Adding Navigation using React Navigation & Switch Navigator

In this part, we'll learn how to add navigation using React navigation and the switch navigator.

React Native doesn’t include builtin navigation support but you can use third-party packages provided by the community such as the react-navigation library.

This library comes also with iOS and Android gestures and animations for transitioning between screens.

After creating your components or screens, you can provide a route configuration using methods like createSwitchNavigator() which creates a switch navigation system. In the route configuration, you supply the route names as the keys and and the components to use for the routes via a screen property.

You can also specify the initial route in the navigation stack using the initialRouteName on the options object.

Head back to your terminal and run the following command from the root of your project to install react-navigation from npm:

$ npm install --save react-navigation

You also need to install the react-native-gesture-handler and react-native-reanimated libraries:

$ npm install --save react-native-gesture-handler react-native-reanimated

After that, you need to re-run your react-native run-android command if your app is already started.

Note: For iOS, it’s the react-native run-ios command.

Restructuring our project code

Before adding navigation, let’s first restructure our code. In the previous parts, we have added all components in one App.js file. This is file for small examples but when your project starts growing, you need to put reusable components and screens in their own files and even folders.

Let’s create two components and screens folders in the root of our project:

The components folder will contain the reusable components in our project,
The screens folder will contain the screens of our application.

Head back to your terminal, make sure your are in the root folder of your React Native project and run the following command to create the two folders:

$ mkdir components screens

Open the App.js file and let’s start with our first screen which is SplashScreen.

Inside the screens folder, create a SplashScreen.js file:

$ cd screens
$ touch SplashScreen.js

Open the SplashScreen.js file and add the following code:

import React from 'react';

import {
    View,
    Text,
    ImageBackground
  } from 'react-native';
import styles from '../styles';

const SplashScreen = () => {
    return (
        <View style={styles.container} >
            <ImageBackground style={styles.backgroundImage} source= style={styles.backgroundImage}>

                <View style={styles.logoContainer}>
                    <Text style={styles.logoText}>
                        Newzzz
          </Text>
                    <Text style={styles.logoDescription}>
                        Get your doze of daily news!
          </Text>

                </View>
            </ImageBackground>
        </View>
    );
}
export default SplashScreen;

Next, remove the code of the component from the App.js file and replace it with an import from the screens/SplashScreen.js file:

import SplashScreen from './screens/SplashScreen';

Next, in the components folder, create an IconButton.js file and add the following code:

import React from 'react';

import {
  View,
  Text,
  Image,
  TouchableHighlight,
} from 'react-native';
const IconButton = ({title, color, bgcolor, onPress, width, icon }) =>{
    return (
      <TouchableHighlight onPress = { onPress } style= { { flexDirection: 'row', alignItems: 'center', justifyContent: 'center', backgroundColor: bgcolor } }>

      <View style={ {width: width, flexDirection: 'row', justifyContent: 'center', alignItems: 'center' } }>
        <Image style = { { height: 27, width:27, margin : 5 } } source = {  icon }></Image>
        <Text style = { {color: color }} > { title } </Text>      
      </View>
      </TouchableHighlight>
    );
  }
export default IconButton;

Next, inside the components folder, add an ArticleItem.js file and add the following code:

import React from 'react';

import {
    View,
    Text,
    Image,
    Linking
  } from 'react-native';
import AsyncStorage from '@react-native-community/async-storage';
import bookmarkIcon from '../assets/bookmark.png';
import readIcon from '../assets/read.png';
import IconButton from './IconButton';
import styles from '../styles';

const saveArticle = async (key, value) =>{
    try {
      await AsyncStorage.setItem(key, value);
      getAllData();

    } catch (e) {
      console.log(e);
    }
  };

  const getAllData = () =>{
    AsyncStorage.getAllKeys().then((keys) => {
      return AsyncStorage.multiGet(keys)
        .then((result) => {
          console.log(result);
        }).catch((e) =>{
          console.log(e);
        });
    });
  }

  const openURL = (url) => {
    Linking.openURL(url).catch((err) => console.error('An error occurred', err));
  }



  const ArticleItem = ({article}) => {
    const { title, description, url, urlToImage } = article;

    return (
      <View style = { styles.articleContainer }>
        <Image style={ styles.articleImage } source={{ uri: urlToImage }} />
        <Text style= { styles.articleTitle }>
          { title }
        </Text>
        <Text style = { styles.articleDescription }>
          { description }
        </Text>

