I want to determine the height of the content inside my (vertical) ScrollView.
ScrollView {
//My Content
}
Is this possible? I've tried a few things but nothing seems to work.
Unfortunately, using simply the GeometryReader isn't working, since it returns a value of 10 no matter what content is inside the ScrollView
Thanks!
The solution would be to have GeometryReader inside a .background/.overlay modifier. This makes it possible to read the height of the ScrollView content.
struct ContentView: View {
var body: some View {
ScrollView {
ForEach(0..<1000) { i in
Text("\(i)")
}
.background(
GeometryReader { proxy in
Color.clear.onAppear { print(proxy.size.height) }
}
)
}
}
}
We get an output of 20500.0 which is correct.
onAppear to onChange and pass it the state that is dynamic, E.g. Color.clear.onChange(of: chatData.messages) { print(proxy.size.height) }
I found another solution to this. You can use a PreferenceKey to propagate the size of the child view up to the parent. Check out this amazing article that goes over how to do this: https://zalogatomek.medium.com/swiftui-missing-intrinsic-content-size-how-to-get-it-6eca8178a71f
It's very similar to your solution with the clear color + GeometryReader, but obfuscates it into a nice view modifier, and sends the @State to the parent view.
struct ContentView: View {
@State var textSize: CGSize = .zero
var body: some View {
ScrollView {
Text("Hi, I'm a text")
.readIntrinsicContentSize(to: $textSize)
.background(Color.red)
Text("Size of above is: \(textSize.width) x \(textSize.height)")
.background(Color.blue)
}
}
}
extension View {
func readIntrinsicContentSize(to size: Binding<CGSize>) -> some View {
background(GeometryReader { proxy in
Color.clear.preference(
key: IntrinsicContentSizePreferenceKey.self,
value: proxy.size
)
})
.onPreferenceChange(IntrinsicContentSizePreferenceKey.self) {
size.wrappedValue = $0
}
}
}
struct IntrinsicContentSizePreferenceKey: PreferenceKey {
static let defaultValue: CGSize = .zero
static func reduce(value: inout CGSize, nextValue: () -> CGSize) {
value = nextValue()
}
}
I was working on pagination and needed a few values from the ScrollView. I came across this question, which contains an answer, but it also includes a few other bonus tips. Keep in mind that this is available on iOS 18.0 and above.
Hopefully someone could use this as a foundation and make it better:
ScrollView {
// Your content
}
.onScrollGeometryChange(for: [Double].self, of: { geometry in
[
geometry.contentSize.height,
geometry.contentOffset.y,
geometry.bounds.height
]
}, action: { _, newValue in
let contentHeight = newValue[0]
let offsetY = newValue[1]
let scrollViewHeight = newValue[2]
// print(contentHeight, offsetY, scrollViewHeight)
// print(vm.currentOffset)
if offsetY > contentHeight - scrollViewHeight {
// method for pagination
}
})
ScrollViewas well.