title: How to implement both DrawerNavigator and StackNavigator
body: <p>I am developing an app using react-native-navigation and I want to have a StackNavigator and a DrawerNavigator in the project. So, I have implemented them in the app.js but the apps crashes giving this error "The development server returned response error with code: 500".I have implemented them separetly and it works but I couldn't implement them together.Any suggestion?</p>
  
  <p>this is my code for app.js</p>
  
  <pre><code>import React, {
      Component
  } from 'react';
  
  import {
      StyleSheet,
      Text,
      View
  } from 'react-native';
  
  import {
      createStackNavigator,
      DrawerNavigator,
      DrawerItems
  } from "react-navigation";
  
  import {
      Container,
      Header,
      Content,
      Thumbnail,
      Button,
      Body
  } from 'native-base';
  
  import Profile from './components/Profile.js';
  import Main from './components/Main.js';
  import Login from './components/Login.js';
  import Product from './components/Product.js';
  
  export default class App extends Component {
      render() {
          return ( 
             &lt;Navapp /&gt;
          );
      }
  }
  
  const styles = StyleSheet.create({
      // styles here
  });
  
  export const Drawer = DrawerNavigator({
      Main: {
          screen: Main
      },
      Profile: {
          screen: Profile
      },
  }, {
  initialRouteName: 'Main',
  contentComponent: CustomDrawer,
  drawerPosition: 'Left',
  drawerOpenRoute: 'DrawerOpen',
  drawerCloseRoute: 'DrawerClose',
  drawerToggleRoute: 'DrawerToggle',
  });
  
  export const CustomDrawer = (props) =&gt; ( 
      &lt;Container&gt;
          &lt;Header style = {
              styles.headerStyle
          }&gt;
              &lt;Body style = {
                  styles.bodyStyle
              }&gt;
                  &lt;Thumbnail style = {
                      {
                          height: 100,
                          width: 100
                      }
                  }
                  source = {
                      require('../image/logo.png')
                  }/&gt; 
              &lt;/Body&gt; 
          &lt;/Header&gt;
          &lt;Content&gt;
              &lt;DrawerItems { ...props}  /&gt; 
          &lt;/Content &gt; 
      &lt;/Container&gt;
  )
  
  export const Navapp = createStackNavigator({
      Login: {
          screen: Login
      },
      Drawer: {
          screen: Drawer
      },
      Product: {
          screen: Product
      },
  });
  </code></pre>