com.google.gwt.event.shared.HandlerManager.java Source code

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Here is the source code for com.google.gwt.event.shared.HandlerManager.java

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/*
 * 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;

/**
 * Manager responsible for adding handlers to event sources and firing those
 * handlers on passed in events. Primitive ancestor of {@link EventBus}, and
 * used at the core of {com.google.gwt.user.client.ui.Widget}.
 * <p>
 * While widget authors should continue to use
 * {@link com.google.gwt.user.client.ui.Widget#addDomHandler(EventHandler, com.google.gwt.event.dom.client.DomEvent.Type)}
 * and
 * {@link com.google.gwt.user.client.ui.Widget#addHandler(EventHandler, com.google.gwt.event.shared.GwtEvent.Type)}
 * , application developers are strongly discouraged from using a HandlerManager
 * instance as a global event dispatch mechanism.
 */
public class HandlerManager implements HasHandlers {

    @SuppressWarnings("deprecation")
    private static class Bus extends com.google.web.bindery.event.shared.SimpleEventBus {
        public Bus(boolean fireInReverseOrder) {
            super(fireInReverseOrder);
        }

        @Override
        protected <H> void doRemove(Event.Type<H> type, Object source, H handler) {
            super.doRemove(type, source, handler);
        }

        @Override
        protected <H> H getHandler(Event.Type<H> type, int index) {
            return super.getHandler(type, index);
        }

        @Override
        protected int getHandlerCount(Event.Type<?> eventKey) {
            return super.getHandlerCount(eventKey);
        }

        @Override
        protected boolean isEventHandled(Event.Type<?> eventKey) {
            return super.isEventHandled(eventKey);
        }
    }

    private final Bus eventBus;

    // source of the events
    private final Object source;

    /**
     * Creates a handler manager with a source to be set on all events fired via
     * {@link #fireEvent(GwtEvent)}. Handlers will be fired in the order that they
     * are added.
     * 
     * @param source the default event source
     */
    public HandlerManager(Object source) {
        this(source, false);
    }

    /**
     * Creates a handler manager with the given source, specifying the order in
     * which handlers are fired.
     * 
     * @param source the event source
     * @param fireInReverseOrder true to fire handlers in reverse order
     */
    public HandlerManager(Object source, boolean fireInReverseOrder) {
        eventBus = new Bus(fireInReverseOrder);
        this.source = source;
    }

    /**
     * Adds a handler.
     * 
     * @param <H> The type of handler
     * @param type the event type associated with this handler
     * @param handler the handler
     * @return the handler registration, can be stored in order to remove the
     *         handler later
     */
    public <H extends EventHandler> HandlerRegistration addHandler(GwtEvent.Type<H> type, final H handler) {
        return new LegacyHandlerWrapper(eventBus.addHandler(type, handler));
    }

    /**
     * Fires the given event to the handlers listening to the event's type.
     * <p>
     * Any exceptions thrown by handlers will be bundled into a
     * {@link UmbrellaException} and then re-thrown after all handlers have
     * completed. An exception thrown by a handler will not prevent other handlers
     * from executing.
     * <p>
     * Note, any subclass should be very careful about overriding this method, as
     * adds/removes of handlers will not be safe except within this
     * implementation.
     * 
     * @param event the event
     */
    public void fireEvent(GwtEvent<?> event) {
        // If it not live we should revive it.
        if (!event.isLive()) {
            event.revive();
        }
        Object oldSource = event.getSource();
        event.overrideSource(source);
        try {

            // May throw an UmbrellaException.
            eventBus.fireEvent(event);
        } catch (com.google.web.bindery.event.shared.UmbrellaException e) {
            throw new UmbrellaException(e.getCauses());
        } finally {
            if (oldSource == null) {
                // This was my event, so I should kill it now that I'm done.
                event.kill();
            } else {
                // Restoring the source for the next handler to use.
                event.overrideSource(oldSource);
            }
        }
    }

    /**
     * Gets the handler at the given index.
     * 
     * @param <H> the event handler type
     * @param index the index
     * @param type the handler's event type
     * @return the given handler
     */
    public <H extends EventHandler> H getHandler(GwtEvent.Type<H> type, int index) {
        return eventBus.getHandler(type, index);
    }

    /**
     * Gets the number of handlers listening to the event type.
     * 
     * @param type the event type
     * @return the number of registered handlers
     */
    public int getHandlerCount(GwtEvent.Type<?> type) {
        return eventBus.getHandlerCount(type);
    }

    /**
     * Does this handler manager handle the given event type?
     * 
     * @param e the event type
     * @return whether the given event type is handled
     */
    public boolean isEventHandled(GwtEvent.Type<?> e) {
        return eventBus.isEventHandled(e);
    }

    /**
     * Removes the given handler from the specified event type.
     * 
     * @param <H> handler type
     * 
     * @param type the event type
     * @param handler the handler
     */
    public <H extends EventHandler> void removeHandler(GwtEvent.Type<H> type, final H handler) {
        eventBus.doRemove(type, null, handler);
    }
}