        <View style = { styles.articleBtns}>
        <IconButton width= "50%" color = "white" bgcolor = "#ff5c5c" icon = { readIcon } onPress = { () => { openURL(url)} } title = "Open" />
        <IconButton width= "50%" color = "white" bgcolor = "#ff5c5c" icon = { bookmarkIcon } onPress = { () => { saveArticle(title, url); } } title = "Read later" />
        </View>
      </View>
    )
  }
  export default ArticleItem;

Next, inside the components folder create a FlatListItemSeparator.js file and add the following code:

import React from 'react';

import {
    View
} from 'react-native';
const FlatListItemSeparator = () => {
    return (
        <View
            style={{
                height: 1,
                width: "100%",
                backgroundColor: "#000",
            }}
        />
    );
}
export default FlatListItemSeparator;

Make sure to remove the FlatListItemSeparator component from the App.js file

Next, create a FlatListHeader.js file and add the following code:

import React from 'react';

import {
    View,
    Text
} from 'react-native';
const FlatListHeader = () => {
    return (
        <View elevation={1}
            style={{
                height: 100,
                width: "97%",
                margin: 5,
                backgroundColor: "#fff",
                border: 2.9,
                borderColor: "black",
                alignSelf: "center",
                shadowColor: "#000",
                shadowOffset: {
                    width: 0,
                    height: 16,
                },
                shadowOpacity: 1,
                shadowRadius: 7.49
            }}
        >
            <Text style={{ textShadowColor: 'black', textShadowOffset: { width: 1, height: 3 }, textShadowRadius: 10, fontSize: 40, fontWeight: '800', flex: 1, alignSelf: "center", paddingTop: 30, fontSize: 40 }}>Latest articles</Text>
        </View>
    );
}
export default FlatListHeader;

Make sure to remove the FlatListHeader component from the App.js file.

Next, add a HomeScreen.js file inside the screens folder and add the following code:

import React from 'react';

import {
    View,
    FlatList
} from 'react-native';
import FlatListItemSeparator from '../components/FlatListItemSeparator';
import FlatListHeader from '../components/FlatListHeader';
import ArticleItem from '../components/ArticleItem';
const HomeScreen = (props) => {
    console.log("articles: ", props.articles);
    return (
        <View>
            <FlatList
                data={props.articles}
                ListHeaderComponent={FlatListHeader}
                ItemSeparatorComponent={FlatListItemSeparator}
                keyExtractor={(item, index) => index.toString()}
                renderItem={({ item }) => <ArticleItem article={item} />}
            />
        </View>
    );
}
export default HomeScreen;

Next, remove the code of the HomeScreen component from the App.js file and replace it with an import statement:

import HomeScreen from './screens/HomeScreen';

This is the code of the App.js file:

import React, { useState , useEffect } from 'react';
import SplashScreen from './screens/SplashScreen';
import HomeScreen from './screens/HomeScreen';

const App = () => {
  const API_KEY = "<YOUR_API_KEY>";
  const URL = `https://newsapi.org/v2/top-headlines?sources=techcrunch&apiKey=${API_KEY}`;
  const [articles, setArticles] = useState([]);
  const [loading, setLoading ] = useState(true);
  useEffect(()=>{
    fetch(URL)
    .then((response) => response.json())
    .then((responseJson) => {
      return responseJson.articles;
    })
    .then( articles  => {
      setArticles(articles);
      //console.log(articles);
      setLoading(false);
    })
    .catch( error => {
      console.error(error);
    });

  } , []);

  if (loading){
      return <SplashScreen />
    } else {
      return <HomeScreen articles = { articles }/>
  }
};
export default App;

We simply import SplashScreen and HomeScreen components from the screens folder and we use React conditional rendering to render them. We also use the useState and useEffect hooks to create state and fetch data.

