ios - SwiftUI List doesn't use lazy loading for first 20 elements. How to fix that?

Question

We have the following row view. The screen has space to render about 4 rows.

struct SampleRow: View {
    let id: Int

    var body: some View {
        Text("Row (id)").frame(height: 200)
    }

    init(id: Int) {
        print("Loading row (id)")
        self.id = id
    }
}

Use LazyVStack to make a list

struct ContentView: View {
    var body: some View {
        ScrollView {
            LazyVStack {
                ForEach(1...1000, id: .self, content: SampleRow.init)
            }
        }
    }
}

Result

Loading row 1
Loading row 2
Loading row 3
Loading row 4
Loading row 5

Use List to make a list

struct ContentView: View {
    var body: some View {
        List {
            ForEach(1...1000, id: .self, content: SampleRow.init)
        }
    }
}

Result

Loading row 1
Loading row 2
Loading row 3
Loading row 4
Loading row 5
Loading row 6
Loading row 7
Loading row 8
Loading row 9
Loading row 10
Loading row 11
Loading row 12
Loading row 13
Loading row 14
Loading row 15
Loading row 16
Loading row 17
Loading row 18
Loading row 19
Loading row 20

Even if I change the row height from 200 to 400 when the screen has space to render only 2 rows, List loads first 20 items in any case.

How to change this value?

question from:https://stackoverflow.com/questions/65869281/swiftui-list-doesnt-use-lazy-loading-for-first-20-elements-how-to-fix-that

Answer 1

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