反应导航栏不显示

Question

我是React-native的新手，我正在尝试为我的应用创建场景。我遇到两件事情有困难：首先，我无法理解为什么带标题的导航栏没有显示。我正在使用React Navigation。其次，我不知道我开始开发应用程序的方式是否正确。

Index.js

import { AppRegistry } from 'react-native';
import App from './App';

AppRegistry.registerComponent('Hola', () => App);

App.js

import React, { Component } from 'react';
import {
    View,
} from 'react-native';
import Hola from './src/ConversationListScreen';
import styles from './src/styles';

export default class App extends Component<{}> {
  render() {
    return (
        <View>
          <Hola/>
        </View>
    );
  }
}

的src / ConversationListScreen.js

import React, { Component } from 'react';
import { StackNavigator } from 'react-navigation';
import {
    AppRegistry,
    Text,
    View,
} from 'react-native';

export default class ConversationListScreen extends Component
{
    static navigationOptions = {
        title: 'Hola',
    };
    render() {
        return <Text>Hello, Navigation</Text>;
    }
}

export const Hola = StackNavigator({
    ConversationList: { screen: ConversationListScreen },
});

AppRegistry.registerComponent('ConversationListScreen', () => Hola);