title: onPress function doesn't work
body: <p>I would like to add multiple function on onPress. So I have onPress function like this. But that doesn't work. </p>
  
  <pre><code>  navigateToScreen = (route) =&gt; () =&gt; {
        const navigateAction = NavigationActions.navigate({
          routeName: route
        });
        this.props.navigation.dispatch(navigateAction);
      }
  
      onButtonPress() {
        this.navigateToScreen('Home', { isStatusBarHidden: false })
      }
  
      render() {
        return (
          &lt;View style={styles.container}&gt;
            &lt;TouchableOpacity
              style={styles.menuItem}
              onPress={() =&gt; {this.onButtonPress.bind(this)}
            &gt;
    ...
  </code></pre>
  
  <p><code>navigateToScreen</code> does't work, let me know why.</p>