ch.sebastienzurfluh.swissmuseum.core.client.view.animations.ScrollToTheTop.java Source code

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Here is the source code for ch.sebastienzurfluh.swissmuseum.core.client.view.animations.ScrollToTheTop.java

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/*
 * Copyright 2012-2013 Sebastien Zurfluh
 * 
 * This file is part of "Parcours".
 * 
 * "Parcours" is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * "Parcours" is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 *  You should have received a copy of the GNU General Public License
 *  along with "Parcours".  If not, see <http://www.gnu.org/licenses/>.
 */

package ch.sebastienzurfluh.swissmuseum.core.client.view.animations;

import com.google.gwt.animation.client.Animation;
import com.google.gwt.user.client.Window;

/**
 * This singleton scrolls the page to the top when ordered to.
 *
 *
 * @author Sebastien Zurfluh
 *
 */
public class ScrollToTheTop extends Animation {
    private int destination = 0;
    private int origin = 0;

    private static ScrollToTheTop instance;

    private ScrollToTheTop() {
        origin = Window.getScrollTop();
    }

    /**
     * @return the unique instance of this animation
     */
    public static ScrollToTheTop getInstance() {
        if (instance == null) {
            instance = new ScrollToTheTop();
        }
        return instance;
    }

    /**
     * Starts the animation.
     */
    public void start() {
        run(400);
    }

    @Override
    protected void onUpdate(double progress) {
        Window.scrollTo(0, (int) (origin + (destination - origin) * progress));
    }

}