Receive messages using Firebase Cloud Messaging

This guide describes how to set up Firebase Cloud Messaging in your mobile and web client apps so that you can reliably receive messages.

To receive messages, you can use a service that extends FirebaseMessagingService. Your service should override the onMessageReceived and onDeletedMessages callbacks. For a complete example, see the Firebase Cloud Messaging quickstart sample.

onMessageReceived is provided for most message types, with the following exceptions:

• Notification messages delivered when your app is in the background. In this case, the notification is delivered to the device's system tray. A user tap on a notification opens the app launcher by default.

• Messages with both notification and data payload, when received in the background. In this case, the notification is delivered to the device's system tray, and the data payload is delivered in the extras of the intent of your launcher Activity.

In summary:

For more information about message types, see Notifications and data messages.

The onMessageReceived callback has a short execution window. Many factors can affect how long this window is, including OS delays, app startup time, the main thread being blocked by other operations, or previous onMessageReceived calls taking too long.

For this reason, you should avoid long-running tasks (such as fetching images from a server to display in a notification) in onMessageReceived and instead schedule a task using WorkManager to handle any tasks that might take more than a couple of seconds to complete. For more information on message priority and how it impacts processing, see Message processing for high and normal priority messages.

Edit the app manifest

To use FirebaseMessagingService, you need to add the following in your app manifest:

<service
android:name=".java.MyFirebaseMessagingService"
android:exported="false">
<intent-filter>
<actionandroid:name="com.google.firebase.MESSAGING_EVENT"/>
</intent-filter>
</service>
AndroidManifest.xml 

It's recommended to set default values to customize the appearance of notifications. You can specify a custom default icon and a custom default color that are applied whenever equivalent values aren't set in the notification payload.

Add these lines inside the application tag to set the custom default icon and custom color:

<!--Setcustomdefaulticon.Thisisusedwhennoiconissetforincomingnotificationmessages.
SeeREADME(https://goo.gl/l4GJaQ)formore.-->
<meta-data
android:name="com.google.firebase.messaging.default_notification_icon"
android:resource="@drawable/ic_stat_ic_notification"/>
<!--Setcolorusedwithincomingnotificationmessages.Thisisusedwhennocolorissetfortheincoming
notificationmessage.SeeREADME(https://goo.gl/6BKBk7)formore.-->
<meta-data
android:name="com.google.firebase.messaging.default_notification_color"
android:resource="@color/colorAccent"/>
AndroidManifest.xml 

Android displays and uses the custom default icon for

• All notification messages sent from the Notifications composer.
• Any notification message that doesn't explicitly set the icon in the notification payload.

If a custom default icon isn't set and an icon isn't set in the notification payload, Android displays the application icon rendered in white.

Override onMessageReceived

By overriding the method FirebaseMessagingService.onMessageReceived, you can perform actions based on the received RemoteMessage object and get the message data:

overridefunonMessageReceived(remoteMessage:RemoteMessage){
// TODO(developer): Handle FCM messages here.
// Not getting messages here? See why this may be: https://goo.gl/39bRNJ
Log.d(TAG,"From: ${remoteMessage.from}")
// Check if message contains a data payload.
if(remoteMessage.data.isNotEmpty()){
Log.d(TAG,"Message data payload: ${remoteMessage.data}")
// Check if data needs to be processed by long running job
if(needsToBeScheduled()){
// For long-running tasks (10 seconds or more) use WorkManager.
scheduleJob()
}else{
// Handle message within 10 seconds
handleNow()
}
}
// Check if message contains a notification payload.
remoteMessage.notification?.let{
Log.d(TAG,"Message Notification Body: ${it.body}")
}
// Also if you intend on generating your own notifications as a result of a received FCM
// message, here is where that should be initiated. See sendNotification method below.
}
MyFirebaseMessagingService.kt 

@Override
publicvoidonMessageReceived(RemoteMessageremoteMessage){
// TODO(developer): Handle FCM messages here.
// Not getting messages here? See why this may be: https://goo.gl/39bRNJ
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());
if(/* Check if data needs to be processed by long running job */true){
// For long-running tasks (10 seconds or more) use WorkManager.
scheduleJob();
}else{
// Handle message within 10 seconds
handleNow();
}
}
// 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
// message, here is where that should be initiated. See sendNotification method below.
}
MyFirebaseMessagingService.java 

Override onDeletedMessages

In some situations, FCM may not deliver a message. This happens when there are too many messages (>100) pending for your app on a particular device at the time it connects or if the device hasn't connected to FCM in more than one month. In these cases, you may receive a callback to FirebaseMessagingService.onDeletedMessages(). When the app instance receives this callback, it should perform a full sync with your app server. If you haven't sent a message to the app on that device within the last 4 weeks, FCM won't call onDeletedMessages().

Handle notification messages in a backgrounded app

When your app is in the background, Android directs notification messages to the system tray. A user tap on the notification opens the app launcher by default.

This includes messages that contain both notification and data payload (and all messages sent from the Notifications console). In these cases, the notification is delivered to the device's system tray, and the data payload is delivered in the extras of the intent of your launcher Activity.

For more information into message delivery to your app, see the FCM reporting dashboard, which records the number of messages sent and opened on Apple and Android devices, along with data for "impressions" (notifications seen by users) for Android apps.