Build WordPress Client App with React Native #19 : Notify user when offline

This series intends to show how I build app to serve content from my WordPress blog by using react native. Since, my blog is talking about react-native, the series and the articles are interconnected. We will learn how to set-up many packages that make our lives comfortable and learn how to deal with WordPress APIs. Here, the most prominent features talked about in the book are the dark theme , offline mode, infinite scroll and many more. You can discover much more in this series.this inspiration to do this tutorial series came from the React Native App Templates from instamobile

In case of wanting to learn from the beginning, all the previous parts for this tutorial series are available below:

Here, we are going to integrate the offline mode to the app. This feature is very handy when we are out of connection and we can still access some of the features in the app. Here, we are just going to notify the network status and cache the data using react-native-NetInfo package. Caching will help to pull the data from the AsyncStorage during the offline mode.

Notify user when offline

Here, we are going to notify the user when we are offline. For that, we are going to display network status. Hence, we need to create a new file called NetworkStatus.js in component folder.

Then, we need to install the netinfo package into our project. For that, we need to run the following command in our project directory:

yarn add @react-native-community/netinfo

Then, we need to link the package to native files as we did in previous installation.

In Android, we need to add a configuration to ‘./android/build.gradle file:

buildscript {
  ext {
    buildToolsVersion = "28.0.3"
    minSdkVersion = 16
    compileSdkVersion = 28
    targetSdkVersion = 28
    androidXCore = "1.0.2"
    // Put here other AndroidX dependencies
  }

Now, we need to make the following imports to the NetworkStatus.js file:

import React from 'react';
import {List} from 'react-native-paper'
import NetInfo from '@react-native-community/netinfo';
import {Text, StyleSheet} from 'react-native';

Then, we need to define a new function called handleConnectivityChange function as shown in the code snippet below

export default class NetworkProvider extends React.Component {
  state = {
    isConnected: true,
  };

  componentDidMount() {
    NetInfo.isConnected.addEventListener(
      'connectionChange',
      this.handleConnectivityChange,
    );
  }

  componentWillUnmount() {
    NetInfo.isConnected.removeEventListener(
      'connectionChange',
      this.handleConnectivityChange,
    );
  }

  handleConnectivityChange = isConnected => {
    this.setState({isConnected});
    console.log(this.state.isConnected);
  };

Here, we have defined a state variable called isConnected which handles the connection info. Then, we have defined a function called handleConnectivityChange which takes the isConnected parameter. Then, we have called the function in the addEventListener function provided by the NetInfo module in the componentDidMount hook to subscribe to network change. And, we have also called the function in the removeEventListener function of NetInfo module in the componentWillUnmount hook to unsubscribe from network change.

Now, we need to the template to display the offline mode. For that, we need to use the code from the following code snippet:

render() {
    const iconPrefix = Platform.OS === 'ios' ? 'ios' : 'md';
    return this.state.isConnected ? (
      <Text></Text>
    ) : (
      <List.Item
      title="Offline mode"
      left={() => <List.Icon icon="airplane-off" />}
      
    />
    );
  }
}

const styles = StyleSheet.create({

  offLine: {
    marginRight: 15,
    flexDirection: 'row',
  },
});

Here, we have returned the template based in isConnected state. If true, it returns null else it returns Item component with airplane mode icon.

Now, we need to show the icon in every screen header if we are offline. For that, we need to import the NetworkStatus.js file in the Navigator file as shown in the code snippet below:

import NetworkStatus from './NetworkStatus';

Then, we need to include it to the headerRight option of the navigationOptions config as shown in the code snippet below:

{
    navigationOptions: ({navigation}) => {
      const {routeName} = navigation.state.routes[navigation.state.index];

      return {
        headerTitle: routeName,
        headerRight: <NetworkStatus />,
      };
    },
  },

Hence, we will get following result in the emulator screens if we disconnect:

Summary

In this chapter, we learned how to implement the offline mode in the react native app. We used the netinfo package to display the offline icon in the header by checking the network status of the device.

Also published on Medium.