ListenerBloc<Event, State, Message> class abstract

Handles Listener's listen and close.

If your bloc needs to extend another class use Listener mixin.

Type argument Message marks what type of messages can be received.

See also:

  • ListenerCubit, a class extending Cubit which handles calling listen and cancel automatically.
  • useMessageListener, a hook that provides Listener's functionality which handles calling listen and cancel automatically.
Mixed in types


ListenerBloc(State initialState)


hashCode int
The hash code for this object.
no setterinherited
isClosed bool
Whether the bloc is closed.
no setterinherited
runtimeType Type
A representation of the runtime type of the object.
no setterinherited
state → State
The current state.
no setterinherited
stream Stream<State>
The current stream of states.
no setterinherited


add(Event event) → void
Notifies the Bloc of a new event which triggers all corresponding EventHandler instances.
addError(Object error, [StackTrace? stackTrace]) → void
Reports an error which triggers onError with an optional StackTrace.
cancel() → void
Stops receiving messages.
close() Future<void>
Closes the event and state Streams. This method should be called when a Bloc is no longer needed. Once close is called, events that are added will not be processed. In addition, if close is called while events are still being processed, the Bloc will finish processing the pending events.
emit(State state) → void
emit is only for internal use and should never be called directly outside of tests. The Emitter instance provided to each EventHandler should be used instead.
listen() → void
Starts message receiving.
noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent method or property is accessed.
on<E extends Event>(EventHandler<E, State> handler, {EventTransformer<E>? transformer}) → void
Register event handler for an event of type E. There should only ever be one event handler per event type E.
onChange(Change<State> change) → void
Called whenever a change occurs with the given change. A change occurs when a new state is emitted. onChange is called before the state of the cubit is updated. onChange is a great spot to add logging/analytics for a specific cubit.
onError(Object error, StackTrace stackTrace) → void
Called whenever an error occurs and notifies BlocObserver.onError.
onEvent(Event event) → void
Called whenever an event is added to the Bloc. A great spot to add logging/analytics at the individual Bloc level.
onInitialMessage(Message message) → void
Called when registering Listener if a message of type Message was sent earlier by Sender.
onMessage(Message message) → void
Called every time a new message is received.
onTransition(Transition<Event, State> transition) → void
Called whenever a transition occurs with the given transition. A transition occurs when a new event is added and a new state is emitted from a corresponding EventHandler.
toString() String
A string representation of this object.


operator ==(Object other) bool
The equality operator.