SwiftUI TabbedView only shows first tab's content

Try adding tags:

    TabbedView {
        Text("Hello world")
            .tabItem { Text("Hello") }
            .tag(0)
        Text("Foo bar")
            .tabItem { Text("Foo") }
            .tag(1)
    }

I was able to fix this by adding a selection state variable and passing that in for the selection:

struct ContentView : View {
    @State private var selection = 1

    var body: some View {
        TabbedView(selection: $selection) {
            Text("Tab 1!").tabItemLabel(
                Text("Tab 1")).tag(1)
            Text("Tab 2!").tabItemLabel(Text("Tab 2")).tag(2)
        }
    }
}

Now, tapping "Tab 2" will show "Tab 2!" on the screen, as opposed to a blank screen.

This was using Xcode 11.0 beta 2 (11M337n), macOS Catalina 10.15 Beta (19A487l).