Handle User Presence with Your Own Logic

Collaboration Kit includes a manager to set the user presence in a topic, keep track of the users who are currently present, and react to changes in the presence. It provides a simple and flexible way to manage topic data related to user presence and makes it easy to create custom components with collaborative features.

The following example has a custom component that shows the list of active users in a topic using the presence manager:

VerticalLayout users = new VerticalLayout();

UserInfo localUser = new UserInfo("john");

PresenceManager manager = new PresenceManager(users, localUser,
        "my-topic"); // (1)

manager.markAsPresent(true); // (2)

manager.setPresenceHandler(context -> { // (3)
    Component card = createUserCard(context.getUser());
    users.add(card);
    return () -> users.remove(card); // (4)
});

Creating a PresenceManager takes:
- a component to bind the manager connection context to the UI,
- an instance of UserInfo that represents the current local user, and
- the ID of the topic to connect to.
The markAsPresent() method is used to configure the manager to mark the local user as present in the topic as soon as a connection is established.
The setPresenceHandler method sets a callback to handle a new user joining the topic. The UserInfo for the new user is provided by the context passed as the argument to the callback.
The callback returns another callback, a registration, that’s called to remove the same user when the user leaves the topic.

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Documentation

Documentation

Handle User Presence with Your Own Logic