SwiftUI 也在 ScrollView 中创建自定义分段控件

Question

下面是我创建标准分段控件的代码。

struct ContentView: View {

    @State private var favoriteColor = 0
    var colors = ["Red", "Green", "Blue"]

    var body: some View {
        VStack {
            Picker(selection: $favoriteColor, label: Text("What is your favorite color?")) {
                ForEach(0..<colors.count) { index in
                    Text(self.colors[index]).tag(index)
                }
            }.pickerStyle(SegmentedPickerStyle())

            Text("Value: \(colors[favoriteColor])")
        }
    }
}

我的问题是如何修改它以具有自定义的分段控件，在其中我可以将边框与我自己的颜色一起四舍五入，因为使用 UIKit 很容易做到这一点？有没有人这样做过。

我的完美示例是 Uber eats 应用程序，当您 select 一家餐厅时，您可以通过 select 在自定义分段控件中选择一个选项来滚动到菜单的特定部分。

包括我希望自定义的元素：

* 更新 *

最终设计图

Answer 1

如果我正确地回答了这个问题，那么起点可能类似于下面的代码。显然，样式需要注意一下。这具有用于段的硬连线宽度。为了更加灵活，您需要使用几何 Reader 来衡量可用的内容并划分 space.

struct ContentView: View {

      @State var selection = 0

      var body: some View {

            let item1 = SegmentItem(title: "Some Way", color: Color.blue, selectionIndex: 0)
            let item2 = SegmentItem(title: "Round Zip", color: Color.red, selectionIndex: 1)
            let item3 = SegmentItem(title: "Multi-City", color: Color.green, selectionIndex: 2)

            return VStack() {
                  Spacer()
                  Text("Selected Item: \(selection)")
                  SegmentControl(selection: $selection, items: [item1, item2, item3])
                  Spacer()
            }
      }
}


struct SegmentControl : View {

      @Binding var selection : Int
      var items : [SegmentItem]

      var body : some View {

            let width : CGFloat = 110.0

            return HStack(spacing: 5) {
                  ForEach (items, id: \.self) { item in
                        SegmentButton(text: item.title, width: width, color: item.color, selectionIndex: item.selectionIndex, selection: self.$selection)
                  }
            }.font(.body)
                  .padding(5)
                  .background(Color.gray)
                  .cornerRadius(10.0)
      }
}


struct SegmentButton : View {

      var text : String
      var width : CGFloat
      var color : Color
      var selectionIndex = 0
      @Binding var selection : Int

      var body : some View {
            let label = Text(text)
                  .padding(5)
                  .frame(width: width)
                  .background(color).opacity(selection == selectionIndex ? 1.0 : 0.5)
                  .cornerRadius(10.0)
                  .foregroundColor(Color.white)
                  .font(Font.body.weight(selection == selectionIndex ? .bold : .regular))

            return Button(action: { self.selection = self.selectionIndex }) { label }
      }
}


struct SegmentItem : Hashable {
      var title : String = ""
      var color : Color = Color.white
      var selectionIndex = 0
}


struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

Answer 2

这是您要找的吗？

import SwiftUI

struct CustomSegmentedPickerView: View {
  @State private var selectedIndex = 0
  private var titles = ["Round Trip", "One Way", "Multi-City"]
  private var colors = [Color.red, Color.green, Color.blue]
  @State private var frames = Array<CGRect>(repeating: .zero, count: 3)

  var body: some View {
    VStack {
      ZStack {
        HStack(spacing: 10) {
          ForEach(self.titles.indices, id: \.self) { index in
            Button(action: { self.selectedIndex = index }) {
              Text(self.titles[index])
            }.padding(EdgeInsets(top: 16, leading: 20, bottom: 16, trailing: 20)).background(
              GeometryReader { geo in
                Color.clear.onAppear { self.setFrame(index: index, frame: geo.frame(in: .global)) }
              }
            )
          }
        }
        .background(
          Capsule().fill(
            self.colors[self.selectedIndex].opacity(0.4))
            .frame(width: self.frames[self.selectedIndex].width,
                   height: self.frames[self.selectedIndex].height, alignment: .topLeading)
            .offset(x: self.frames[self.selectedIndex].minX - self.frames[0].minX)
          , alignment: .leading
        )
      }
      .animation(.default)
      .background(Capsule().stroke(Color.gray, lineWidth: 3))

