tvOS上的SwiftUI：如何知道在列表中选择了哪个项目

Question

在列表中，我需要知道选择了哪个项目，并且该项目必须是可单击的。

这是我尝试做的事情：

| item1 | info of the item3 (selected) |
| item2 |                              |
|*item3*|                              |
| item4 |                              |

我可以用.focusable()来做到这一点，但它不可点击。

[Button或NavigationLink有效，但我无法选择当前项目。

[当您使用Button或NavigationLink .focusable时，请勿再击打。

所以我的问题是：

我如何选择当前项目（以便我可以显示有关该项目的更多信息）并使之可单击以显示下一个视图？

示例代码1：可聚焦，但在tvOS上不存在.onTap

import SwiftUI

struct TestList: Identifiable {
    var id: Int
    var name: String
}

let testData = [Int](0..<50).map { TestList(id: $0, name: "Row \($0)")  }


struct SwiftUIView : View {
    var testList: [TestList]

    var body: some View {
        List {
            ForEach(testList) { txt in
                TestRow(row: txt)
            }
        }
    }
}

struct TestRow: View {
    var row: TestList

    @State private var backgroundColor = Color.clear

    var body: some View {
        Text(row.name)
        .focusable(true) { isFocused in
            self.backgroundColor = isFocused ? Color.green : Color.blue
            if isFocused {
                print(self.row.name)
            }
        }
        .background(self.backgroundColor)
    }
}

示例代码2：可通过NavigationLink单击项目，但无法获取所选项目，并且不再调用.focusable。

import SwiftUI

struct TestList: Identifiable {
    var id: Int
    var name: String
}

let testData = [Int](0..<50).map { TestList(id: $0, name: "Row \($0)")  }


struct SwiftUIView : View {
    var testList: [TestList]

    var body: some View {
        NavigationView {
            List {
                ForEach(testList) { txt in
                    NavigationLink(destination: Text("Destination")) {
                        TestRow(row: txt)
                    }
                }
            }
        }
    }
}

struct TestRow: View {
    var row: TestList

    @State private var backgroundColor = Color.clear

    var body: some View {
        Text(row.name)
        .focusable(true) { isFocused in
            self.backgroundColor = isFocused ? Color.green : Color.blue
            if isFocused {
                print(self.row.name)
            }
        }
        .background(self.backgroundColor)
    }
}

Answer 1

在我看来，您似乎无法在tift的swiftui中附加点击事件，这对我来说似乎是一个主要的网站。我提出了一个可让您将大多数swiftui组件设为可选择和可点击的hack方法。希望对您有所帮助。

首先，我需要制作一个捕获事件的UIView。

    class ClickableHackView: UIView {
        weak var delegate: ClickableHackDelegate?

        override init(frame: CGRect) {
            super.init(frame: frame)        
        }

        override func pressesEnded(_ presses: Set<UIPress>, with event: UIPressesEvent?) {
            delegate?.clicked()
        }

        override func didUpdateFocus(in context: UIFocusUpdateContext, with coordinator: UIFocusAnimationCoordinator) {
            delegate?.focus(focused: isFocused)
        }

        required init?(coder: NSCoder) {
            fatalError("init(coder:) has not been implemented")
        }

        override var canBecomeFocused: Bool {
            return true
        }
    }

可点击的委托人：

protocol ClickableHackDelegate: class {
    func focus(focused: Bool)
    func clicked()
}

然后为我的视图添加swiftui扩展名

struct ClickableHack: UIViewRepresentable {
    @Binding var focused: Bool
    let onClick: () -> Void

    func makeUIView(context: UIViewRepresentableContext<ClickableHack>) -> UIView {
        let clickableView = ClickableHackView()
        clickableView.delegate = context.coordinator
        return clickableView
    }

    func updateUIView(_ uiView: UIView, context: UIViewRepresentableContext<ClickableHack>) {
    }

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

    class Coordinator: NSObject, ClickableHackDelegate {
        private let control: ClickableHack

        init(_ control: ClickableHack) {
            self.control = control
            super.init()
        }

        func focus(focused: Bool) {
            control.focused = focused
        }

        func clicked() {
            control.onClick()
        }
    }
}

然后，我制作了一个友好的swiftui包装器，这样我就可以传入我希望成为可聚焦和可点击的任何类型的组件

struct Clickable<Content>: View where Content : View {
    let focused: Binding<Bool>
    let content: () -> Content
    let onClick: () -> Void

    @inlinable public init(focused: Binding<Bool>, onClick: @escaping () -> Void, @ViewBuilder content: @escaping () -> Content) {
        self.content = content
        self.focused = focused
        self.onClick = onClick
    }

    var body: some View {
        ZStack {
            ClickableHack(focused: focused, onClick: onClick)
            content()
        }
    }
}

示例用法：

struct ClickableTest: View {
    @State var focused1: Bool = false
    @State var focused2: Bool = false

    var body: some View {
        HStack {
            Clickable(focused: self.$focused1, onClick: {
                print("clicked 1")
            }) {
                Text("Clickable 1")
                    .foregroundColor(self.focused1 ? Color.red : Color.black)
            }
            Clickable(focused: self.$focused2, onClick: {
                print("clicked 2")
            }) {
                Text("Clickable 2")
                    .foregroundColor(self.focused2 ? Color.red : Color.black)
            }
        }
    }
}