SwiftUI ScrollView滚动到相对位置

import SwiftUI

struct ContentView: View {
    @State private var offset: CGFloat = 0

    var body: some View {
        GeometryReader { geometry in
            ScrollView {
                VStack {
                    ForEach(0..<50) { index in
                        Text("Item \(index)")
                            .frame(height: 100)
                            .id(index)
                    }
                }
                .background(GeometryReader { proxy in
                    Color.clear.preference(key: ScrollOffsetPreferenceKey.self, value: -proxy.frame(in: .named("scroll")).origin.y)
                })
            }
            .coordinateSpace(name: "scroll")
            .onPreferenceChange(ScrollOffsetPreferenceKey.self) { value in
                offset = value
            }
            .frame(maxWidth: .infinity, maxHeight: .infinity)
            .background(GeometryReader { proxy in
                Color.clear
                    .preference(key: ScrollToPositionPreferenceKey.self, value: offset > 200 ? 200 : offset)
            })
        }
        .onPreferenceChange(ScrollToPositionPreferenceKey.self) { value in
            withAnimation(.spring()) {
                offset = value
            }
        }
    }
}

struct ScrollOffsetPreferenceKey: PreferenceKey {
    static var defaultValue: CGFloat = 0

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

struct ScrollToPositionPreferenceKey: PreferenceKey {
    static var defaultValue: CGFloat = 0

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