Java 1.2 How-To/JavaHowTo.iso/javafile/ch07/Advertiser.java

Java Source | 1998-12-14 | 6.7 KB | 317 lines

import java.util.*;
import java.awt.*;
import java.applet.Applet;

/*
 * A class that performs the banner animation
 */
class Banner extends Panel implements Runnable {

/*
 * an instance of the applet for
 * invoking methods from the Advertiser class
 */
Advertiser advertiser;

/*
 * instance of thread used for animation
 */
Thread thread;

/*
 * the next banner image to be displayed
 */
Image theImage;

/*
 * width and height of the new banner image
 */
int img_width, img_height;

/*
 * offscreen image for double-buffering
 */
Image offscreen;

/*
 * offg1 is the graphics object associated with
 * offscreen image. offg2 is the clipped version
 * of offg1
 */
Graphics offg1, offg2;

/*
 * xstart, ystart - x and y coordinate of clipping rectangle
 * width, height - width and height of clipping rectangle
 * effect_type - the effect type applied to the next image
 */
int xstart, ystart, width, height, effect_type;

/**
 * constructor just saves instance of the applet
 * @param advertiser - instance of advertiser applet
 */
Banner (Advertiser advertiser) {

    this.advertiser = advertiser;
}

/*
 * thread that calls repaint() every 25ms
 * to effect animation
 */
public void run() {

    Dimension d = getSize();
    offscreen = createImage (d.width, d.height);
    offg1 = offscreen.getGraphics ();
    offg1.setFont (getFont ());
    offg1.setColor (Color.gray);
    offg1.fillRect (0, 0, d.width, d.height);
    while (true) {
        repaint ();
        try {
            Thread.sleep (25);
        } catch (InterruptedException e) {
            break;
        }
    }
}

/**
 * override update() method to avoid erase flicker
 * this is where the drawing is done
 * @param g - destination graphics object
 */
public synchronized void update(Graphics g) {

    int i, x, y, w, h;
    switch (effect_type) {
        case 0:
        offg1.drawImage (theImage, 0, 0, null);
        break;

        case 1:        // barn-door open
        if (xstart > 0) {
            xstart -= 5;
            width += 10;
            offg2 = offg1.create (xstart, 0, width, height);
            offg2.drawImage (theImage, -xstart, 0, null);
        } else offg1.drawImage (theImage, 0, 0, null);
        break;

        case 2:        // venetian blind
        if (height < 10) {
            height += 1;
            for (y=0; y<img_height; y+=10) {
                offg2 = offg1.create (0, y, width, height);
                offg2.drawImage (theImage, 0, -y, null);
            }
        } else offg1.drawImage (theImage, 0, 0, null);
        break;

        case 3:        // checkerboard
        if (width <= 20) {
            if (width <= 10) {
                i = 0;
                for (y=0; y<img_height; y+=10) {
                    for (x=(i&1)*10; x<img_width; x+=20) {
                        offg2 = offg1.create (x, y, width, 10);
                        offg2.drawImage (theImage, -x, -y,σ
 null);
                    }
                    i += 1;
                }
            } else {
                i = 1;
                for (y=0; y<img_height; y+=10) {
                    for (x=(i&1)*10; x<img_width; x+=20) {
                        offg2 = offg1.create (x, y,[cc]
 width-10, 10);
                        offg2.drawImage (theImage,σ
 -x, -y, null);
                    }
                    i += 1;
                }
            }
            width += 5;
        } else offg1.drawImage (theImage, 0, 0, null);
        break;
    }
    g.drawImage (offscreen, 0, 0, null);
}

/**
 * initialize variables for clipping rectangle
 * depending on effect type
 * @param which - the effect type for next image
 * @param img - the next image
 */
public void effect (int which, Image img) {

    img_width = img.getWidth (null);
    img_height = img.getHeight (null);
    theImage = img;
    switch (which) {
        case 0:
        break;

        case 1:        // barn door
        xstart = img_width >> 1;
        width = 0;
        height = img_height;
        break;

        case 2:
        width = img_width;
        height = 0;
        break;

        case 3:
        width = 0;
        break;
    }
    effect_type = which;
}

/*
 * start the repaint thread
 */
public void start() {

    thread = new Thread(this);
    thread.start();
}

/*
 * stop the repaint thread
 */
public void stop() {

    if (thread != null)
        thread = null;
}
}

/*
 * the Advertiser class proper
 */
public class Advertiser extends Applet implements Runnable {

/*
 * instance of Banner
 */
Banner panel;

/*
 * instance of thread for cycling effects
 * for each new image
 */
Thread thread;

/*
 * the total number of images
 */
int NBanners;

/*
 * the array of images
 */
Image img[] = new Image[10];

/*
 * the delay (dwell) time in milliseconds for each image
 */
int delay[] = new int[10];

/*
 * the effect type for each image
 */
int effect[] = new int[10];

/*
 * called when applet is loaded
 * add the banner panel, load images, and parse applet
 * parameters
 */
public void init() {

    int i;
    setLayout(new BorderLayout());

    panel = new Banner (this);
    add("Center", panel);
    NBanners = 0;
    MediaTracker tracker = new MediaTracker (this);

    for (i=1; i<=10; i+=1) {
        String param, token;
        int j, next;

        param = getParameter ("T"+i);
        if (param == null) break;

        StringTokenizer st = new StringTokenizer (param, " ,");

        token = st.nextToken ();
        img[NBanners] = getImage (getDocumentBase(), token);
        tracker.addImage (img[NBanners], i);
        showStatus ("Getting image: "+token);
        try {
            tracker.waitForID (i);
        } catch (InterruptedException e) { }

        token = st.nextToken ();
        delay[NBanners] = Integer.parseInt (token);

        token = st.nextToken ();
        effect[NBanners] = Integer.parseInt (token);

        NBanners += 1;
    }
}

/*
 * thread that starts the next image transition
 */
public void run () {

    int current = 0;

    while (true) {
        panel.effect (effect[current], img[current]);
        try {
            Thread.sleep (delay[current]);
        } catch (InterruptedException e) { }
        current += 1;
        current %= NBanners;
    }
}

/*
 * called when applet is started
 * start both threads
 */
public void start() {

    panel.start();
    thread = new Thread(this);
    thread.start();
}

/*
 * called when applet is stopped
 * stops all threads
 */
public void stop() {

    panel.stop();

    if (panel != null)
        panel = null;

    if (thread != null)
        thread = null;
}
}