With React Native, you can build cross-platform mobile applications using JavaScript as the programming language. Each of your mobile apps may contain single or multiple user interfaces to serve a purpose.

Take, for example, Instagram. It consists of several different interfaces, such as a tool for sharing and displaying photos, a profile screen that contains details about the user, and an activity screen that contains a history of all likes and comments on each post.

What we’re building

In this tutorial, we are going to build one of the standard user interfaces from Instagram in React Native with a Firebase backend service. The Firebase will allow us to upload and query a real time server to fetch images and display them in the app.

The complete source code for the demo app is available at this Github repo.

Stack/Requirements

• Node.js >= 10.x.x version installed
• watchman
• react-native-cli
• react-navigation — an easy way to push screens to React Native apps
• react-native-ui-kitten – a great UI library based on Eva design system that contains UI components to speed up our development process and make our app look good
• Active Firebase project
• react-native-firebase
• react-native-image-picker

I will not be covering how to install modules such as react-native-firebase or react-native-image-picker and connect their native bindings. Please refer to their official documentation for that.

Setting up Navigation and UI Kitten

Before moving on to the rest of the tutorial, please make sure you have the following dependencies installed in your React Native project. Follow the commands in the sequence they are presented below.

react-native init instacloneApp

# after the project directory is created
cd instacloneApp

# install the following
yarn add react-navigation react-native-svg react-native-screens@1.0.0-alpha.23 react-native-gesture-handler react-native-reanimated react-navigation-tabs react-navigation-stack react-native-ui-kitten @eva-design/eva @ui-kitten/eva-icons uuid react-native-image-picker react-native-firebase

We are using the latest version of react-native-cli at the time of writing this post with react-native version 0.61.2.

To integrate react-navigation library, please follow the appropriate set of instructions depending on your react-native version here.

react-native-ui-kitten does provide interactive documentation. Make sure to configure the application root from the docs here just to verify that its related dependencies have been installed correctly.

import React from 'react'
import { mapping, light as lightTheme } from '@eva-design/eva'
import { ApplicationProvider, Layout, Text } from 'react-native-ui-kitten'

const ApplicationContent = () => (
  <Layout style={{ flex: 1, justifyContent: 'center', alignItems: 'center' }}>
    <Text>Welcome to UI Kitten</Text>
  </Layout>
)

const App = () => (
  <ApplicationProvider mapping={mapping} theme={lightTheme}>
    <ApplicationContent />
  </ApplicationProvider>
)

export default App

Note that UI kitten library comes with a default light and dark theme that your app can switch between. Once you modify the App.js file to the following above code snippet, you will get the following result. You will have to open two tabs in your terminal window.

# in the first window, run:
yarn start

# in the second window, depending on your development OS
react-native run-ios

# or

react-native run-android

Creating a Tab Navigator

The Instagram app contains five different screens that are accessible from tab navigation. Let us try to implement that interface in our React Native app with five different screens that contain some dummy presentation to display.

Create the src/ directory and inside it create a new folder called screens/. This folder will contain the following five screens.

• Feed.js
• Search.js
• AddPost.js
• Activity.js
• Profile.js

For now, you can add a dummy presentational component that just lists the screen name at the center when it is being currently viewed in the app. For example, the file Feed.js will look like below:

import React from 'react'
import { Text, Layout } from 'react-native-ui-kitten'

const Feed = () => (
  <Layout style={{ flex: 1, alignItems: 'center', justifyContent: 'center' }}>
    <Text>Feed Screen</Text>
  </Layout>
)

export default Feed

The screens/ directory will look like as below with five different files.

Next, create a new file TabNavigator.js inside the src/navigation directory. Import the required libraries and all the five screens.

import React from 'react'
import { createAppContainer } from 'react-navigation'
import { createBottomTabNavigator } from 'react-navigation-tabs'

import Feed from '../screens/Feed'
import Search from '../screens/Search'
import AddPost from '../screens/AddPost'
import Activity from '../screens/Activity'
import Profile from '../screens/Profile'

Eva design system comes with an open source icon library that we are going to use in this tutorial. You are free to use any other icon library as well.

