Sending Push Notifications to Android with Firebase

The 2016 Google I/O announced major improvements to their amazing product – Firebase – a cloud platform with a lot of amazing features for mobile app developers. One of them is Firebase Cloud Messaging (FCM) — a cross-platform messaging solution that lets users reliably deliver messages at no cost. Yes, FCM is a free service from Google. Comparing to the earlier Google Cloud Messaging (GCM), FCM is much more developer-friendly because you don't even need to see any of the server code involved.

This is a tutorial about sending push notifications to Android through Firebase, based on the new release of Firebase this year (2016). This tutorial shows how to setup the skeleton for sending and receiving push notifications via FCM with instructions on server code.

After reading this tutorial, I hope that you will be able to use it in your new Android app or add it to your existing app for sending out push notifications. Let's start!

Who Should Read This Tutorial

• You are going to have push notifications function in your new Android app
• You are going to replace your current push notification provider (such as Parse) to a new one
• You have an app which uses GCM. FCM is the new version of GCM with new features.

Before We Start

You'll need the following:

• The latest stable Android Studio
• A Firebase account

1. Get started

Add a new project or import an existing project to Firebase console.

If you choose to create a new project, you need to set the project name and country. For example, I will call my project FirebaseDemo.

Then select "Add Firebase to your Android app".

Set a package name for your app. I only set my package name and omit the SHA-1 because I don't use Firebase for my app's authentication.

Click the ADD APP button here to download google-services.json. This is an important file and you will need to put it into your app.

2. Add google-services.json to your app folder

Replace the google-services.json in your app folder. The Google services plugin for Gradle will load the google-services.json file you just downloaded.

3. Configure gradle files

Open Android Studio and modify your build.gradle files to use the Google services plugin.

(3.1) Update the project-level build.gradle (the one in your project folder)

Add the following line to the build.gradle file:

buildscript {
  dependencies {
    classpath 'com.google.gms:google-services:3.0.0' // Add this line
  }
}

(3.2) Update the app-level build.gradle (the one in your project/your app-module)

(a) Add this line to the bottom of the build.gradle file

apply plugin: 'com.google.gms.google-services'

(b) Add Firebase related dependencies

And Firebase related dependencies under dependencies in the same build.gradle file.

dependencies {
    compile 'com.google.firebase:firebase-core:9.2.0'                        // this line must be included to integrate with Firebase
    compile 'com.google.firebase:firebase-messaging:9.2.0'                   // this line must be included to use FCM
}

(c) Update services using com.google.android.gms:play-services

If you add Firebase into an existing project which uses any function of gms:play-services, such as gps location,
you have to update their versions, too. Upon writing this tutorial, 9.2.0 works well. If you get compilation problems, you need to check find out the correct version number.

   compile 'com.google.android.gms:play-services-location:9.2.0'  
   compile 'com.google.android.gms:play-services-places:9.2.0'  

(d) Add the applicationId to the defaultConfig section

android {

    defaultConfig {
        applicationId "com.example.my.app"  // this is the id that your app has
    }
}

4. Add services to your app

Two services should be added to use Firebase Cloud Messaging service: a basic code for testing if push notification works, and other codes to handle receiving message or sending message in your app according to your design.

(1) Add a service that extends FirebaseMessagingService

To be able to receive any notification in your app, you should add a service which extends FirebaseMessagingService like this:

public class MyFirebaseMessagingService extends FirebaseMessagingService {
 private static final String TAG = "FCM Service";
 @Override
    public void onMessageReceived(RemoteMessage remoteMessage) {
        // TODO: Handle FCM messages here.
        // If the application is in the foreground handle both data and notification messages here.
        // Also if you intend on generating your own notifications as a result of a received FCM
        // message, here is where that should be initiated.
        Log.d(TAG, "From: " + remoteMessage.getFrom());
        Log.d(TAG, "Notification Message Body: " + remoteMessage.getNotification().getBody());
    }
}

Then add it into the AndroidManifest.xml file.

        <service android:name=".MyFirebaseMessagingService">
            <intent-filter>
                <action android:name="com.google.firebase.MESSAGING_EVENT"/>
            </intent-filter>
        </service>

(2) Add a service that extends FirebaseInstanceIdService

public class FirebaseIDService extends FirebaseInstanceIdService {
    private static final String TAG = "FirebaseIDService";

    @Override
    public void onTokenRefresh() {
        // Get updated InstanceID token.
        String refreshedToken = FirebaseInstanceId.getInstance().getToken();
        Log.d(TAG, "Refreshed token: " + refreshedToken);

        // TODO: Implement this method to send any registration to your app's servers.
        sendRegistrationToServer(refreshedToken);
    }

    /**
     * Persist token to third-party servers.
     *
     * Modify this method to associate the user's FCM InstanceID token with any server-side account
     * maintained by your application.
     *
     * @param token The new token.
     */
    private void sendRegistrationToServer(String token) {
        // Add custom implementation, as needed.
    }
}

Add it into the AndroidManifest.xml file, this makes sure that the service is loaded

        <service android:name=".FirebaseIDService">
            <intent-filter>
                <action android:name="com.google.firebase.INSTANCE_ID_EVENT"/>
            </intent-filter>
        </service>

5. Test and send your first push notification!

To see if the setup works, run a test by sending a test message to your own mobile.

Write down your message and choose an app. Click "SEND MESSAGE".

Now you should get a push notification on your Android mobile. If your app is running on the background, you will get it on the mobile's notification center; otherwise you can see it in your Android Monitor log (we have to put a code to log incoming messages) like this.

If the setup is successful, you should get a notification on your mobile. Sometimes, it can take a couple of minutes for the message to send and arrive, so just be patient for a little while.

6. Possible problems

• Compilation problems can be related to wrong version numbers in your build.gradle files.
• If you see a message like "com.google.firebase.crash.FirebaseCrash is not linked. Skipping initialization." in your
  Android Monitor log, it is ok because we don't use this Firebase Crash Analytics service.
• Firebase initialization is not starting

We are done!

Now you have the basic idea on how to send push notifications on Android with Firebase. Good luck with your project!

The second part to this series will discuss how you can customize the push notifications you want to send out! Read it here!

Reference

https://firebase.google.com/docs/notifications/