onMessageReceived - это метод, который вызывается, когда клиент android получает сообщение от Firebase Cloud. Обычно мы создаем функцию для создания уведомления в этом методе.
И для чего, когда мы нажимаем уведомление, мы можем использовать pendingIntent.
Мы можем увидеть пример из Google в this github repo
public class MyFirebaseMessagingService extends FirebaseMessagingService {
private static final String TAG = "MyFirebaseMsgService";
// [START receive_message]
@Override
public void onMessageReceived(RemoteMessage remoteMessage) {
// TODO(developer): Handle FCM messages here.
Log.d(TAG, "From: " + remoteMessage.getFrom());
// Check if message contains a data payload.
if (remoteMessage.getData().size() > 0) {
Log.d(TAG, "Message data payload: " + remoteMessage.getData());
}
// Check if message contains a notification payload.
if (remoteMessage.getNotification() != null) {
Log.d(TAG, "Message Notification Body: " + remoteMessage.getNotification().getBody());
}
// Also if you intend on generating your own notifications as a result of a received FCM
sendNotification(remoteMessage.getNotification().getBody());
}
// [END receive_message]
/**
* Create and show a simple notification containing the received FCM message.
*
* @param messageBody FCM message body received.
*/
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 /* Request code */, intent,
PendingIntent.FLAG_ONE_SHOT);
Uri defaultSoundUri= RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this)
.setSmallIcon(R.drawable.ic_stat_ic_notification)
.setContentTitle("FCM Message")
.setContentText(messageBody)
.setAutoCancel(true)
.setSound(defaultSoundUri)
.setContentIntent(pendingIntent);
NotificationManager notificationManager =
(NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
notificationManager.notify(0 /* ID of notification */, notificationBuilder.build());
}
}