text: import * as React from 'react'
  import {Text, View, StyleSheet, Button, TouchableOpacity} from 'react-native';
  import ScanScreen from './screens/ScanScreen';
  import {createAppContainer} from 'react-navigation';
  import {createBottomTabNavigator} from 'react-navigation-tabs';
  
  export default class App extends React.Component {
    render() {
      return (
        <AppContainer/>
      );
    }
  }
  
  const TabNavigator = createBottomTabNavigator({
    Scan: {
      screen: ScanScreen
    }
  })
  
  const AppContainer = createAppContainer(TabNavigator);