How to make a GCM / FCM notification-type message non-collapsible

Question

Google Cloud Messaging (GCM) support two types of push messages: "notification" messages and "data" messages. According to the documentation, notification messages are collapsible by default, while data messages are non-collapsible by default.

In order to make a data message collapsible, you need to specifiy a collapseKey. My question is: How can you make a notification message non-collapsible?

Note: The question applies to Firebase Cloud Messaging (FCM) as well.

Answer 1

The message concepts and options documentation states:

messages are non-collapsible by default except for notification messages, which are always collapsible

But then later on the same page, it goes on to say:

except for notification messages, all messages are non-collapsible by default

Which is somewhat ambiguous. However, in the payload section, it states:

[notification messages] may have optional data payload. Always collapsible

Therefore, it doesn't seem possible to make notification messages non-collapsible.

I'd suggest that this is by design, because when creating notifications in Android, they are automatically replaced when another notification with the same ID is posted (similarly to how collapsing messages works). If I remember correctly, FCM/GCM uses the same ID for all notification messages.

Possible solution

If you do want a non-collapsible notification message, I'd suggest sending a data-only payload (with no notification or collapseKey), and then overriding the onMessageReceived() from the FirebaseMessagingService to create your own notification.

There is an example of this available on the Android quickstart sample:

@Override
public void onMessageReceived(RemoteMessage remoteMessage) {
    // ...

    // Check if message contains a data payload.
    if (remoteMessage.getData().size() > 0) {
        Log.d(TAG, "Message data payload: " + remoteMessage.getData());

        // ...
    }

    // ...

    // 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.
}

The last comment there points you to the example sendNotification() method.

For your scenario, you'll need to pass a unique ID to the notificationManager.notify() call so that Android creates a new notification and does not replace any existing notifications - therefore, making the message non-collapsible.