plus")
                Text("Add")
                Spacer()
            }
        })
        .sheet(isPresented: $isTestSheetViewPresented, content: {
            TestSheetView(isPresented: self.$isTestSheetViewPresented)
        })
        .onChange(of: self.deepLink) { _ in
            self.isTestSheetViewPresented = true
        }
    }

}

而TestSheetView是这样的

struct TestSheetView: View {

    @Environment(\.deepLink) var deepLink: String

    @State var url: String = ""

    var body: some View {
        Text(url)
            .onChange(of: deepLink) { _ in
                if deepLink != "" {
                    self.url = deepLink
                }
            }
    }

}

问题是，当我点击一个链接并打开我的应用程序时，TestSheetView 会正确显示，但除非我向下滚动一点，否则不会触发 onChange。

相反，如果我将 TestSheetView 的相同代码放在 ContentView 中，则文本会正确显示

Answer 1

似乎是时间问题。在初始化 TestSheetView 时，主体是在 deepLink 更改之后创建的，因此它无法检测到它。

解决方案是在TestSheetView 中使用onAppear 并从那里读取，如下所示：

struct TestSheetView: View {

    @Environment(\.deepLink) var deepLink: String

    @State var url: String = ""

    var body: some View {
        Text(url)
            .onAppear {
                if deepLink != "" {
                    self.url = deepLink
                }
            }
    }
}

Answer 2

同时处理视图尚未出现的情况和链接正在视图中导航的情况都是不符合人体工程学的。以下视图修饰符处理这两种情况。它假定顶级导航视图中的 .onOpenURL() 处理程序设置当前选项卡选择以及 currentDeepLink 环境值。

struct DeepLinkViewModifier: ViewModifier {
    @Environment(\.currentDeepLink) private var currentDeepLink
    let action: ((URL) -> Bool)

    func body(content: Content) -> some View {
        content
            .onAppear {
                if let url = currentDeepLink.wrappedValue,
                    action(url) {
                    currentDeepLink.wrappedValue = nil
                }
            }
            .onOpenURL { url in
                _ = action(url)
            }
    }
}

extension View {
    func onDeepLink(perform action: @escaping ((URL) -> Bool)) -> some View {
        return self.modifier(DeepLinkViewModifier(action: action))
    }
}

用途：

struct SomeView: View {
    @State urlString: String = ""

    var body: some View {
        Text(urlString).onDeepLink { url
            self.string = url.absoluteString
            return true // return false if another handler should consume
        }
    }
}

struct ContentView: View {
    @State private var tabSelection: TabSelection = .something
    @State private var currentDeepLink: URL? = nil

    var body: some View {
        TabView(selection: self.$tabSelection) {
        ...
        }
        .onOpenURL { url in
             self.tabSelection = ... // determine selection from URL
             self.currentDeepLink = url
        }
        .environment(\.tabSelection, self.$tabSelection)
        .environment(\.currentDeepLink, self.$currentDeepLink)
    }
}