App.js

/**
 * Sample React Native App
 * https://github.com/facebook/react-native
 * @flow
 */

import React, { Component } from 'react';
import {
  StyleSheet,
  Text,
  View
} from 'react-native';


import HomeScreen from './ui/HomeScreen';
import LoginScreen from './ui/LoginScreen.js';
import { StackNavigator } from 'react-navigation'; 

export default class App extends Component{
  render() {
    return <RootStack />;
  }
}
const RootStack = StackNavigator(
  {
    Home: {
      screen: HomeScreen,
    },
    Login: {
      screen: LoginScreen,
    },
  },
  {
    initialRouteName: 'Home',
    navigationOptions: {
      headerStyle: {
        backgroundColor: '#f4511e',
      },
      headerTintColor: '#fff',
      headerTitleStyle: {
        fontWeight: 'bold',
      },
    },
  }
);
const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
    backgroundColor: '#F5FCFF',
  },
  welcome: {
    fontSize: 20,
    textAlign: 'center',
    margin: 10,
  },
  instructions: {
    textAlign: 'center',
    color: '#333333',
    marginBottom: 5,
  },
});