a dynamic sheet demo

dynamicHeightSheet.swift

import SwiftUI

struct ContentView: View {
  @State var show = false
  @State var height: CGFloat = 250
  var body: some View {
    List {
      Button("Pop Sheet") {
        height = 250
        show.toggle()
      }
      Button("Pop ScrollView Sheet") {
        height = 1000
        show.toggle()
      }
    }
    .adaptiveSheet(isPresent: $show) {
      ViewThatFits(in: .vertical) {
        SheetView(height: height)
        ScrollView {
          SheetView(height: height)
        }
      }
    }
  }
}

struct SheetView: View {
  let height: CGFloat
  var body: some View {
    Text("Hi")
      .frame(maxWidth: .infinity, minHeight: height)
      .presentationBackground(.orange)
  }
}

extension View {
  func adaptiveSheet<Content: View>(isPresent: Binding<Bool>, @ViewBuilder sheetContent: () -> Content) -> some View {
    modifier(AdaptiveSheetModifier(isPresented: isPresent, sheetContent))
  }
}

struct AdaptiveSheetModifier<SheetContent: View>: ViewModifier {
  @Binding var isPresented: Bool
  @State private var subHeight: CGFloat = 0
  var sheetContent: SheetContent

  init(isPresented: Binding<Bool>, @ViewBuilder _ content: () -> SheetContent) {
    _isPresented = isPresented
    sheetContent = content()
  }

  func body(content: Content) -> some View {
    content
      .background(
        sheetContent // 在此获取尺寸，防止初次弹出抖动
          .background(
            GeometryReader { proxy in
              Color.clear
                .task(id: proxy.size.height) {
                  subHeight = proxy.size.height
                }
            }
          )
          .hidden()
      )
      .sheet(isPresented: $isPresented) {
        sheetContent
          .presentationDetents([.height(subHeight)])
      }
      .id(subHeight)
  }
}

Okay thank you @fatbobman. I understand.

This is my scenario, I have some view constrained in height that needs to present a sheet.
Now after your feedback: views that do no use a scrollview works fine, but yes scrollview does not work.

Do you think you have a solution for using a scrollview in a sheet presented in a height constrained view?

Thank you again, and totally fine if this is too time consuming, I will find another way. Thank you.

struct MainView: View {
    var body: some View {
        VStack {
            ChildView()
                .frame(maxWidth: .infinity, maxHeight: 400)
        }
    }
}

struct ChildView: View {
    var body: some View {
        VStack {
            Text("Text")
                .frame(maxWidth: .infinity, maxHeight: 400)
        }
        .adaptiveSheet(isPresented: .constant(true)) {
            SheetView()
        }
    }
}

struct SheetView: View {
    var body: some View {
       // VStack works fine, ScrollView does not work 
        VStack {
        // ScrollView {
            Rectangle()
                .frame(width: 200, height: 200)
                .padding(10)
                .foregroundStyle(.blue)
            
            Rectangle()
                .frame(width: 200, height: 200)
                .padding(10)
                .foregroundStyle(.blue)
            
            Rectangle()
                .frame(width: 200, height: 200)
                .padding(10)
                .foregroundStyle(.blue)
        }
        .frame(maxWidth: .infinity, maxHeight: .infinity)
    }
}