com.google.gwt.demos.gwtcanvas.client.LogoDemo.java Source code

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Here is the source code for com.google.gwt.demos.gwtcanvas.client.LogoDemo.java

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/*
 * Copyright 2008 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.demos.gwtcanvas.client;

import com.google.gwt.dom.client.ImageElement;
import com.google.gwt.user.client.Timer;
import com.google.gwt.user.client.Window;
import com.google.gwt.user.client.ui.Composite;
import com.google.gwt.user.client.ui.VerticalPanel;
import com.google.gwt.widgetideas.graphics.client.GWTCanvas;
import com.google.gwt.widgetideas.graphics.client.ImageLoader;

/**
 * Demo Showcasing simple image rendering, transformations and animations.
 */
public class LogoDemo extends SimpleCanvasDemo {

    /*
     * Controls for the logo demo. We dont actually have any controls at the
     * moment, so we just initialize with an empty Vertical Panel.
     */
    class LogoDemoControls extends Composite {
        public LogoDemoControls() {
            VerticalPanel layout = new VerticalPanel();
            initWidget(layout);
        }
    }

    /*
     * Reference to our ImageHandle that gets initialized on the callback from
     * ImageLoader.
     */
    private ImageElement img = null;

    private float rotation = 0.1f;

    /*
     * Animation timer.
     */
    private Timer timer;

    public LogoDemo(GWTCanvas theCanvas) {
        super(theCanvas);
        height = 400;
        width = 600;
        demoName = "GWT Logo";
    }

    public void createControls() {
        this.controls = new LogoDemoControls();
    }

    public void drawDemo() {
        // The following is the same as doing
        // canvas.resize(width,height);
        canvas.setCoordSize(width, height);
        canvas.setPixelHeight(height);
        canvas.setPixelWidth(width);

        String[] imageUrls = new String[] { "logo-185x175.png" };

        timer = new Timer() {

            @Override
            public void run() {
                renderingLoop();
            }

        };

        if (img == null) {
            // The first time this demo gets run we need to load our images.
            // Maintain a reference to the image we load so we can use it
            // the next time the demo is selected
            ImageLoader.loadImages(imageUrls, new ImageLoader.CallBack() {
                public void onImagesLoaded(ImageElement[] imageHandles) {
                    // Drawing code involving images goes here
                    img = imageHandles[0];
                    timer.schedule(10);
                }
            });

        } else {
            // Go ahead and animate
            if (isImageLoaded(img)) {
                timer.schedule(10);
            } else {
                Window.alert("Refresh the page to reload the image.");
            }
        }
    }

    public void stopDemo() {
        timer.cancel();
    }

    private native boolean isImageLoaded(ImageElement imgElem) /*-{
                                                               return !!imgElem.__isLoaded;
                                                               }-*/;

    private void renderingLoop() {
        canvas.saveContext();

        canvas.clear();
        // Draw a static version of the logo, sampling the last 100x100
        // (image is 185x175) pixels of the image.
        // Draw starting at position 10, 10
        // scaled up by a factor of 2 on the canvas (using 200x200 as the
        // destination dimensions).
        canvas.drawImage(img, 84, 74, 100, 100, 10, 10, 200, 200);

        // draw an animated version
        canvas.translate(300, 200);
        canvas.rotate(rotation);
        canvas.scale(.9f, .9f);

        canvas.drawImage(img, 0, 0);
        rotation += 0.1;

        canvas.restoreContext();
        timer.schedule(10);
    }
}