//stack.js

    const AppNavigator = createStackNavigator(
      {
        DetailPage: DetailPage, //Screen A
        MainScreen: { .        //Screen B
        screen: MainScreen,
        navigationOptions: {
        header: null
      }
    }
{
    initialRouteName: "MainScreen"
  }
}


//MainScreen.js

      <View style={{ flex: 1 }}>
          <TabScreen />
        </View>

//TabScreen.js

const TabScreen = createMaterialTopTabNavigator(
  {
    Home: { screen: HomeStack },
    // Videos: { screen: Videos },
    Videos: { screen: Videos },
    Shows: { screen: AllShows },
    Live: { screen: Live }
  }
)'

import React, { Component } from "react";
import { View, Text } from "react-native";
import { createStackNavigator, createAppContainer } from "react-navigation";
import { createMaterialBottomTabNavigator } from "react-navigation-material-bottom-tabs";

import Camera from "./screens/camera";
import Welcome from "./screens/welcome";

import Scanner from "./screens/scanner";
import Cards from ".//screens/cards";

const BottomNavigation = createMaterialBottomTabNavigator(
  {
    Scan: { screen: Scanner },
    Cards: { screen: Cards },
    Settings: { screen: Cards }
  },
  {
    initialRouteName: "Scan",
    shifting: true
  }
);
const AppNavigator = createStackNavigator({
  Welcome: {
    screen: Welcome,
    navigationOptions: { header: null }
  },
  Camera: {
    screen: Camera,
    navigationOptions: { header: null }
  },
  Home: {
    screen: BottomNavigation,
    navigationOptions: { header: null }
  }
});

export default createAppContainer(AppNavigator);