Navigator.ts

// ... screen imports
import { Platform } from "react-native";
import {
  createBottomTabNavigator,
  createDrawerNavigator,
  createStackNavigator,
  createSwitchNavigator
} from "react-navigation";

const HomeStack = createStackNavigator({ DetailScreen, HomeScreen, OptionsScreen });

const MainNavigator = Platform.select({
  ios: createBottomTabNavigator({ HomeStack, SettingsScreen }),
  android: createDrawerNavigator({ HomeStack, SettingsScreen })
});

const RootSwitch = createSwitchNavigator(
  { LoadingScreen, MainNavigator },
  { initialRouteName: "MainNavigator" }
);