Since the 4.x version of react-navigation library, all navigation patterns are separated in their npm packages.

Let us create a simple tab bar on the bottom of the screen with the following route configs.

const TabNavigator = createBottomTabNavigator({
  Feed: {
    screen: Feed
  },
  Search: {
    screen: Search
  },
  AddPost: {
    screen: AddPost
  },
  Activity: {
    screen: Activity
  },
  Profile: {
    screen: Profile
  }
})

export default createAppContainer(TabNavigator)

Using react-navigation, routes are lazily initialized by default. This means any screen component is not mounted until it becomes active first.

To integrate this tab navigator, open App.js and modify it:

import React from 'react'
import { mapping, light as lightTheme } from '@eva-design/eva'
import { ApplicationProvider } from 'react-native-ui-kitten'

import TabNavigator from './src/navigation/TabNavigator'

const App = () => (
  <ApplicationProvider mapping={mapping} theme={lightTheme}>
    <TabNavigator />
  </ApplicationProvider>
)

export default App

Here is the output:

The tab bar displays the name of the screen component.

Adding icons to the tab bar

Instead of displaying names for each screen, let us display the appropriate icons. We have already installed the icon library. Modify App.js to integrate icons from @ui-kitten/eva-icons which can be configured using IconRegistry.

import React, { Fragment } from 'react'
import { mapping, light as lightTheme } from '@eva-design/eva'
import { ApplicationProvider, IconRegistry } from 'react-native-ui-kitten'
import { EvaIconsPack } from '@ui-kitten/eva-icons'

import TabNavigator from './src/navigation/TabNavigator'

const App = () => (
  <Fragment>
    <IconRegistry icons={EvaIconsPack} />
    <ApplicationProvider mapping={mapping} theme={lightTheme}>
      <TabNavigator />
    </ApplicationProvider>
  </Fragment>
)

export default App

Note that if you are planning to use a third-party icon library such as react-native-vector-icons, you can learn more here on how to integrate that. Next, open the TabNavigator.js file. First, import the Icon component from react-native-ui-kitten.

import { Icon } from 'react-native-ui-kitten'

Each route in the BottomTabNavigator has access to different properties via navigationOptions object. You can hide the label or the name of each screen and display an icon in place of it by returning an Icon component on the tabBarIcon property inside navigationOptions.

Also, when a specific route on the screen is focused, its icon color should appear darker than the other icons in the tab bar to indicate that it is the active tab. This can be achieved using the prop focused on tabBarIcon.

Modify the tab navigator as follows:

const TabNavigator = createBottomTabNavigator(
  {
    Feed: {
      screen: Feed,
      navigationOptions: {
        tabBarIcon: ({ focused }) => (
          <Icon
            name='home-outline'
            width={32}
            height={32}
            fill={focused ? '#111' : '#939393'}
          />
        )
      }
    },
    Search: {
      screen: Search,
      navigationOptions: {
        tabBarIcon: ({ focused }) => (
          <Icon
            name='search-outline'
            width={32}
            height={32}
            fill={focused ? '#111' : '#939393'}
          />
        )
      }
    },
    AddPost: {
      screen: AddPost,
      navigationOptions: {
        tabBarIcon: ({ focused }) => (
          <Icon
            name='plus-square-outline'
            width={32}
            height={32}
            fill={focused ? '#111' : '#939393'}
          />
        )
      }
    },
    Activity: {
      screen: Activity,
      navigationOptions: {
        tabBarIcon: ({ focused }) => (
          <Icon
            name='heart-outline'
            width={32}
            height={32}
            fill={focused ? '#111' : '#939393'}
          />
        )
      }
    },
    Profile: {
      screen: Profile,
      navigationOptions: {
        tabBarIcon: ({ focused }) => (
          <Icon
            name='person-outline'
            width={32}
            height={32}
            fill={focused ? '#111' : '#939393'}
          />
        )
      }
    }
  },
  {
    tabBarOptions: {
      showLabel: false
    }
  }
)

To display an Icon from UI Kitten, you must provide attributes such as width and height.

The createBottomTabNavigator accepts the second parameter as a config object to modify the whole tab bar rather than each route. tabBarOptions is an object with different properties such hiding the label of each route by setting the boolean value of showLabel to false.

