RootTabNavigator

  LoggedOut_StackNavigator

    ...

  LoggedIn_StackNavigator

    LoggedIn_TabNavigator <-- TabBar rendered by this Navigator

      TabA_StackNavigator

        ScreenA
        ScreenB

{
  "action": Object {
    "params": Object {},
    "routeName": "ScreenB",
    "type": "Navigation/NAVIGATE",
  },
  "params": Object {},
  "routeName": "AllScreens_StackNavigator",
  "type": "Navigation/NAVIGATE",
}