Start Background service when app is in background

Question

How can I start an alarm using background services when we receive notification ? When my application is active then background service start easily, but when application is on background then background services can't run.

Answer 1

1. Why is this happening?

There are two types of messages in FCM (Firebase Cloud Messaging):

Display Messages: These messages trigger the onMessageReceived() callback only when your app is in foreground

Data Messages: Theses messages trigger the onMessageReceived() callback even if your app is in foreground/background/killed

override fun onMessageReceived(remoteMessage: RemoteMessage) {
    // ...

    // TODO(developer): Handle FCM messages here.
    // Not getting messages here? See why this may be:
    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}")

        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.
    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.
}