Using GeometryReader with ScrollView - swiftui

Question

I'm trying to use GeometryReader to assign a maxHeight to a list in a Scrollview.
For the purpose of this question, I created the following project : GeometryReaderTesting.
It sets up a ContentView with a :
- Text.
- List.
- Text.
I extracted the List and last Text into their own view, using #ViewBuilder and I want to set the maxHeight of the List to .5 the height of my user's screen.
The problem is that the app won't build with the following errors, and the GeometryReader doesn't seem to be computing the correct height:
Here is my ContentView code, if anyone has an idea of what I'm doing wrong...
struct ContentView: View {
let arrayWithStuff = [ "one","two","three","four","five","six","seven","eight","nine","ten", "eleven", "twelve"]
var heightOfView: CGFloat = 0.0 // To be set by GeometryReader
var body: some View {
let myString = "Top of Test App"
return ZStack {
GeometryReader { g in
heightOfView = g.size.height
NavigationView {
print("height of view : \(heightOfView)")
ScrollView {
VStack {
Text(myString)
.padding()
Divider()
self.ViewBody()
} // END of Vstack
.navigationBarTitle("Test App", displayMode: .inline)
} // END of Scrollview
}//End of NavigationView
} // End of Geometry reader
} // End of Zstack
} // End of body
#ViewBuilder func ViewBody() -> some View {
VStack {
List {
ForEach (self.arrayWithStuff, id: \.self) { item in
Text(item) }
} // END of List
.frame(maxHeight: heightOfView*0.5)
Divider()
Text("Bottom of TEST APP")
}
.padding()
}
}
Again, any help would be appreciated.

Answer 1

Here is a demo of possible solution. Tested with Xcode 11.4.
struct ContentView: View {
let arrayWithStuff = [ "one","two","three","four","five","six","seven","eight","nine","ten", "eleven", "twelve"]
var body: some View {
let myString = "Top of Test App"
return ZStack {
GeometryReader { g in
NavigationView {
ScrollView {
VStack {
Text(myString)
.padding()
Divider()
self.ViewBody(height: g.size.height)
} // END of Vstack
.navigationBarTitle("Test App", displayMode: .inline)
} // END of Scrollview
}//End of NavigationView
} // End of Geometry reader
} // End of Zstack
} // End of body
func ViewBody(height: CGFloat) -> some View {
print("height of view : \(height)")
return VStack {
List {
ForEach (self.arrayWithStuff, id: \.self) { item in
Text(item) }
} // END of List
.frame(height: height*0.5)
Divider()
Text("Bottom of TEST APP")
}
.padding()
}
}