Adding a Header to the Feed screen

Since the Feed route is going to be the first screen that a user will see when they open the app, let’s display the name of the application in a header at the top. Also, this header can serve the purpose of navigating to a different route (such as Camera in the real app). To add a route that is accessible from the Feed screen and has nothing to do with the Tab bar, create a new stack navigator for the Feed screen separately and then add that in the TabNavigator.

Create a new file StackNavigator inside the navigation/ directory.

import React from 'react'
import { createAppContainer } from 'react-navigation'
import { createStackNavigator } from 'react-navigation-stack'
import Feed from '../screens/Feed'

export const FeedNavigator = createAppContainer(
  createStackNavigator({
    Feed: {
      screen: Feed,
      navigationOptions: {
        headerTitle: 'Social App'
      }
    }
  })
)

Modify TabNavigator.js and replace the Feed screen with FeedNavigator. Import it first.

// after other import statements
import { FeedNavigator } from './StackNavigator'

Then, replace the value of screen with FeedNavigator.

Feed: {
      screen: FeedNavigator,
      //... rest remains same
}

Create Feed UI

Let us begin by creating a simple UI for the Feed screen that will contain the image, title of the image, user avatar, and description of the image post. To begin, open Feed.js and import the following elements from react-native and react-native-ui-kitten.

import React, { Component } from 'react'
import { Image, View, TouchableOpacity } from 'react-native'
import { Text, Avatar, withStyles, List } from 'react-native-ui-kitten'

We are going to fetch some posts by mocking up a DATA array. Add this before the Feed component.

const DATA = [
  {
    id: 1,
    postTitle: 'Planet of Nature',
    avatarURI:
      'https://images.unsplash.com/photo-1559526323-cb2f2fe2591b?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=1050&q=80',
    imageURI:
      'https://images.unsplash.com/photo-1482822683622-00effad5052e?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=1050&q=80',
    randomText:
      'Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. '
  },
  {
    id: 2,
    postTitle: 'Lampost',
    avatarURI:
      'https://images.unsplash.com/photo-1559526323-cb2f2fe2591b?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=1050&q=80',
    imageURI:
      'https://images.unsplash.com/photo-1482822683622-00effad5052e?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=1050&q=80',
    randomText:
      'Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. '
  }
]

The List from React Native UI Kitten extends the basic FlatList from react-native to render a list of items. In a real application, having a Flat list is useful instead of ScrollView when there is a large number of data items in the list to render to the user.

It accepts the same amount of props as a normal flat list component. Return the following:

return (
  <List
    style={this.props.themedStyle.container}
    data={DATA}
    renderItem={renderItem}
    keyExtractor={DATA.id}
  />
)

We will come back to the style attribute in the next section. The data attribute accepts the value of a plain array, hence the mock DATA. Using keyExtractor forces the List to extract a unique key for each item in the list that is rendered. The renderItem attribute accepts what to display in the list, or how to render the data.

React Native UI kitten has a default ListItem component that you can use to display items, but since we need customization, let’s create our own. Add the following inside the render method of the component but before the return statement.

const renderItem = ({ item }) => (
  <View style={this.props.themedStyle.card}>
    <Image
      source={{ uri: item.imageURI }}
      style={this.props.themedStyle.cardImage}
    />
    <View style={this.props.themedStyle.cardHeader}>
      <Text category='s1' style={this.props.themedStyle.cardTitle}>
        {item.postTitle}
      </Text>
      <TouchableOpacity
        onPress={() => this.props.navigation.navigate('Profile')}>
        <Avatar
          source={{ uri: item.avatarURI }}
          size='small'
          style={this.props.themedStyle.cardAvatar}
        />
      </TouchableOpacity>
    </View>
    <View style={this.props.themedStyle.cardContent}>
      <Text category='p2'>{item.randomText}</Text>
    </View>
  </View>
)

The Avatar and Text are both UI components provided by the UI Kitten library. Avatar is a styled Image component, and so is Text. In the above snippet, notice how the category='p2' attribute is being used on the Text. UI Kitten provides these specific styles. You can explore more about it here.

