title: Custom component undefined in React Native
body: <p>I create a custom component called SimpleButton in a javascript file:</p>
  
  <pre><code>import React, {
    Text,
    View
  } from 'react-native';
  
  export default class SimpleButton extends React.Component{
    render(){
      return (
        &lt;View&gt;
          &lt;Text&gt;Simple Button&lt;/Text&gt;
        &lt;/View&gt;
      );
    }
  }
  </code></pre>
  
  <p>Then I import it to index javascript file:</p>
  
  <pre><code>    /**
   * Sample React Native App
   * https://github.com/facebook/react-native
   * @flow
   */
  
  import React, {
    AppRegistry,
    StyleSheet,
    View
  } from 'react-native';
  
  import SimpleButton from './App/Components/SimpleButton';
  
  class ReactNotes extends React.Component {
    render() {
      return (
        &lt;View style={styles.container}&gt;
          &lt;SimpleButton/&gt;
        &lt;/View&gt;
      );
    }
  }
  
  const styles = StyleSheet.create({
    container: {
      flex: 1,
      justifyContent: 'center',
      alignItems: 'center',
      backgroundColor: '#F5FCFF',
    }
  });
  
  AppRegistry.registerComponent('ReactNotes', () =&gt; ReactNotes);
  </code></pre>
  
  <p>Finally, run it on a Android device, it throws " <strong><em>Super expression must either be null or a function, not undefined</em></strong> " error. The error leads to SimpleButton class declaration code line ('export default class SimpleButton extends React.Component'.</p>
  
  <p>I currently use the latest version of React Native. I've searched some solutions but not works. Please help me!</p>