What is the best way to generate Push notification using Firebase?

Question

I have the following problem:

I have a system where it is possible to register a series of tasks to be accomplished by a team or person. What I need is that whenever an order is finalized by a user, all others receive a notification (Push) saying it has been completed.

My doubts are:

a) Assuming that users can enter or leave the solver groups, this would be more recommended. Push to: Topics, Groups or single?

b) How to prevent Push from being generated after the user logs off into the app?

The solver groups would have a model similar to What’s app groups. If the user leaves the group, he is no longer notified.

Answer 1

a) Short answer: Topics.

Long answer:

Single Devices would require you to create your own logic for the user to log in and out of groups. You would have to store each user’s token in a database (which can be more expensive depending on the limits of your database).

Groups - although the name is suggestive, the documentation indicates that groups are for you to push to all devices that belong to a user. For example, if one of your users uses the app on iPhone, an Android tablet, and a computer (via the Web), you would put those 3 devices in a group to receive the same notifications at all times.

Topics - Just like in groups, you don’t need to manage the tokens of each device that is part of a "group" (other than the single Devices) because Firebase does it for you. And the SDK is very easy to use. For a user to join a group, you would:

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

And for him to leave the group:

FirebaseMessaging.getInstance().unsubscribeFromTopic("idGroup");

b) If you are using Firebase Auth, when logging off it will no longer have access to push Notifications. If you’re not using Auth, try calling deleteInstanceId() during the log off.