Chat.js - User Listener Event - React Native Gifted Chat App

Chat.js

...
const Chat = (props) => {
  ...
  const userOnlineListenerId = useRef(uuidv4());
  ...
  useEffect(() => {
    if (selectedConversation) {
      ...
      // listen for online users.
      listenForOnlineUsers();
    }
    return () => {
      if (selectedConversation) {
        ...
        cometChat.removeUserListener(userOnlineListenerId);
      }
    }
  }, [selectedConversation]);
  ...
  const listenForOnlineUsers = () => {
    cometChat.addUserListener(
      userOnlineListenerId,
      new cometChat.UserListener({
        onUserOnline: onlineUser => {
          if (onlineUser && onlineUser.uid === selectedConversation.uid) {
            navigation.setOptions({
              headerTitle: () => renderChatHeaderTitle(onlineUser),
            })
          }
        },
        onUserOffline: offlineUser => {
          if (offlineUser && offlineUser.uid === selectedConversation.uid) {
            navigation.setOptions({
              headerTitle: () => renderChatHeaderTitle(offlineUser),
            })
          }
        }
      })
    );
  };
  ...
};
...