Crash when attempting to scroll using ScrollViewReader in a SwiftUI List-CodePudding

I am trying to scroll to a newly appended view in a SwiftUI List using ScrollViewReader but keep crashing with EXC_BAD_INSTRUCTION in scrollTo(_:) after adding a few items. I am using Xcode 14.0.1 and iOS 16.0 simulator.

Here is a minimal demo that exhibits the issue:

struct ContentView: View {

    @State var items = [Item]()
    @State var scrollItem: UUID? = nil
    
    var body: some View {
        NavigationView {
            ScrollViewReader { proxy in
                List {
                    ForEach(items) { item in
                        Text(item.id.uuidString)
                            .id(item.id)
                    }
                }
                .listStyle(.inset)
                .onChange(of: scrollItem) { newValue in
                    proxy.scrollTo(newValue)
                }
            }
            .navigationTitle("List Demo")
            .toolbar {
                Button("Add") {
                    addItem()
                }
            }
        }
    }

    func addItem() {
        items.append(Item())
        scrollItem = items.last?.id
    }
}

struct Item: Identifiable {
    let id = UUID()
}

I can get past the issue using a ScrollView instead of a List, but I would like to use the native swipe-to-delete functionality in the real project.

CodePudding user response：

List is not supported well in ScrollViewReader. See this thread.

This solution is ugly, but works. The bad thing is that list blinks when you add a new item. I used one of the ideas from the thread above.

import SwiftUI

struct ContentView: View {

    @State var items = [Item]()
    @State var scrollItem: UUID? = nil
    @State var isHidingList = false

    var body: some View {
        NavigationView {
            VStack(alignment: .leading) {
                if isHidingList {
                    list.hidden()
                } else {
                    list
                }
            }
            .onChange(of: scrollItem) { _ in
                DispatchQueue.main.async {
                    self.isHidingList = false
                }
            }
            .navigationTitle("List Demo")
            .toolbar {
                Button("Add") {
                    addItem()
                }
            }
        }
    }

    var list: some View {
        ScrollViewReader { proxy in
            List {
                ForEach(items) { item in
                    Text(item.id.uuidString)
                        .id(item.id)
                }
            }
            .listStyle(.inset)
            .onChange(of: scrollItem) { newValue in
                guard !isHidingList else { return }
                proxy.scrollTo(newValue)
            }
            .onAppear() {
                guard !isHidingList else { return }
                proxy.scrollTo(scrollItem)
            }
        }
    }

    func addItem() {
        isHidingList = true
        items.append(Item())
        scrollItem = items.last?.id
    }

}

struct Item: Identifiable {
    let id = UUID()
}