使用PreferenceKey是可行的（感谢@jnpdx的建议）。如果其他人想知道如何做到这一点，下面是完整的实现：

struct ContentView: View {
    
    @State var frames = [Int: CGRect]()
    
    var body: some View {
        
        ScrollView {
            LazyVStack {
                ForEach((1...10), id: \.self) { itemID in
                    ItemView(value: itemID)
                        .modifier(FrameModifier())
                        .onLongPressGesture {
                            print(frames[itemID])
                        }
                        .onPreferenceChange(FramePreferenceKey.self) {
                            frames[itemID] = $0
                        }
                }
            }
        }
    }
}

struct ItemView: View {
    
    let value: Int
    
    var body: some View {
        Text("\(value)")
            .frame(height: 80)
            .frame(maxWidth: .infinity)
            .background(.yellow)
    }
}

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)
    }
}