swift - SwiftUI：单击按钮时如何呈现视图？

Question

我正在尝试使用 Apple 的SwiftUI制作一个应用程序，我需要有两个按钮在List一行中显示两个不同的视图。

我使用Xcode beta 7和MacOS Catalina beta 7。我试图添加一个Button呈现视图的视图，但是我无法单击它，当我尝试在一个简单Button的外部List并单击它时，AddList()视图没有出现。我也尝试过添加一个navigationButton内部navigationButton，但它也没有用。单击它时添加atapAction也不起作用，视图仍然没有出现

NavigationView {
            List(0..<5) { item in
                NavigationLink(destination: ContentOfList()) {
                    Text("hello") // dummy text
                    Spacer()
                    Text("edit")
                        .tapAction {
                            AddList() // This is the view I want to present
                    }
                }
                }.navigationBarItems(trailing: NavigationLink(destination: AddList(), label: { // doesn't work within navigationBarItems
                    Image(systemName: "plus.circle.fill")
                }))
        }

我希望AddList()视图会出现，但在这两种情况下，它不会出现。

Answer 1

更新： NavigationButton 的寿命很短。在 beta3 中，它已被弃用。我正在更新代码以使用其替换： NavigationLink。

您可以从所有三个位置呈现视图。就是这样：

import SwiftUI

struct ContentView: View {

    var body: some View {
        NavigationView {
            TopView().navigationBarTitle(Text("Top View"))
        }
    }
}

struct TopView: View {
    @State private var viewTypeA = true

    let detailViewA = DynamicNavigationDestinationLink(id: \String.self) { data in
            ListA(passedData: data)
    }

    let detailViewB = DynamicNavigationDestinationLink(id: \String.self) { data in
            ListB(passedData: data)
    }

    var body: some View {
            List(0..<5) { item in
                NavigationLink(destination: ListC(passedData: "FROM ROW #\(item)")) {
                    HStack {
                        Text("Row #\(item)")
                        Spacer()
                        Text("edit")
                            .tapAction {
                                self.detailViewA.presentedData?.value = "FROM TAP ACTION Row #\(item)"
                        }
                    }
                }
            }.navigationBarItems(trailing: Button(action: {
                            self.detailViewB.presentedData?.value = "FROM PLUS CIRCLE"
            }, label: {
                    Image(systemName: "plus.circle.fill")
                }))
    }
}

struct ListA: View {
    let passedData: String

    var body: some View {
        VStack {
            Text("VIEW A")
            Text(passedData)
        }
    }
}

struct ListB: View {
    let passedData: String

    var body: some View {
        VStack {
            Text("VIEW B")
            Text(passedData)
        }
    }
}

struct ListC: View {
    let passedData: String

    var body: some View {
        VStack {
            Text("VIEW C")
            Text(passedData)
        }
    }
}

Answer 2

大大改进的版本（SwiftUI、iOS 13 beta 7）

相同的解决方案适用于消除带有 .sheet 修饰符的模态。

import SwiftUI

struct DetailView: View {
    @Environment(\.presentationMode) var presentationMode: Binding<PresentationMode>
    var body: some View {
        Button(
            "Here is Detail View. Tap to go back.",
            action: { self.presentationMode.wrappedValue.dismiss() }
        )
    }
}

struct RootView: View {
    var body: some View {
        VStack {
            NavigationLink(destination: DetailView())
            { Text("I am Root. Tap for Detail View.") }
        }
    }
}

struct ContentView: View {
    var body: some View {
        NavigationView {
            RootView()
        }
    }
}

Answer 3

改良版。（斯威夫特，iOS 13 测试版 4）

class NavigationModel : BindableObject {
    var willChange = PassthroughSubject<Void, Never>()
    var presentedData: String? {
        didSet {
            willChange.send()
        }
    }
    func dismiss() { if presentedData != nil {
        presentedData = nil
    } }
}

struct ContentView: View {
    var body: some View {
        NavigationView {
            MasterView()
        }.environmentObject(NavigationModel())
    }
}

struct MasterView: View {

    @EnvironmentObject
    var navigationModel: NavigationModel
    var destinationLink = DynamicNavigationDestinationLink<String, String, DetailView>(id: \.self) { data in DetailView(data: data) }

    var body: some View {
        List(0..<10) { index in
            Button("I am root. Tap for more details of #\(index).") {
                self.navigationModel.presentedData = "#\(index)"
            }
        }
        .navigationBarTitle("Master")
        .onReceive(navigationModel.willChange) {
            self.destinationLink.presentedData?.value = self.navigationModel.presentedData
        }
    }
}

struct DetailView: View {
    @EnvironmentObject
    var model: NavigationModel

    let data: String

    var body: some View {
        Button("Here are details of \(data). Tap to go back.") {
            self.model.dismiss()
        }
        .navigationBarTitle("Detail \(data)")
    }
}

struct Empty : Hashable {
}


#if DEBUG
struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}
#endif