如何在AppKit上以自定义SwiftUI形式右对齐项目标签？

Question

我有以下可可形式：

struct Canvas: PreviewProvider {
  static var previews: some View {
    VStack {
      HStack(alignment: .firstTextBaseline) {
        Text("Endpoint:")
        TextField("https://localhost:8080/api", text: .constant(""))
      }
      Divider()
      HStack(alignment: .firstTextBaseline) {
        Text("Path:")
        TextField("/todos", text: .constant(""))
      }
      Spacer()
    }
    .padding()
    .previewLayout(.fixed(width: 280, height: 200))
  }
}

该面板看起来不错，但我想右对齐“ Endpoint：”和“ Path：”标签：

所以我应用了一个自定义的水平对齐方式：

struct Canvas: PreviewProvider {
  static var previews: some View {
    VStack(alignment: .label) {
      HStack(alignment: .firstTextBaseline) {
        Text("Endpoint:").alignmentGuide(.label) { $0[.trailing] }
        TextField("https://localhost:8080/api", text: .constant(""))
      }
      Divider()
      HStack(alignment: .firstTextBaseline) {
        Text("Path:").alignmentGuide(.label) { $0[.trailing] }
        TextField("/todos", text: .constant(""))
      }
      Spacer()
    }
    .padding()
    .previewLayout(.fixed(width: 280, height: 200))
  }
}

extension HorizontalAlignment {
  private enum Label: AlignmentID {
    static func defaultValue(in context: ViewDimensions) -> CGFloat {
      context[.leading]
    }
  }
  static let label: HorizontalAlignment = .init(Label.self)
}

结果不是我需要的：

没有文档，请帮助。

Answer 1

我不相信对齐指南将在其当前实施中起作用。在和他们玩了一会儿之后，似乎他们根据容器的给定大小来调整孩子的大小，然后根据指南对齐每个孩子。这会导致您看到的奇怪行为。

下面我展示了 3 种不同的技术，它们可以让您按复杂程度获得所需的结果。在这个特定示例之外，每个都有其应用。

label3()对于较长的形式，最后一个 ( ) 将是最可靠的。

struct ContentView: View {
    @State var sizes: [String:CGSize] = [:]

    var body: some View {
        VStack {
            HStack(alignment: .firstTextBaseline) {
                self.label3("Endpoint:")
                TextField("https://localhost:8080/api", text: .constant(""))
            }
            Divider()
            HStack(alignment: .firstTextBaseline) {
                self.label3("Path:")
                TextField("/todos", text: .constant(""))
            }
        }
        .padding()
        .onPreferenceChange(SizePreferenceKey.self) { preferences in
            self.sizes = preferences
        }
    }

    func label1(_ text: String) -> some View {
        Text(text) // Use a minimum size based on your best guess.  Look around and you'll see that many macOS apps actually lay forms out like this because it's simple to implement.
            .frame(minWidth: 100, alignment: .trailing)
    }

    func label2(_ text: String, sizer: String = "Endpoint:") -> some View {
        ZStack(alignment: .trailing) { // Use dummy content for sizing based on the largest expected item.  This can be great when laying out icons and you know ahead of time which will be the biggest.
            Text(sizer).opacity(0.0)
            Text(text)
        }
    }

    func label3(_ text: String) -> some View {
        Text(text) // Use preferences and save the size of each label
        .background(
            GeometryReader { proxy in
                Color.clear
                    .preference(key: SizePreferenceKey.self, value: [text : proxy.size])
            }
        )
        .frame(minWidth: self.sizes.values.map { $0.width }.max() ?? 0.0, alignment: .trailing)
    }
}

struct SizePreferenceKey: PreferenceKey {
    typealias Value = [String:CGSize]
    static var defaultValue: Value = [:]

    static func reduce(value: inout Value, nextValue: () -> Value) {
        let next = nextValue()
        for (k, v) in next {
            value[k] = v
        }
    }
}

这是带有label2或的结果的屏幕截图label3。