Adding styles with High Order Function

The UI Kitten library provides a themed base design system that you can customize to your needs in form of a JSON object. It provides theme variables that can help you create custom themes based on some initial values and support React Native style properties at the same time.

This section will showcase how you can integrate its theme using a High Order Function (also known as a Higher Order Calculator, or HOC) in a React Native screen and without diving too much into customization. You can read more about it here.

We have already imported the withStyles HOC from UI Kitten. It accepts a component that can use the theme variables (in our case, the Feed component).

First, to identify the class component it accepts and the one it returns, edit the following line.

class _Feed extends Component {
  // ...
}

Add the following style while exporting the Feed component. These styles can be used in the style as props (which you have seen in the previous section).

export default Feed = withStyles(_Feed, theme => ({
  container: {
    flex: 1
  },
  card: {
    backgroundColor: theme['color-basic-100'],
    marginBottom: 25
  },
  cardImage: {
    width: '100%',
    height: 300
  },
  cardHeader: {
    padding: 10,
    flexDirection: 'row',
    alignItems: 'center',
    justifyContent: 'space-between'
  },
  cardTitle: {
    color: theme['color-basic-1000']
  },
  cardAvatar: {
    marginRight: 16
  },
  cardContent: {
    padding: 10,
    borderWidth: 0.25,
    borderColor: theme['color-basic-600']
  }
}))

Here is the output you get.

Create a Firebase Context

Before proceeding with this section, please make sure you have successfully followed instructions to install and integrate react-native-firebase library in your React Native app. Also, be sure that you have set up a Firebase app and have the right to access Firestore.

Using Context API, you can easily consume Firebase methods in the app without adding a state management library like Redux.

The common reason to use Context API in a React Native app is that you need to share some data in different places or components in the component tree. Manually passing props can be tedious as well as hard to keep track of.

The Context API consists of three building blocks:

• creating a context object
• declaring a provider that gives the value
• declaring a consumer that allows a value to be consumed (provided by the provider)

Create utils directory in src and add a new file Firebase.js. This file will contain two methods that will upload an image with relevant post data to the Firestore in a collection called post. The second method is used to fetch all the posts from the collection.

Using uuid package you can create a unique identifier for each post uploaded.

import firebase from 'react-native-firebase'
import uuid from 'uuid'

const Firebase = {
  uploadPost: post => {
    const id = uuid.v4()
    const uploadData = {
      id: id,
      postPhoto: post.photo,
      postTitle: post.title,
      postDescription: post.description,
      likes: []
    }
    return firebase
      .firestore()
      .collection('posts')
      .doc(id)
      .set(uploadData)
  },
  getPosts: () => {
    return firebase
      .firestore()
      .collection('posts')
      .get()
      .then(function(querySnapshot) {
        let posts = querySnapshot.docs.map(doc => doc.data())
        // console.log(posts)
        return posts
      })
      .catch(function(error) {
        console.log('Error getting documents: ', error)
      })
  }
}

export default Firebase

Next, create a new file called FirebaseContext.js. It will hold the snippet for creating the context and a High Order Function. The HOC will eliminate the need for importing and using Firebase. Wrapping each component as a parameter to the HOC will provide access to Firebase queries (or the custom methods created in Firebase.js) as props.

import React, { createContext } from 'react'

const FirebaseContext = createContext({})

export const FirebaseProvider = FirebaseContext.Provider

export const FirebaseConsumer = FirebaseContext.Consumer

export const withFirebaseHOC = Component => props => (
  <FirebaseConsumer>
    {state => <Component {...props} firebase={state} />}
  </FirebaseConsumer>
)

Create a new file index.js to export both the Firebase objects from the Firebase.js file, the provider and the HOC.

import Firebase from './Firebase'
import { FirebaseProvider, withFirebaseHOC } from './FirebaseContext'

export default Firebase

export { FirebaseProvider, withFirebaseHOC }

The provider has to grab the value from the context object for the consumer to use that value. This is going to be done in the App.js file. The value for the FirebaseProvider is going to be the Firebase object.

