Google suggests to use Firebase Cloud Messaging instead GCM. It's ok. Accepted.
In the foreground I can implement FirebaseMessagingService.onMessageReceived
and show 'custom' notification with localized message.
But how to implement localization of user notification messages, when application is in the background or wake-off?
This topic suggests:
Looks like you want to be handling the FCM messages yourself so you can customize the notification a bit more etc, so it would be better to not include the notification key in the POST payload, so all push messages are delivered to your onMessageReceived.
Yes, this resolved problem with background
state. But when android is in wake-off
state, no data-only notification received.