Before digging into the details of how to send Firebase push notification in Android using Firebase cloud messaging, it is useful to clarify what is push notification. For example, through push notification, our app can notify a user of new events. This happens even if the Android app is not working in the foreground. Using this service, we can send data from our server to our app whenever a new event occurs.
Setup
In top level gradle file
classpath 'com.google.gms:google-services:4.0.1'In module gradle file
//Add Firebase Core//
implementation 'com.google.firebase:firebase-core:16.0.1'
//Add FCM//
implementation 'com.google.firebase:firebase-messaging:17.3.4'
End of module gradle file
apply plugin: 'com.google.gms.google-services'