import React, { Fragment } from 'react'
import { mapping, light as lightTheme } from '@eva-design/eva'
import { ApplicationProvider, IconRegistry } from 'react-native-ui-kitten'
import { EvaIconsPack } from '@ui-kitten/eva-icons'

import Firebase, { FirebaseProvider } from './src/utils'
import TabNavigator from './src/navigation/TabNavigator'

const App = () => (
  <Fragment>
    <IconRegistry icons={EvaIconsPack} />
    <ApplicationProvider mapping={mapping} theme={lightTheme}>
      <FirebaseProvider value={Firebase}>
        <TabNavigator />
      </FirebaseProvider>
    </ApplicationProvider>
  </Fragment>
)

export default App

Uploading images to Firestore

Let us add modify the AddPost component to let the user choose an image from the phone’s gallery and store it on the Firestore database. Open the AddPost.js file and add the following import statements.

import React, { Component } from 'react'
import { Image, View } from 'react-native'
import { Text, Button, Input } from 'react-native-ui-kitten'
import ImagePicker from 'react-native-image-picker'
import { withFirebaseHOC } from '../utils'

Next, in the class component, add a state object that will track when the image file is picked from the gallery as well as when there are a title and a description provided for the image file. All of these three combined will create one post. You have seen the same the mock DATA array in Feed.js previously.

Use ImagePicker.launchImageLibrary() from react-native-image-picker to pick an image. Do note that this method expects an options object as the parameter. If an image is picked successfully, it will provide the URI of the image.

The onSubmit asynchronous method is responsible for uploading the post to the Firestore and clearing the state object when the post is successfully uploaded.

class AddPost extends Component {
  state = { image: null, title: '', description: '' }

  onChangeTitle = title => {
    this.setState({ title })
  }
  onChangeDescription = description => {
    this.setState({ description })
  }

  onSubmit = async () => {
    try {
      const post = {
        photo: this.state.image,
        title: this.state.title,
        description: this.state.description
      }
      this.props.firebase.uploadPost(post)

      this.setState({
        image: null,
        title: '',
        description: ''
      })
    } catch (e) {
      console.error(e)
    }
  }

  selectImage = () => {
    const options = {
      noData: true
    }
    ImagePicker.launchImageLibrary(options, response => {
      if (response.didCancel) {
        console.log('User cancelled image picker')
      } else if (response.error) {
        console.log('ImagePicker Error: ', response.error)
      } else if (response.customButton) {
        console.log('User tapped custom button: ', response.customButton)
      } else {
        const source = { uri: response.uri }
        console.log(source)
        this.setState({
          image: source
        })
      }
    })
  }

  render() {
    return (
      <View style={{ flex: 1, marginTop: 60 }}>
        <View>
          {this.state.image ? (
            <Image
              source={this.state.image}
              style={{ width: '100%', height: 300 }}
            />
          ) : (
            <Button
              onPress={this.selectImage}
              style={{
                alignItems: 'center',
                padding: 10,
                margin: 30
              }}>
              Add an image
            </Button>
          )}
        </View>
        <View style={{ marginTop: 80, alignItems: 'center' }}>
          <Text category='h4'>Post Details</Text>
          <Input
            placeholder='Enter title of the post'
            style={{ margin: 20 }}
            value={this.state.title}
            onChangeText={title => this.onChangeTitle(title)}
          />
          <Input
            placeholder='Enter description'
            style={{ margin: 20 }}
            value={this.state.description}
            onChangeText={description => this.onChangeDescription(description)}
          />
          <Button status='success' onPress={this.onSubmit}>
            Add post
          </Button>
        </View>
      </View>
    )
  }
}

export default withFirebaseHOC(AddPost)

Do not forget to wrap the component inside withFirebaseHOC. You will get the following screen.

Click on the button Add an image and choose the image from the device’s gallery or stored images.

Clicking the Add post button will submit the post to Firestore, which you can verify by opening the Firebase console. You will find a posts collection. An example is shown below:

Fetching posts from Firestore

In previous sections, you have observed that we are saving each post under a unique id as the name of the document under a collection called posts. To fetch all these documents, you will have to query the Firestore.

