asquare.gwt.debug.client.EventPreviewDispatcher.java Source code

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Here is the source code for asquare.gwt.debug.client.EventPreviewDispatcher.java

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/*
 * Copyright 2006 Mat Gessel <mat.gessel@gmail.com>
 * 
 * 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 asquare.gwt.debug.client;

import java.util.ArrayList;

import com.google.gwt.user.client.DOM;
import com.google.gwt.user.client.Event;
import com.google.gwt.user.client.EventPreview;

/**
 * The {@link EventPreview} facility adds listeners to a stack, and only the
 * listener on top of the stack previews events. This class distributes events
 * to 1 or more listeners if it is on top of the stack. It will be pushed down
 * the stack if a {@link com.google.gwt.user.client.ui.PopupPanel PopupPanel} or
 * {@link com.google.gwt.user.client.ui.DialogBox DialogBox} is shown.
 */
public final class EventPreviewDispatcher implements EventPreview {
    private static EventPreviewDispatcher s_instance = new EventPreviewDispatcher();

    private final ArrayList m_listeners = new ArrayList();

    private boolean m_installed = false;

    private EventPreviewDispatcher() {
    }

    /**
     * Adds the specified listener. If <code>listener</code> is the first
     * listener added, the dispatcher will be added to the top of the
     * {@link DOM#addEventPreview(com.google.gwt.user.client.EventPreview) EventPreview}
     * stack.
     * 
     * @param listener
     */
    public static void addListener(DebugEventListener listener) {
        s_instance.m_listeners.add(listener);
        if (!s_instance.m_installed) {
            DOM.addEventPreview(s_instance);
            s_instance.m_installed = true;
        }
    }

    /**
     * Removes the specified listener. If <code>listener</code> is only
     * remaining listener, the dispatcher will be removed from the
     * {@link DOM#addEventPreview(com.google.gwt.user.client.EventPreview) EventPreview}
     * stack.
     * 
     * @param listener
     */
    public static void removeListener(DebugEventListener listener) {
        s_instance.m_listeners.remove(listener);
        if (s_instance.m_listeners.size() == 0) {
            DOM.removeEventPreview(s_instance);
            s_instance.m_installed = false;
        }
    }

    // EventPreview listener method
    public boolean onEventPreview(Event event) {
        if (m_listeners.size() > 0) {
            Object[] listeners = m_listeners.toArray();
            for (int i = 0; i < listeners.length; i++) {
                DebugEventListener listener = (DebugEventListener) listeners[i];
                listener.eventDispatched(event);
            }
        }
        return true;
    }
}