Show Login screen first

example-redux/src/app.js

       case 'login':
         Navigation.startSingleScreenApp({
           screen: {
-            screen: 'example.FirstTabScreen',
+            screen: 'example.LoginScreen',
             title: 'Login',
             navigatorStyle: {}
           },

example-redux/src/screens/PushedScreen.js

   ScrollView,
   TouchableOpacity,
   StyleSheet,
-  TextInput
+  TextInput,
+  Alert
 } from 'react-native';
 import {connect} from 'react-redux';
 import * as counterActions from '../reducers/counter/actions';
     super(props);
     this.bgColor = this.getRandomColor();
     console.log(`constructor ${this.bgColor}`);
+    this.props.navigator.setOnNavigatorEvent(this.onNavigatorEvent.bind(this));
     this.currentBackButton = 0;
   }
 
     return color;
   }
 
+  onNavigatorEvent(event) {
+    console.log('onNavigatorEvent ' + event.id);
+    switch (event.id) {
+      case 'cancel':
+        Alert.alert('NavBar', 'Cancel button pressed');
+        break;
+
+      case 'accept':
+        Alert.alert('NavBar', 'Accept button pressed');
+        break;
+    }
+  }
+
   render() {
     return (
       <View style={{flex: 1, padding: 20, backgroundColor: this.bgColor}}>