如何在SwiftUI中为列表创建按字母顺序排列的索引？

import SwiftUI

struct ContentView: View {
    let items = ["Apple", "Banana", "Cherry", "Durian", "Elderberry", "Fig", "Grape", "Honeydew", "Kiwi", "Lemon", "Mango", "Orange", "Peach", "Quince", "Raspberry", "Strawberry", "Tomato", "Watermelon"]
    let letters = Array(Set(items.map { String($0.prefix(1)).uppercased() })).sorted()

    var body: some View {
        NavigationView {
            List {
                ForEach(letters, id: \.self) { letter in
                    Section(header: Text(letter)) {
                        ForEach(items.filter { $0.hasPrefix(letter) }, id: \.self) { item in
                            Text(item)
                        }
                    }
                }
            }
            .listStyle(InsetGroupedListStyle())
            .navigationTitle("Fruit List")
            .overlay(IndexView(letters: letters))
        }
    }
}

struct IndexView: View {
    let letters: [String]

    var body: some View {
        VStack {
            Spacer()
            HStack {
                Spacer()
                ForEach(letters, id: \.self) { letter in
                    Text(letter)
                        .font(.footnote)
                        .padding(.trailing, 5)
                        .onTapGesture {
                            scrollTo(letter)
                        }
                }
            }
        }
        .padding(.vertical, 10)
        .padding(.horizontal, 20)
        .background(Color(.systemBackground).opacity(0.8))
        .cornerRadius(20)
        .padding(10)
    }

    private func scrollTo(_ letter: String) {
        // Scroll to the section with the given letter
        // Use ScrollViewReader and scrollTo methods
    }
}

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