CometChat Flutter UIKit — Events & Listeners

Two event systems: SDK listeners (from CometChat server) and UI events (from UIKit components).

SDK Listeners (Server → App)

Register on CometChat SDK directly. These fire when the server pushes real-time data.

Available Listener Types

Listener Mixin	Register / Remove	Key Callbacks
MessageListener	CometChat.addMessageListener(id, this) / removeMessageListener(id)	onTextMessageReceived, onMediaMessageReceived, onCustomMessageReceived, onTypingStarted, onTypingEnded, onMessagesDelivered, onMessagesRead, onMessageEdited, onMessageDeleted
UserListener	CometChat.addUserListener(id, this) / removeUserListener(id)	onUserOnline, onUserOffline
GroupListener	CometChat.addGroupListener(id, this) / removeGroupListener(id)	onGroupMemberJoined, onGroupMemberLeft, onGroupMemberKicked, onGroupMemberBanned, onGroupMemberScopeChanged, onMemberAddedToGroup
CallListener	CometChat.addCallListener(id, this) / removeCallListener(id)	onIncomingCallReceived, onOutgoingCallAccepted, onOutgoingCallRejected, onIncomingCallCancelled
ConnectionListener	CometChat.addConnectionListener(id, this) / removeConnectionListener(id)	onConnected, onDisconnected, onConnecting, onFeatureThrottled

Registration Pattern

class _MyScreenState extends State<MyScreen>
    with MessageListener, UserListener {
  late final String _listenerId;

  @override
  void initState() {
    super.initState();
    _listenerId = 'my_screen_${DateTime.now().millisecondsSinceEpoch}';
    CometChat.addMessageListener(_listenerId, this);
    CometChat.addUserListener(_listenerId, this);
  }

  @override
  void dispose() {
    CometChat.removeMessageListener(_listenerId);
    CometChat.removeUserListener(_listenerId);
    super.dispose();
  }

  @override
  void onTextMessageReceived(TextMessage message) {
    // Handle incoming text message
  }

  @override
  void onUserOnline(User user) {
    // Handle user coming online
  }

  @override
  void onUserOffline(User user) {
    // Handle user going offline
  }
}

UI Events (UIKit Component → App)

These fire when UIKit components perform actions. Use these to react to user interactions across components.

CometChatMessageEvents

// Listen
CometChatMessageEvents.addMessagesListener('my_listener', MyMessageEventListener());

// Remove
CometChatMessageEvents.removeMessagesListener('my_listener');

// Key callbacks in CometChatMessageEventListener:
// ccMessageSent(BaseMessage message, MessageStatus status)  — inProgress/sent/error
// ccMessageEdited(BaseMessage message, MessageEditStatus status)
// ccMessageDeleted(BaseMessage message, EventStatus status)
// ccMessageRead(BaseMessage message)
// ccLiveReaction(String reaction)

CometChatUserEvents

CometChatUserEvents.addUsersListener('my_listener', MyUserEventListener());
CometChatUserEvents.removeUsersListener('my_listener');

// Key callbacks:
// ccUserBlocked(User user)
// ccUserUnblocked(User user)

CometChatGroupEvents

CometChatGroupEvents.addGroupsListener('my_listener', MyGroupEventListener());
CometChatGroupEvents.removeGroupsListener('my_listener');

// Key callbacks:
// ccGroupMemberKicked(Action, User kickedUser, User kickedBy, Group)
// ccGroupMemberBanned(Action, User bannedUser, User bannedBy, Group)
// ccGroupMemberScopeChanged(Action, User updatedUser, String newScope, String oldScope, Group)
// ccGroupCreated(Group)
// ccGroupDeleted(Group)
// ccGroupLeft(Action, User, Group)
// ccOwnershipChanged(Group, GroupMember)

CometChatConversationEvents

CometChatConversationEvents.addConversationListListener('my_listener', MyConvListener());
CometChatConversationEvents.removeConversationListListener('my_listener');

// Key callbacks:
// ccConversationDeleted(Conversation)

SDK vs UI Events — When to Use Which

Scenario	Use
Incoming message from another user	SDK MessageListener.onTextMessageReceived
Current user sent a message via composer	UI CometChatMessageEvents.ccMessageSent
Another user comes online	SDK UserListener.onUserOnline
Current user blocked someone via UIKit	UI CometChatUserEvents.ccUserBlocked
Group member kicked by another admin	SDK GroupListener.onGroupMemberKicked
Current user kicked someone via UIKit	UI CometChatGroupEvents.ccGroupMemberKicked

Key distinction: SDK listeners fire for remote events. UI events fire for local user actions performed through UIKit components.

BLoC Components Handle Listeners Automatically

The UIKit BLoCs (ConversationsBloc, MessageListBloc, etc.) register all necessary SDK listeners internally. You do NOT need to register listeners for components you're using — they handle their own real-time updates.

Register your own listeners only when you need to:

• Update custom UI outside UIKit components
• Track events for analytics
• Sync state between screens

ChatSDKEventInitializer

Called automatically by CometChatUIKit._initiateAfterLogin(). Bridges SDK events to UIKit's internal event bus. You never need to call this manually.

Gotchas

• Listener IDs MUST be unique per registration. Using the same ID overwrites the previous listener silently — no error thrown, old listener just stops receiving events.
• onTypingStarted/onTypingEnded only fire if subscriptionType was set in UIKitSettings. Omitting it silently disables all presence/typing events.
• SDK listeners fire on the main isolate. Heavy processing in callbacks blocks the UI thread. Offload to compute() if needed.
• ccMessageSent fires three times per message: once with MessageStatus.inProgress, once with MessageStatus.sent (success), or once with MessageStatus.error (failure). Filter by status.
• Connection listener's onConnected fires on reconnect — use it to trigger a silent refresh of your data.
• Group listener callbacks include an Action object (which is a BaseMessage subclass). Don't confuse it with the Action widget from Flutter.

Anti-Patterns

// ❌ WRONG — hardcoded listener ID causes silent overwrite
CometChat.addMessageListener('messages', this);
// Later, another screen does the same:
CometChat.addMessageListener('messages', this); // First listener silently lost!

// ✅ CORRECT — unique ID per instance
final id = 'screen_${DateTime.now().millisecondsSinceEpoch}';
CometChat.addMessageListener(id, this);

// ❌ WRONG — registering SDK listeners for a UIKit component you're already using
// ConversationsBloc already handles MessageListener, UserListener, GroupListener internally
CometChat.addMessageListener('redundant', this); // Duplicate handling

// ✅ CORRECT — only register for custom logic outside UIKit components
// Let ConversationsBloc handle its own listeners

// ❌ WRONG — not filtering ccMessageSent status
void onCcMessageSent(BaseMessage msg, MessageStatus status) {
  addToList(msg); // Adds 3 times! (inProgress + sent + error)
}

// ✅ CORRECT — filter by status
void onCcMessageSent(BaseMessage msg, MessageStatus status) {
  if (status == MessageStatus.sent) {
    addToList(msg);
  }
}

Checklist

• Listener IDs are unique (use timestamp or UUID suffix)
• All listeners registered in initState() are removed in dispose()
• subscriptionType set in UIKitSettings for presence/typing events
• ccMessageSent handlers filter by MessageStatus
• No redundant listeners for UIKit components that handle their own
• Action from CometChat SDK not confused with Flutter's Action widget (use import 'package:cometchat_chat_uikit/cometchat_chat_uikit.dart' as cc; and cc.Action)