ScrollView

解决方法是将所有视图放入ZStack，并在滚动视图中添加一些假视图.

import Introspect

struct ContentView: View {

@StateObject private var myCoord = MyCoord()

var body: some View {
    let sizeOfPlaceholder = myCoord.maxSize - myCoord.minSize
    
    ZStack(alignment: .top) {
        VStack(spacing: 0) {
            Color.black
                .frame(height: myCoord.minSize)
            
            ScrollView {
                Color.brown
                    .frame(height:sizeOfPlaceholder)
                
                ForEach(0..<20) { number in
                    Text("\(number)")
                        .background(Color.red)
                        .frame(height: 20)
                }
            }
            .padding(.vertical, 1)
            .introspectScrollView { scroll in
                scroll.delegate = myCoord
            }
        }
        
        Color.green
            .frame(height: myCoord.height)
    }
    
   }
}

class MyCoord: NSObject, UIScrollViewDelegate, ObservableObject {

let maxSize: CGFloat = 76
let minSize: CGFloat = 56

@Published var height: CGFloat =  76

func scrollViewDidScroll(_ scrollView: UIScrollView) {
    print(scrollView.contentOffset.y)
    let size = maxSize - scrollView.contentOffset.y
    height = min(maxSize, max(minSize, size))
}
}