Failed to post notification on channel “null” Target Api is 26

Question

Two log showing

1: Use of stream types is deprecated for operations other than volume control

2: See the documentation of setSound() for what to use instea

Answer 1

This issue is related to the old FCM version.

Update your dependency to com.google.firebase:firebase-messaging:15.0.2 or higher.

This will fix the error

failed to post notification on channel null

when your app receives notifications in the background because now Firebase provides a default notification channel with basic settings.

But you also can specify the default Notification Channel for FCM in the manifest.

To learn more here