Firebase Cloud Messaging: Getting Started

Firebase Cloud Messaging (FCM) is a cross-platform messaging solution that lets you reliably deliver messages at no cost. Using FCM, you can notify a client app that a new email or some other data is available to you.

-Key capabilities:

-Send notification messages or data messages

Send notification messages that are displayed to your user or send data messages and determine completely what happens in your application code.

-Versatile message targeting

Distribute messages to your client app in any of three ways — to single devices, to groups of devices, or to devices subscribed to topics.

-Send messages from client apps

Send acknowledgments, chats, and other messages from devices back to your server over FCM’s reliable and battery-efficient connection channel.
(We will implement this third part in the next post)

-How does it work-

An FCM implementation includes an app server that interacts with FCM via HTTP or XMPP protocol, and a client app. You can compose and send messages using the app server or the Notifications console.

Firebase Notifications is built on Firebase Cloud Messaging and shares the same FCM SDK for client development. For testing or for sending marketing or engagement messages with powerful built-in targeting and analytics, you can use Notifications. For deployments with more complex messaging requirements, FCM is the right choice.

-Implementation:

Set up the FCM SDK

Set up Firebase and FCM on your app according the setup instructions for your platform.

Develop your client app

Add message handling, topic subscription logic, or other optional features to your client app. During the development, you can easily send test messages from the Notifications console.

Develop your app server

Decide which server protocol(s) you want to use to interact with FCM, and add logic to authenticate, build send requests, handle response, and so on. Note that if you want to use upstream messaging from your client applications, you must use XMPP.

1. Go to FireBase Console and create a new project by following the steps.
2. After syncing your project, create a class named MyFirebaseInstanceIDService.java and write the following code:

//Class extending FirebaseInstanceIdService
public class MyFirebaseInstanceIDService extends FirebaseInstanceIdService {

    private static final String TAG = "MyFirebaseIIDService";

    @Override
    public void onTokenRefresh() {
        
        //Getting registration token
        String refreshedToken = FirebaseInstanceId.getInstance().getToken();
        //Displaying token on logcat 
        Log.d(TAG, "Refreshed token: " + refreshedToken);
        
    }
}

3. Now create MyFirebaseMessagingService.java and write the following code:

public class MyFirebaseMessagingService extends FirebaseMessagingService {

    private static final String TAG = "MyFirebaseMsgService";

    @Override
    public void onMessageReceived(RemoteMessage remoteMessage) {
        //Displaying data in log
        //It is optional 
        Log.d(TAG, "From: " + remoteMessage.getFrom());
        Log.d(TAG, "Notification Message Body: " + remoteMessage.getNotification().getBody());
        
        //Calling method to generate notification
        sendNotification(remoteMessage.getNotification().getBody());
    }

    //This method is only generating push notification
    private void sendNotification(String messageBody) {
        Intent intent = new Intent(this, MainActivity.class);
        intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
        PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent,
                PendingIntent.FLAG_ONE_SHOT);

        Uri defaultSoundUri= RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
        NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this)
                .setSmallIcon(R.mipmap.ic_launcher)
                .setContentTitle("Firebase Notification")
                .setContentText(messageBody)
                .setAutoCancel(true)
                .setSound(defaultSoundUri)
                .setContentIntent(pendingIntent);

        NotificationManager notificationManager =
                (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);

        notificationManager.notify(0, notificationBuilder.build());
    }
}

4. Now define the above services in your AndroidManifest.xml file as follows:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="<your_package_name>">

    <!-- Adding Internet Permission -->
    <uses-permission android:name="android.permission.INTERNET"/>

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

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

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


5. Thats all. Now run your app (Make sure your device is having google play service or else it won’t work). After running the app you will be able to see a token in the logcat. Copy the token.

-Now steps for sending Push Notification using Firebase Console:
-Go to Firebase console and select the app you created.
-From the left menu select notification.
-Click on new message.
-Enter message, select single device and paste the token you copied and click on send.

That's all.. you can see a notification in the tray of your device.

Reference: https://firebase.google.com/docs/notifications/android/console-device