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copied! <p>Since this question and the answer from Piotr GWT has added support for a slightly different way to create custom events. This event implementation is specific build to be used with the GWT's EventBus in the package <code>com.google.web.bindery.event.shared</code>. An example on how to build a custom event for GWT 2.4:</p> <pre class="lang-java prettyprint-override"><code>import com.google.web.bindery.event.shared.Event; import com.google.web.bindery.event.shared.EventBus; import com.google.web.bindery.event.shared.HandlerRegistration; /** * Here is a custom event. For comparison this is also a MessageReceivedEvent. * This event extends the Event from the web.bindery package. */ public class MessageReceivedEvent extends Event<MessageReceivedEvent.Handler> { /** * Implemented by methods that handle MessageReceivedEvent events. */ public interface Handler { /** * Called when an {@link MessageReceivedEvent} event is fired. * The name of this method is whatever you want it. * * @param event an {@link MessageReceivedEvent} instance */ void onMessageReceived(MessageReceivedEvent event); } private static final Type<MessageReceivedEvent.Handler> TYPE = new Type<MessageReceivedEvent.Handler>(); /** * Register a handler for MessageReceivedEvent events on the eventbus. * * @param eventBus the {@link EventBus} * @param handler an {@link MessageReceivedEvent.Handler} instance * @return an {@link HandlerRegistration} instance */ public static HandlerRegistration register(EventBus eventBus, MessageReceivedEvent.Handler handler) { return eventBus.addHandler(TYPE, handler); } private final String message; public MessageReceivedEvent(String message) { this.message = message; } @Override public Type<MessageReceivedEvent.Handler> getAssociatedType() { return TYPE; } public String getMessage() { return message; } @Override protected void dispatch(Handler handler) { handler.onMessageReceived(this); } } </code></pre> <p>The event is used as follows:</p> <p>To register your handler for this event with the eventbus call the static register method on the MessageReceivedEvent class:</p> <pre class="lang-java prettyprint-override"><code>MessageReceivedEvent.register(eventbus, new MessageReceivedEvent.Handler() { public void onMessageReceived(MessageReceivedEvent event) { //...do something usefull with the message: event.getMessage(); } }); </code></pre> <p>Now to fire the event on the eventbus call <code>fireEvent</code> with a newly constructed event:</p> <pre class="lang-java prettyprint-override"><code>eventBus.fireEvent(new MessageReceivedEvent("my message")); </code></pre> <p>Another implementation can be found in GWT's own <code>EntityProxyChange</code> event class. That implementation uses a alternative option of the EventBus. It uses the ability to add handlers that are bound to a specific source, via <code>addHandlerToSource</code> and can be triggered via <code>eventBus.fireEventFromSource</code>.</p> <p>The event implementation given here is also more suitable when working with GWT's <a href="http://code.google.com/webtoolkit/doc/latest/DevGuideMvpActivitiesAndPlaces.html" rel="noreferrer">Activities</a>.</p>

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