Java Developer's Companion/Java Developer's Companion.iso/documentation/tutorial/ui/drawing/example/MTImageSequence.java

Java Source | 1997-07-13 | 5.2 KB | 171 lines

/*
 * Copyright (c) 1995-1997 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Permission to use, copy, modify, and distribute this software
 * and its documentation for NON-COMMERCIAL purposes and without
 * fee is hereby granted provided that this copyright notice
 * appears in all copies. Please refer to the file "copyright.html"
 * for further important copyright and licensing information.
 *
 * SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF
 * THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
 * TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR
 * ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR
 * DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES.
 */
import java.awt.*;
import java.applet.Applet;

/*
 * This applet displays several images in a row.  It prevents
 * flashing by double buffering.  MediaTracker preloads the image
 * data using multiple background threads.  The program doesn't
 * draw until all the images are fully loaded.
 */

public class MTImageSequence extends Applet implements Runnable {
    int frameNumber = -1;
    int delay;
    Thread animatorThread;
    boolean frozen = false;

    Dimension offDimension;
    Image offImage;
    Graphics offGraphics;

    Image[] images;
    MediaTracker tracker;

    public void init() {
        String str;
        int fps = 10;

        //How many milliseconds between frames?
        str = getParameter("fps");
        try {
            if (str != null) {
                fps = Integer.parseInt(str);
            }
        } catch (Exception e) {}
        delay = (fps > 0) ? (1000 / fps) : 100;

        //Load all the images.
        images = new Image[10];
        tracker = new MediaTracker(this);
        for (int i = 1; i <= 10; i++) {
            images[i-1] = getImage(getCodeBase(),
                          "../../../images/duke/T"+i+".gif");
            tracker.addImage(images[i-1], 0);
        }
    }

    public void start() {
        if (frozen) {
            //Do nothing.  The user has requested that we
            //stop changing the image.
        } else {
            //Start animating!
            if (animatorThread == null) {
                animatorThread = new Thread(this);
            }
            animatorThread.start();
        }
    }

    public void stop() {
        //Stop the animating thread.
        animatorThread = null;

        //Get rid of the objects necessary for double buffering.
        offGraphics = null;
        offImage = null;
    }

    public boolean mouseDown(Event e, int x, int y) {
        if (frozen) {
            frozen = false;
            start();
        } else {
            frozen = true;

            //Instead of calling stop(), which destroys the
            //backbuffer, just stop the animating thread.
            animatorThread = null;
        }
        return true;
    }

    public void run() {
        try {
            //Start downloading the images. Wait until they're loaded
        //before requesting repaints.
            tracker.waitForAll();
        } catch (InterruptedException e) {}

        //Just to be nice, lower this thread's priority
        //so it can't interfere with other processing going on.
        Thread.currentThread().setPriority(Thread.MIN_PRIORITY);

        //Remember the starting time.
        long startTime = System.currentTimeMillis();

        //This is the animation loop.
        while (Thread.currentThread() == animatorThread) {
            //Advance the animation frame.
            frameNumber++;

            //Display it.
            repaint();

            //Delay depending on how far we are behind.
            try {
                startTime += delay;
                Thread.sleep(Math.max(0,
                                      startTime-System.currentTimeMillis()));
            } catch (InterruptedException e) {
                break;
            }
        }
    }

    public void paint(Graphics g) {
        update(g);
    }

    public void update(Graphics g) {
        Dimension d = size();

        //If not all the images are loaded, just clear the background
        //and display a status string.
        if (!tracker.checkAll()) {
            g.clearRect(0, 0, d.width, d.height);
            g.drawString("Please wait...", 0, d.height/2);
        }

        //If all images are loaded, draw.
        else {

            //Create the offscreen graphics context, if no good one exists.
            if ( (offGraphics == null)
              || (d.width != offDimension.width)
              || (d.height != offDimension.height) ) {
                offDimension = d;
                offImage = createImage(d.width, d.height);
                offGraphics = offImage.getGraphics();
            }

            //Erase the previous image.
            offGraphics.setColor(getBackground());
            offGraphics.fillRect(0, 0, d.width, d.height);
            offGraphics.setColor(Color.black);

            //Paint the frame into the image.
            offGraphics.drawImage(images[frameNumber % 10], 0, 0, this);

            //Paint the image onto the screen.
            g.drawImage(offImage, 0, 0, this);
        }
    }
}