How Create Notification Topic For Firebase And Use This?

I can create notifications for single user and for all users in my app, but I can't understand and find information about notification with create topic. For this need create sepa

Solution 1:

There is no need to create a service when you want to subscribe to a topic. Just call anywhere in your app:

FirebaseMessaging.getInstance().subscribeToTopic("news");

Also see the section Subscribe the client app to a topic in the Firebase documentation.