.sheet修改器更改ListView上的背景颜色

Question

不确定我是在做错什么还是错误。我正在运行Xcode 12.1和iOS 14.1。这不是在Xcode 11上发生的。

代码如下：

enum SheetView: Identifiable {
    var id: SheetView { self }
    case add
}

struct ContentView: View {
    var items = ["Book", "Cat", "Dog"]
    @State private var sheetView: SheetView?

    var body: some View {
        NavigationView {
            List {
                ForEach(items, id: \.self) { item in
                    Text(item)
                }
            }
            .navigationTitle("Items")
            .toolbar {
                ToolbarItem(placement: .primaryAction) {
                    Button(action: {
                        sheetView = .add
                    }, label: {
                        Text("Add")
                    })
                }
            }
            .sheet(item: $sheetView, onDismiss: { sheetView = nil }) { sheet in
                if sheet == .add {
                    Text("Add")
                }
            }
        }
    }
}