SwiftUI：单击按钮时如何显示视图？

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呈现视图但是，我无法点击它，当我尝试在一个简单的Button外部List并点击它时，该AddList()视图没有出现。我也试过添加一个navigationButton内部，navigationButton但它也不起作用。tapAction单击它时添加一个也不起作用，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()视图出现，但在这两种情况下，它没有。

Answer 1

更新： NavigationButton 的寿命很短。在 beta3 中它已经被弃用了。我正在更新代码以使用其替代品： 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使用 .sheet 修饰符呈现的模态。

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()
        }
    }
}