title: react native flatlist not rendering
body: <p>I've been experimenting with react native and I cannot get my <code>FlatList</code> to render correctly. Here is the component. If it matters, I am using <code>react-navigation</code> to render this component.</p>
  
  <pre><code>class FactoryScreen extends React.Component {
    static navigationOptions = {
      title: 'test test',
    };
  
    constructor(props) {
      super(props);
  
      this.state = {
        datasource: [
          {
            id: 21, machine_key: 'f', clamp_id: 'c0',
          },
          {
            id: 22, machine_key: 'f', clamp_id: 'c1',
          },
          {
            id: 23, machine_key: 'f', clamp_id: 'c2',
          },
        ]
      };
    }
  
    render() {
      const { goBack } = this.props.navigation;
      return (
        &lt;List style={{flex: 1}}&gt;
          &lt;FlatList
            data={this.state.datasource}
            renderItem={({item}) =&gt; {
              console.log(item);
              return (&lt;ListItem title={`${item.clamp_id} clamp`} /&gt;);
            }}
          /&gt;
        &lt;/List&gt;
      );
    }
  }
  </code></pre>
  
  <p>I can see my <code>item</code> object get logged to the console but I can't get it to render for whatever reason. Any thoughts as to what I am doing wrong?</p>