User Presence
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The SDK also offers functionality to query and synchronize the presence of other users, enabling the creation of a UI that displays their online status. For example, you might use a green dot to indicate whether a particular user is online or offline.
Within the SDK, a user's presence is represented by the AmityUserPresence object, which contains three properties.
userId
Id of the user
lastHeartbeat
Timestamp when that user last synced its heartbeat with the server.
isOnline
Convenient property to determine online status. User is considered online if its lastHeartbeat has been within last 60 seconds.
The SDK enables users to query the presence state for a list of users, with a maximum limit of 220. The getUserPresence method from the AmityUserPresenceRepository class can be used to fetch a list of AmityUserPresence objects.
In addition to querying user presence, the SDK also offers a method to periodically sync the presence of other users. This functionality keeps users informed about the online status of others. One application of this feature would be to display a list of users and provide an online indicator for those who are currently online.
The SDK includes the syncUserPresence(id, viewId) method in the AmityUserPresenceRepository class to synchronize the presence of another user. This method adds the specified ID to the list of user IDs for presence synchronization, occurring periodically at set intervals. To observe the results of this process, use the getSyncingUserPresence() method. When presence information is obtained for the currently syncing user IDs, notifications are sent through the observer returned from the getSyncingUserPresence() method. For further details on observing presence, refer to the Observe User Presence section.
For optimal use, particularly when displaying a list of users, call this method as a list item appears to synchronize the user's presence state. Conversely, utilize the unsyncUserPresence(id, viewId) method to stop synchronization when a list item is no longer visible, ensuring that the maximum sync limit is never reached.
This syncUserPresence(id, viewId) method also provides an optional viewId parameter. viewId is the unique id of the view that this user id is tied to. In most cases, you do not need to specify any value to this parameter. viewId is useful if you want to bind the same user id to multiple views on the same screen. In that case, if you want to unsync presence for one view, it won't affect presence syncing for the same user id in another view.
The SDK includes the unsyncUserPresence(id, viewId) method to cease syncing the presence of a specific user ID. When a user ID is unsynced, the SDK removes it from the current list of synced IDs, and the observer returned from the getSyncingUserPresence() method will no longer provide presence information for that user. The method also features an optional viewId parameter, functioning similarly to the syncUserPresence(id, viewId) method.
The SDK also provides a convenient method to unsync all user ids that are currently being synced. This is particularly useful when you don’t care about the user ids being synced. One use case for this is when the user navigates to another screen that does not care about syncing previously synced users at all. So you can call unsyncAllUserPresence() method when the previous screen disappears.
After adding users for synchronization, the next step involves observing their presence. The SDK offers an observer via the getSyncingUserPresence() method. Whenever presence information is retrieved for users synced through syncUserPresence(id, viewId), this information is published through the observer.
Accessing User Presence:
You can access the presence information for synced users in two ways:
Through the Observer Returned from getSyncingUserPresence(): When the presence information is updated, the observer provides an array of [AmityUserPresence] the user IDs being synced. Users need to map AmityUserPresence from this array to the view where the information is to be displayed.
Through the AmityUser Object: When presence information is fetched from the server, the lastHeartbeat timestamp is mapped to the lastHeartbeat property of the AmityUser object, if available. Users can directly access the lastHeartbeat property from the AmityUser object to determine whether a user is online or offline.
The SDK provides the getOnlineUsersCount method in the AmityUserPresenceRepository class to query the count of online users. Please note that this count does not update automatically.
The SDK provides a method getOnlineUsersSnapshot in AmityUserPresenceRepository to query a list of online users in a network. The list of users can be accessed through user property which returns an array of AmityUser.
When this snapshot object is initialized, it fetches the snapshot of user presences of all online users in current network. Then it maps that information to AmityUser per page and provides a list of AmityUser with pagination. Each page can contain a maximum of 20 users. When the snapshot is returned, it will contain users for the first page. You can still fetch more users if available through the loadMore() method. Once more users are fetched, the user can access those users through the user's property. You can also use the canLoadMore property to determine if more online users can be fetched.