Make sheet the exact size of the content inside - swift

Question

Let's say I have a custom view inside of a sheet, something like this
VStack {
Text("Title")
Text("Some very long text ...")
}
.padding()
.presentationDetents([.height(250)])
How can I get the exact height of the VStack and pass it to the presentationDetents modifier so that the height of the sheet is exactly the height of the content inside?

Answer 1

You can use a GeometryReader and PreferenceKey to read the size and then write it to a state variable. In my example, I store the entire size, but you could adjust it to store just the height, since it's likely that that is the only parameter you need.
struct ContentView: View {
#State private var showSheet = false
#State private var size: CGSize = .zero
var body: some View {
Button("View sheet") {
showSheet = true
}
.sheet(isPresented: $showSheet) {
VStack {
Text("Title")
Text("Some very long text ...")
}
.padding()
.background(
GeometryReader { geometryProxy in
Color.clear
.preference(key: SizePreferenceKey.self, value: geometryProxy.size)
}
)
.onPreferenceChange(SizePreferenceKey.self) { newSize in
size.height = newSize.height
}
.presentationDetents([.height(size.height)])
}
}
}
struct SizePreferenceKey: PreferenceKey {
static var defaultValue: CGSize = .zero
static func reduce(value: inout CGSize, nextValue: () -> CGSize) { value = nextValue() }
}

Answer 2

Using the general idea made by #jnpdx including some updates such as reading the size of the overlay instead of the background, here is what works for me:
struct ContentView: View {
#State private var showSheet = false
#State private var sheetHeight: CGFloat = .zero
var body: some View {
Button("Open sheet") {
showSheet = true
}
.sheet(isPresented: $showSheet) {
VStack {
Text("Title")
Text("Some very long text ...")
}
.padding()
.overlay {
GeometryReader { geometry in
Color.clear.preference(key: InnerHeightPreferenceKey.self, value: geometry.size.height)
}
}
.onPreferenceChange(InnerHeightPreferenceKey.self) { newHeight in
sheetHeight = newHeight
}
.presentationDetents([.height(sheetHeight)])
}
}
}
struct InnerHeightPreferenceKey: PreferenceKey {
static var defaultValue: CGFloat = .zero
static func reduce(value: inout CGFloat, nextValue: () -> CGFloat) {
value = nextValue()
}
}

Answer 3

More reuseable
struct InnerHeightPreferenceKey: PreferenceKey {
static var defaultValue: CGFloat = .zero
static func reduce(value: inout CGFloat, nextValue: () -> CGFloat) { value = nextValue() }
}
extension View {
func fixedInnerHeight(_ sheetHeight: Binding<CGFloat>) -> some View {
padding()
.background {
GeometryReader { proxy in
Color.clear.preference(key: InnerHeightPreferenceKey.self, value: proxy.size.height)
}
}
.onPreferenceChange(InnerHeightPreferenceKey.self) { newHeight in sheetHeight.wrappedValue = newHeight }
.presentationDetents([.height(sheetHeight.wrappedValue)])
}
}
struct ExampleView: View {
#State private var showSheet = false
#State private var sheetHeight: CGFloat = .zero
var body: some View {
Button("Open sheet") {
showSheet = true
}
.sheet(isPresented: $showSheet) {
VStack {
Text("Title")
Text("Some very long text ...")
}
.fixedInnerHeight($sheetHeight)
}
}
}

Answer 4

struct ContentView: View {
#State private var showingSheet = false
let heights = stride(from: 0.1, through: 1.0, by: 0.1).map { PresentationDetent.fraction($0) }
var body: some View {
Button("Show Sheet") {
showingSheet.toggle()
}
.sheet(isPresented: $showingSheet) {
Text("Random text ")
.presentationDetents(Set(heights))
}
}
}