I think you want to implement firebase to your app to show notifications.
use push-notifications.
steps:
-
add firebase to your android project . you can see the step by step here.
https://firebase.google.com/docs/android/setup -
the next step is to read and write data to firebase.
https://firebase.google.com/docs/database/android/read-and-write
here when you read the data you can push notification.
if you want any further help ping me