Add toggle navBar to example-redux

example-redux/src/screens/FirstTabScreen.js

 import { connect } from 'react-redux';
 import * as counterActions from '../reducers/counter/actions';
 
+let navBarVisiable = true;
+
 // this is a traditional React component connected to the redux store
 class FirstTabScreen extends Component {
   static navigatorStyle = {
           <Text style={styles.button}>Modal Screen</Text>
         </TouchableOpacity>
 
+        <TouchableOpacity onPress={ this.onToggleNavBarPress.bind(this) }>
+          <Text style={styles.button}>Toggle NavBar</Text>
+        </TouchableOpacity>
+
         <Text style={{fontWeight: '500'}}>String prop: {this.props.str}</Text>
         <Text style={{fontWeight: '500'}}>Number prop: {this.props.num}</Text>
         <Text style={{fontWeight: '500'}}>Object prop: {this.props.obj.str}</Text>
       }
     });
   }
+
+  onToggleNavBarPress() {
+    navBarVisiable = !navBarVisiable;
+    this.props.navigator.toggleNavBar({
+      to: navBarVisiable ? 'shown' : 'hidden',
+      animated: true
+    });
+  }
 }
 
 const styles = StyleSheet.create({