Positioning Views with GeometryReader in SwiftUI

Question

I have a set of child views (GridView1 and GridView2) within a scrollview. The child views are within a VStack since I need them one below the other. I have a GeometryReader wrapping the child views and each of the child views have a GeometryReader inside them. I need the GeometryReader inside the child view to determine the width of the column spacing I need in a LazyVGrid.

The problem is that, using a GeometryReader inside the Child views causes the two child views stack on top of each other. I have tried to set the frame size of the child view but that limits the vertical scrolling and is not giving me the right result.

I would appreciate any help in resolving this problem.

ContentView:

struct ContentView: View {
    var body: some View {
        GeometryReader { geo in
            ScrollView {
                VStack(spacing: 20) {
                    GridView1()
                    GridView2()
                }//.frame(minHeight: 0, maxHeight: .infinity)
            }
        }
        .padding()
    }
}

GridView1:

struct GridView1: View {
    var body: some View {
        GeometryReader { g in
            let maxwidth = g.size.width/6 > 100 ? g.size.width/6 : 100
            let columns = Array(repeating: GridItem(.flexible(minimum: 100, maximum: maxwidth), spacing: 0), count: 6)
            
            ScrollView(.horizontal) {
                LazyVGrid(columns: columns, alignment: .leading, spacing: 10, pinnedViews: [.sectionHeaders]) {
                    Section(header: Text("Grid 1").font(.title)) {
                        ForEach(0...200, id:\.self) { index in
                            Text("\(index)").frame(maxWidth: .infinity)
                        }
                    }
                }
            }
            .background(Color.blue)
        }
    }
}

GridView2 (GridView1 and GridView2 are essentially the same thing)

struct GridView2: View {
    var body: some View {
        GeometryReader { g in
            let maxwidth = g.size.width/10 > 100 ? g.size.width/10 : 100
            let columns = Array(repeating: GridItem(.flexible(minimum: 100, maximum: maxwidth), spacing: 0), count: 10)
            ScrollView(.horizontal) {
                LazyVGrid(columns: columns, alignment: .leading, spacing: 20, pinnedViews: [.sectionHeaders]) {
                    Section(header: Text("Grid 2").font(.title)) {
                        ForEach(1000...1200, id:\.self) { index in
                            ZStack {
                                Text("\(index)")
                            }
                            .frame(maxWidth: .infinity)
                            .background(Color.green)
                        }
                    }//.frame(minHeight: 0, maxHeight: .infinity)
                }
            }//.frame(minHeight: 1000, maxHeight: .infinity)
            //.frame(maxWidth: .infinity, maxHeight: .infinity)
            //.background(Color.red)
        }
    }
}

here is what I am expecting:

Here is what I am currently getting. As you can see below, the child views are bunching up at the top.

Asperi · Accepted Answer · 2020-11-13 05:10:22Z

Instead of use internal GeometryReader that confuses external ScrollView, pass width from top GeometryReader into sub-views grids.

Here is worked solution. Tested with Xcode 12.1 / iOS 14.1

struct ContentView: View {
    var body: some View {
        GeometryReader { geo in
            ScrollView {
                VStack(spacing: 20) {
                    GridView1(width: geo.size.width)
                    GridView2(width: geo.size.width)
                }
            }
        }
        .padding()
    }
}

struct GridView1: View {
    let width: CGFloat
    var body: some View {
        let maxwidth = width/6 > 100 ? width/6 : 100
        let columns = Array(repeating: GridItem(.flexible(minimum: 100, maximum: maxwidth), spacing: 0), count: 6)
        
        ScrollView(.horizontal) {
            LazyVGrid(columns: columns, alignment: .leading, spacing: 10, pinnedViews: [.sectionHeaders]) {
                Section(header: Text("Grid 1").font(.title)) {
                    ForEach(0...200, id:\.self) { index in
                        Text("\(index)").frame(maxWidth: .infinity)
                    }
                }
            }
        }
        .background(Color.blue)
    }
}

struct GridView2: View {
    let width: CGFloat
    var body: some View {
        let maxwidth = width/10 > 100 ? width/10 : 100
        let columns = Array(repeating: GridItem(.flexible(minimum: 100, maximum: maxwidth), spacing: 0), count: 10)
        ScrollView(.horizontal) {
            LazyVGrid(columns: columns, alignment: .leading, spacing: 20, pinnedViews: [.sectionHeaders]) {
                Section(header: Text("Grid 2").font(.title)) {
                    ForEach(1000...1200, id:\.self) { index in
                        ZStack {
                            Text("\(index)")
                        }
                        .frame(maxWidth: .infinity)
                        .background(Color.green)
                    }
                }
            }
        }
    }
}

this works! Thank you. However, I am wondering what is the right way to use the GeometryReader because this limits the use of GeometryReader in downstream views. Any pointers or examples you can point me to. Thanks!

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