      Picker(selection: self.$selectedIndex, label: Text("What is your favorite color?")) {
        ForEach(0..<self.titles.count) { index in
          Text(self.titles[index]).tag(index)
        }
      }.pickerStyle(SegmentedPickerStyle())

      Text("Value: \(self.titles[self.selectedIndex])")
      Spacer()
    }
  }

  func setFrame(index: Int, frame: CGRect) {
    self.frames[index] = frame
  }
}


struct CustomSegmentedPickerView_Previews: PreviewProvider {
  static var previews: some View {
    CustomSegmentedPickerView()
  }
}

Answer 3

None 上述解决方案对我有用，因为 GeometryReader returns 不同的值一旦放置在导航视图中，就会在后台抛出活动指示器的定位。我找到了替代解决方案，但它们只适用于固定长度的菜单字符串。也许有一个简单的修改可以使上面的代码贡献工作，如果是这样，我会渴望阅读它。如果您遇到与我相同的问题，那么这可能对您有用。

感谢 Reddit 用户“End3r117”和这篇 SwiftWithMajid 文章 https://swiftwithmajid.com/2020/01/15/the-magic-of-view-preferences-in-swiftui/ 的启发，我得以设计出一个解决方案。这可以在 NavigationView 内部或外部工作，并接受各种长度的菜单项。

struct SegmentMenuPicker: View {
    var titles: [String]
    var color: Color
    
    @State private var selectedIndex = 0
    @State private var frames = Array<CGRect>(repeating: .zero, count: 5)

    var body: some View {
        VStack {
            ZStack {
                HStack(spacing: 10) {
                    ForEach(self.titles.indices, id: \.self) { index in
                        Button(action: {
                            print("button\(index) pressed")
                            self.selectedIndex = index
                        }) {
                            Text(self.titles[index])
                                .foregroundColor(color)
                                .font(.footnote)
                                .fontWeight(.semibold)
                        }
                        .padding(EdgeInsets(top: 0, leading: 5, bottom: 0, trailing: 5))
                        .modifier(FrameModifier())
                        .onPreferenceChange(FramePreferenceKey.self) { self.frames[index] = [=10=] }
                    }
                }
                .background(
                    Rectangle()
                        .fill(self.color.opacity(0.4))
                        .frame(
                            width: self.frames[self.selectedIndex].width,
                            height: 2,
                            alignment: .topLeading)
                        .offset(x: self.frames[self.selectedIndex].minX - self.frames[0].minX, y: self.frames[self.selectedIndex].height)
                    , alignment: .leading
                )
            }
            .padding(.bottom, 15)
            .animation(.easeIn(duration: 0.2))

            Text("Value: \(self.titles[self.selectedIndex])")
            Spacer()
        }
    }
}

struct FramePreferenceKey: PreferenceKey {
    static var defaultValue: CGRect = .zero

    static func reduce(value: inout CGRect, nextValue: () -> CGRect) {
        value = nextValue()
    }
}

struct FrameModifier: ViewModifier {
    private var sizeView: some View {
        GeometryReader { geometry in
            Color.clear.preference(key: FramePreferenceKey.self, value: geometry.frame(in: .global))
        }
    }

    func body(content: Content) -> some View {
        content.background(sizeView)
    }
}

struct NewPicker_Previews: PreviewProvider {
    static var previews: some View {
        VStack {
            SegmentMenuPicker(titles: ["SuperLongValue", "1", "2", "Medium", "AnotherSuper"], color: Color.blue)
            NavigationView {
                SegmentMenuPicker(titles: ["SuperLongValue", "1", "2", "Medium", "AnotherSuper"], color: Color.red)
            }
        }
    }
}

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