The Bounce class; create and start Sprites, using Threads Java code example - Click here to copy ->>>

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<TITLE>A Bounce of a Demo</TITLE>

<BODY BGCOLOR=Yellow>

<H1>A Bounce of a Demo</H1>

<APPLET CODE="Bounce" WIDTH=300 HEIGHT=200>

</APPLET>

</BODY>

/*
* Copyright (c) Ian F. Darwin, http://www.darwinsys.com/, 1996-2002.
* All rights reserved. Software written by Ian F. Darwin and others.
* $Id: LICENSE,v 1.8 2004/02/09 03:33:38 ian Exp $
*/

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

/** This is the Bounce class; create and start Sprites, using Threads. */
public class Bounce extends Applet implements ActionListener {
  /** The main Panel */
  protected Panel p;
  /** The image, shared by all the Sprite objects */
  protected Image img;
  /** A Vector of Sprite objects. */
  protected Vector v;

    public void init() {
    Button b = new Button("Start");
    b.addActionListener(this);
    setLayout(new BorderLayout());
    add(b, BorderLayout.NORTH);
    add(p = new Panel(), BorderLayout.CENTER);
    p.setLayout(null);
    String imgName = getParameter("imagefile");
    if (imgName == null) imgName = "duke.gif";
    img = getImage(getCodeBase(), imgName);
    MediaTracker mt = new MediaTracker(this);
    mt.addImage(img, 0);
    try {
      mt.waitForID(0);
    } catch(InterruptedException e) {
      throw new IllegalArgumentException(
        "InterruptedException while loading image " + imgName);
    }
    if (mt.isErrorID(0)) {
      throw new IllegalArgumentException(
        "Couldn't load image " + imgName);
    }
    v = new Vector();
    }

    public void actionPerformed(ActionEvent e) {
    System.out.println("Creat-ing another one!");
    Sprite s = new Sprite(this, img);
    s.start();
    p.add(s);
    v.addElement(s);
    }

    public void stop() {
    for (int i=0; i<v.size(); i++) {
      ((Sprite)(v.get(i))).stop();
    }
    v.clear();
    }
}

/**
* Java Code from Java Cookbook, Second Edition
* By Ian F. Darwin
* Second Edition June 2004
* Series: Cookbooks
* ISBN: 0-596-00701-9
* Details: http://www.oreilly.com/catalog/javacook2/index.html
* Copyright (c) Ian F. Darwin, http://www.darwinsys.com/, 1996-2002.
* All rights reserved. Software written by Ian F. Darwin and others.
* $Id: LICENSE,v 1.8 2004/02/09 03:33:38 ian Exp $
*/

/*
* Copyright (c) Ian F. Darwin, http://www.darwinsys.com/, 1996-2002.
* All rights reserved. Software written by Ian F. Darwin and others.
* $Id: LICENSE,v 1.8 2004/02/09 03:33:38 ian Exp $
*/

import java.awt.*;

/** A Sprite is one Image that moves around the screen on its own */
public class Sprite extends Component implements Runnable {
  protected static int spriteNumber = 0;
  protected Thread t;
  protected int x, y;
  protected Component parent;
  protected Image img;
  protected boolean done = false;
  /** The time in mSec to pause between each move. */
  protected int sleepTime = 250;
  /** The direction for this particular sprite. */
  protected int direction;
  /** The direction for going across the page */
  public static final int HORIZONTAL = 1;
  /** The direction for going up and down */
  public static final int VERTICAL = 2;
  /** The direction for moving diagonally */
  public static final int DIAGONAL = 3;

  /** Construct a Sprite with a Component parent, image and direction.
   * Construct and start a Thread to drive this Sprite.
   */
  public Sprite(Component parent, Image img, int dir) {
    super();
    this.parent = parent;
    this.img = img;
    switch(dir) {
      case VERTICAL: case HORIZONTAL: case DIAGONAL:
        direction = dir;
        break;
      default:
        throw new IllegalArgumentException(
          "Direction " + dir + " invalid");
    }
    setSize(img.getWidth(this), img.getHeight(this));
  }

  /** Construct a sprite with the default direction */
  public Sprite(Component parent, Image img) {
    this(parent, img, DIAGONAL);
  }

  /** Start this Sprite's thread. */
  public void start() {
    t = new Thread(this);
    t.setName("Sprite #" + ++spriteNumber);
    t.start();
  }

  /** Stop this Sprite's thread. */
  public void stop() {
    if (t == null)
      return;
    System.out.println("Stopping " + t.getName());
    done = true;
  }

  /** Adjust the motion rate */
  protected void setSleepTime(int n) {
    sleepTime = n;
  }

  /**
   * Run one Sprite around the screen.
   * This version just moves them around either across, down, or
   * at some 45-degree angle.
   */
    public void run() {
    int width = parent.getSize().width;
    int height = parent.getSize().height;
    // Set initial location
    x = (int)(Math.random() * width);
    y = (int)(Math.random() * height);
    // Flip coin for x & y directions
    int xincr = Math.random()>0.5?1:-1;
    int yincr = Math.random()>0.5?1:-1;
    while (!done) {
      width = parent.getSize().width;
      height = parent.getSize().height;
      if ((x+=xincr) >= width)
        x=0;
      if ((y+=yincr) >= height)
        y=0;
      if (x<0)
        x = width;
      if (y<0)
        y = height;
      switch(direction) {
        case VERTICAL:
          x = 0;
          break;
        case HORIZONTAL:
          y = 0;
          break;
        case DIAGONAL: break;
      }
      //System.out.println("from " + getLocation() + "->" + x + "," + y);
      setLocation(x, y);
      repaint();
      try {
        Thread.sleep(sleepTime);
      } catch (InterruptedException e) {
        return;
      }
    }
  }

  /** paint -- just draw our image at its current location */
    public void paint(Graphics g) {
    g.drawImage(img, 0, 0, this);
    }
}