org.obiba.opal.web.gwt.app.client.view.FadeAnimation.java Source code

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Here is the source code for org.obiba.opal.web.gwt.app.client.view.FadeAnimation.java

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/*******************************************************************************
 * Copyright 2008(c) The OBiBa Consortium. All rights reserved.
 *
 * This program and the accompanying materials
 * are made available under the terms of the GNU Public License v3.0.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ******************************************************************************/
package org.obiba.opal.web.gwt.app.client.view;

import com.google.gwt.user.client.DOM;
import com.google.gwt.user.client.Element;
import com.google.gwt.user.client.Timer;

/**
 * Fade an element, default is fade-in.
 */
public class FadeAnimation extends Timer {

    private double opacity;

    private double from = 0;

    private double to = 1;

    private int period = 1;

    private double step = 0.02;

    private final Element element;

    private FadedHandler handler;

    private FadeAnimation(Element element) {
        this.element = element;
    }

    @Override
    public void run() {
        if (from < to && opacity < to) {
            opacity += step;
            applyOpacity();
        } else if (from > to && opacity > to) {
            opacity -= step;
            applyOpacity();
        } else {
            if (handler != null) {
                handler.onFaded(element);
            }
            cancel();
        }
    }

    private void applyOpacity() {
        opacity = Math.max(opacity, 0);
        opacity = Math.min(opacity, 1);
        DOM.setStyleAttribute(element, "opacity", Double.toString(opacity));
    }

    private void start() {
        opacity = from;
        applyOpacity();
        scheduleRepeating(period);
    }

    /**
     * Callback when fading is over.
     */
    public interface FadedHandler {
        void onFaded(Element element);
    }

    public static class Builder {
        private final FadeAnimation fader;

        Builder(Element element) {
            fader = new FadeAnimation(element);
        }

        public Builder from(double from) {
            fader.from = Math.min(from, 1);
            return this;
        }

        public Builder to(double to) {
            fader.to = Math.max(to, 0);
            return this;
        }

        public Builder by(double step) {
            fader.step = step;
            return this;
        }

        public Builder every(int millis) {
            fader.period = millis;
            return this;
        }

        public Builder then(FadedHandler handler) {
            fader.handler = handler;
            return this;
        }

        public FadeAnimation start() {
            fader.start();
            return fader;
        }

    }

    public static Builder create(Element element) {
        return new Builder(element);
    }

    public static FadeAnimation start(Element element) {
        return create(element).start();
    }

}