Note: Make sure to replace <YOUR_API_KEY> with your own API key from the news API.

When data is still loading the loading state variable has a true value. After data is fetched, it will have a false value.

If loading is true, we tell React Native to render the SplashScreen component. Otherwise, it renders the HomeScreen component with the articles data, fetched from the news server using the Fetch API and the useEffect() hook, passed as a prop.

If your Android emulator is running, press double R in your keyboard to reload your app or run the following command to start the emulator with your app:

$ react-native run-android

If there is no error, congratulations, you have successfully restructured your code.

This is a screenshot of our project’s structure in Visual Studio Code:

React Native Example

Now, let’s replace conditional rendering with a real navigation system.

React Navigation using `createSwitchNavigator`

According to the docs:

The purpose of SwitchNavigator is to only ever show one screen at a time. By default, it does not handle back actions and it resets routes to their default state when you switch away. This is the exact behavior that we want from the authentication flow.

First, in your App.js file, add the following imports:

import { createSwitchNavigator, createAppContainer } from "react-navigation";

Next, create a switch navigator using the following code:

const AppNavigator = createSwitchNavigator({
  Splash: SplashScreen,
  Home: HomeScreen
});

We pass in a route configuration of tow routes:

The Splash route mapped to the SplashScreen component,
The Home route mapped to the HomeScreen component.

Next, create an application container using the following code:

AppContainer = createAppContainer(AppNavigator);

According to the docs:

Containers are responsible for managing your app state and linking your top-level navigator to the app environment. On Android, the app container uses the Linking API to handle the back button. The container can also be configured to persist your navigation state. On web, you'd use different containers than React Native.

Next, call the app container component from your App function as follows:

const App = () => {
  return <AppContainer />
};

Next, we’ll add the code for fetching data (which was previously in the App() function) to SplashScreen.

First, import the useEffect() hook:

import { useEffect } from 'react';

Next, change SplashScreen as follows:

const SplashScreen = (props) => {
    const API_KEY = "<YOUR_API_KEY_HERE>";
    const URL = `https://newsapi.org/v2/top-headlines?sources=techcrunch&apiKey=${API_KEY}`;

    useEffect(()=>{
      fetch(URL)
      .then((response) => response.json())
      .then((responseJson) => {
        return responseJson.articles;
      })
      .then( articles  => {
        props.navigation.navigate("Home", {articles: articles});
      })
      .catch( error => {
        console.error(error);
      });

    } , []);
    return (
        <View style={styles.container} >
            <ImageBackground style={styles.backgroundImage} source= style={styles.backgroundImage}>

                <View style={styles.logoContainer}>
                    <Text style={styles.logoText}>
                        Newzzz
          </Text>
                    <Text style={styles.logoDescription}>
                        Get your doze of daily news!
          </Text>

                </View>
            </ImageBackground>
        </View>
    );
}

When data is fetched, we use the navigate() method of the navigation object available from the props object to navigate to the Home route associated with HomeScreen and we pass in the articles data as a route parameter:

props.navigation.navigate("Home", {articles: articles});

For more information, see Passing parameters to routes.

Next, change HomeComponent as follows:

const HomeScreen = (props) => {
    return (
        <View>
            <FlatList
                data={ props.navigation.getParam("articles", []) }
                ListHeaderComponent={FlatListHeader}
                ItemSeparatorComponent={FlatListItemSeparator}
                keyExtractor={(item, index) => index.toString()}
                renderItem={({ item }) => <ArticleItem article={item} />}
            />
        </View>
    );
}

Instead of getting the articles data from the props object, we now need to retrieve it from the articles route parameter, passed from SplashScreen, using the getParam() method of the navigation object available from the props object.

That’s it. You should be able to have the same behavior as before using React Native navigation instead of conditional rendering.

Author: Ahmed Bouchefra Follow @ahmedbouchefra
Date: 11 Aug 2019

Adding Navigation using React Navigation & Switch Navigator

Restructuring our project code

React Navigation using createSwitchNavigator

React Navigation using `createSwitchNavigator`