In the file utils/Firebase.js the function getPosts() does that for you. Using querySnapshot.docs.map you can fetch multiple documents at once from the Firestore database. All of these posts are going to be shown on the Feed screen, which is the entry point of the application. Right now, it only shows some mock data.

Open Feed.js and import the following statements.

import React, { Component } from 'react'
import { Image, View, TouchableOpacity, ActivityIndicator } from 'react-native'
import { Text, Avatar, withStyles, List } from 'react-native-ui-kitten'
import { withFirebaseHOC } from '../utils'

Next, in the class component, create a state object with two properties. The first property DATA is going to hold the array of all documents. The second property isRefreshing is going to be used in List to implement the functionality of fetching new results at pull to refresh.

class _Feed extends Component {
  state = { DATA: null, isRefreshing: false }
  // ...
}

Next, create a handler method called fetchPosts to fetch the data. Also, you have to explicitly call this method in the lifecycle method componentDidMount to load all posts available since Feed is the entry screen.

componentDidMount() {
    this.fetchPosts()
  }

  fetchPosts = async () => {
    try {
      const posts = await this.props.firebase.getPosts()
      console.log(posts)
      this.setState({ DATA: posts, isRefreshing: false })
    } catch (e) {
      console.error(e)
    }
  }

Next, add another method called onRefresh that is responsible for fetching posts when the screen is pulled downwards.

onRefresh = () => {
  this.setState({ isRefreshing: true })
  this.fetchPosts()
}

Here is how the rest of the component will look. While the data is being currently fetched, it will show a loading indicator on the screen.

render() {
    const renderItem = ({ item }) => (
      <View style={this.props.themedStyle.card}>
        <Image
          source={{ uri: item.postPhoto.uri }}
          style={this.props.themedStyle.cardImage}
        />
        <View style={this.props.themedStyle.cardHeader}>
          <Text category='s1' style={this.props.themedStyle.cardTitle}>
            {item.postTitle}
          </Text>
          <TouchableOpacity
            onPress={() => this.props.navigation.navigate('Profile')}>
            <Avatar
              source={{
                uri:
                  'https://images.unsplash.com/photo-1559526323-cb2f2fe2591b?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=1050&q=80'
              }}
              size='small'
              style={this.props.themedStyle.cardAvatar}
            />
          </TouchableOpacity>
        </View>
        <View style={this.props.themedStyle.cardContent}>
          <Text category='p2'>{item.postDescription}</Text>
        </View>
      </View>
    )

    if (this.state.DATA != null) {
      return (
        <List
          style={this.props.themedStyle.container}
          data={this.state.DATA}
          renderItem={renderItem}
          keyExtractor={this.state.DATA.id}
          refreshing={this.state.isRefreshing}
          onRefresh={() => this.onRefresh()}
        />
      )
    } else
      return (
        <View
          style={{ flex: 1, alignItems: 'center', justifyContent: 'center' }}>
          <ActivityIndicator size='large' />
        </View>
      )
  }

Lastly, wrap it up with the Firebase HOC.

export default Feed = withFirebaseHOC(
  withStyles(_Feed, theme => ({
    container: {
      flex: 1
    },
    card: {
      backgroundColor: theme['color-basic-100'],
      marginBottom: 25
    },
    cardImage: {
      width: '100%',
      height: 300
    },
    cardHeader: {
      padding: 10,
      flexDirection: 'row',
      alignItems: 'center',
      justifyContent: 'space-between'
    },
    cardTitle: {
      color: theme['color-basic-1000']
    },
    cardAvatar: {
      marginRight: 16
    },
    cardContent: {
      padding: 10,
      borderWidth: 0.25,
      borderColor: theme['color-basic-600']
    }
  }))
)

On the initial load, since there is only one post in the posts collection, the output will be the following:

Try adding one more post now and use pull to refresh to fetch the latest document from the posts collection.

Conclusion

There are many useful strategies for using Firebase and React Native together. Also, using a UI library like react-native-ui-kitten saves a lot of time over figuring out how to style each component.

The Feed screen we implemented is from one of the templates from Crowdbotics’ react-native collection. We use UI Kitten for our latest template libraries. You can modify the screen further by adding another component that takes care of counting likes or comments. Learn more about how to create custom screens like this from our open source project here.