com.google.gwt.event.shared.GwtEvent Maven / Gradle / Ivy
/*
* Copyright 2009 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package com.google.gwt.event.shared;
import com.google.web.bindery.event.shared.Event;
/**
* Root of all GWT widget and dom events sourced by a {@link HandlerManager}.
* All GWT events are considered dead and should no longer be accessed once the
* {@link HandlerManager} which originally fired the event finishes with it.
* That is, don't hold on to event objects outside of your handler methods.
*
* There is no need for an application's custom event types to extend GwtEvent.
* Prefer {@link Event} instead.
*
* @param handler type
*/
public abstract class GwtEvent extends Event {
/**
* Type class used to register events with the {@link HandlerManager}.
*
* Type is parameterized by the handler type in order to make the addHandler
* method type safe.
*
*
* @param handler type
*/
public static class Type extends com.google.web.bindery.event.shared.Event.Type {
}
private boolean dead;
/**
* Constructor.
*/
protected GwtEvent() {
}
@Override
public abstract GwtEvent.Type getAssociatedType();
@Override
public Object getSource() {
assertLive();
return super.getSource();
}
/**
* Asserts that the event still should be accessed. All events are considered
* to be "dead" after their original handler manager finishes firing them. An
* event can be revived by calling {@link GwtEvent#revive()}.
*/
protected void assertLive() {
assert (!dead) : "This event has already finished being processed by its original handler manager, so you can no longer access it";
}
/**
* Should only be called by {@link HandlerManager}. In other words, do not use
* or call.
*
* @param handler handler
*/
protected abstract void dispatch(H handler);
/**
* Is the event current live?
*
* @return whether the event is live
*/
protected final boolean isLive() {
return !dead;
}
/**
* Kill the event. After the event has been killed, users cannot really on its
* values or functions being available.
*/
protected void kill() {
dead = true;
setSource(null);
}
/**
* Revives the event. Used when recycling event instances.
*/
protected void revive() {
dead = false;
setSource(null);
}
void overrideSource(Object source) {
super.setSource(source);
}
}