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<META name=vsisbn content="1571690433"><META name=vstitle content="Black Art of Java Game Programming"><META name=vsauthor content="Joel Fan"><META name=vsimprint content="Sams"><META name=vspublisher content="Macmillan Computer Publishing"><META name=vspubdate content="11/01/96"><META name=vscategory content="Web and Software Development: Programming, Scripting, and Markup Languages: Java"><TITLE>Black Art of Java Game Programming:Extending Your Video Game</TITLE>
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<font face="arial, helvetica" size="-1" color="#336633"><b>Black Art of Java Game Programming</b></font>
<br>
<font face="arial, helvetica" size="-1"><i>by Joel Fan</i>
<br>
Sams, Macmillan Computer Publishing
<br>
<b>ISBN:</b> 1571690433<b> Pub Date:</b> 11/01/96</font>
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<!--ISBN=1571690433//-->
<!--TITLE=Black Art of Java Game Programming//-->
<!--AUTHOR=Joel Fan//-->
<!--AUTHOR=Eric Ries//-->
<!--AUTHOR=Calin Tenitchi//-->
<!--PUBLISHER=Macmillan Computer Publishing//-->
<!--IMPRINT=Sams//-->
<!--CHAPTER=6//-->
<!--PAGES=211-217//-->
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<H3><A NAME="Heading9"></A><FONT COLOR="#000077">Source Code for Modified Classes</FONT></H3>
<P>Listings 6-1 through 6-5 show the source of the classes we’ve modified in this chapter: GameManager, GunManager, UFOManager, GunSprite, and UFO.
</P>
<P><B>Listing 6-1</B> GameManager class</P>
<!-- CODE //-->
<PRE>
import java.applet.*;
import java.awt.*;
/////////////////////////////////////////////////////////////////
public class GameManager extends Applet
implements Runnable {
// animation variables
static final int REFRESH_RATE = 80; // in ms
Thread animation;
Graphics offscreen;
Image image;
// game variables used when playing
static final int UFO_VALUE = 130; // 130 points
static final int MAX_LANDED = 5; // at most 5 aliens
// can land
static final int MAX_LEVEL = 9; //
static final int MAX_ENERGY = 113; //
private int score;
private int numLanded; // num of aliens landed
Image ufoImages[] = new Image[6]; // 6 ufo Images
Image attackImages[] = new Image[6]; // 6 attack Images
Image explodeImages[] = new Image[4];// 4 explode Images
Image gunImage; // gun image
GunManager gm; // refers to gun manager
UFOManager um; // refers to ufo manager
// state of game
private boolean playing; // if game playing
private int screen; // which screen to show
static final int INTRO = 0; // intro screen
static final int GAME_OVER = 1; // game over screen
AudioClip expsound; // explosion sound
// fonts
Font smallFont = new Font("Helvetica",Font.BOLD,12);
Font mediumFont = new Font("Helvetica",Font.BOLD,14);
Font bigFont = new Font("Helvetica",Font.BOLD,18);
FontMetrics fm; // use to center string
int width, height; // applet dimensions
// strings
String scoreString = "Score: ";
String ufoLandedString = "UFOs Landed: ";
String gameOverString = " GAME OVER ";
String clickString = "Shift-Click to Continue";
String alienLandingString = "Alien Landing";
int stringWidth;
String introString[] = new String[8];
public void init() {
showStatus(“Loading Images -- WAIT!”);
setBackground(Color.black); // applet background
width = bounds().width; // set applet dimensions
height = bounds().height;
loadImages();
try {
expsound = getAudioClip(getCodeBase(),"Explosion.au");
}
catch (Exception e) { }
um = new UFOManager(2,MAX_LEVEL,width,height,ufoImages,
attackImages,explodeImages,
this,expsound);
gm = new GunManager(MAX_ENERGY,5,width,height,gunImage,
um.getUFO(),
this);
um.initialize(gm); // initialize gun parameters
playing = false; // not playing
screen = INTRO; // show intro screen
image = createImage(width,height); // make offscreen buffer
offscreen = image.getGraphics();
offscreen.setFont(bigFont); // font for intro
fm = offscreen.getFontMetrics(bigFont); // font metrics
stringWidth = fm.stringWidth(alienLandingString);
introString[0] = "You are Humanity's last hope!";
introString[1] = "Destroy the green Alien Landers";
introString[2] = "by using the Mouse to Move";
introString[3] = "your Missile Launcher. Click";
introString[4] = "to Fire Missile. If 5 Aliens";
introString[5] = "Land, or Energy Runs Out,";
introString[6] = "Humans will be Eaten Alive!";
introString[7] = "Click to start Game";
}
// load all images used in game
public void loadImages() {
MediaTracker t = new MediaTracker(this);
gunImage = getImage(getCodeBase(),"image/gun.gif");
t.addImage(gunImage,0);
for (int i=0; i<ufoImages.length; i++) {
ufoImages[i] = getImage(getCodeBase(),
"image/ufo" + i + ".gif");
t.addImage(ufoImages[i],0);
attackImages[i] = getImage(getCodeBase(),
"image/attack" + i + ".gif");
t.addImage(attackImages[i],0);
}
for (int i=0; i<explodeImages.length; i++) {
explodeImages[i] = getImage(getCodeBase(),
"image/explode" + i + ".gif");
t.addImage(explodeImages[i],0);
}
// wait for all images to finish loading //
try {
t.waitForAll();
} catch (InterruptedException e) {
}
// check for errors //
if (t.isErrorAny()) {
showStatus("Error Loading Images");
}
else if (t.checkAll()) {
showStatus("Images successfully loaded");
}
}
// initialize params for new game
public void newGame() {
score = 0; // no score
numLanded = 0; // no aliens landed
gm.newGame(); // call newGame in
um.newGame(); // manager classes
offscreen.setFont(smallFont); // set font in game
}
// handle mouse events //
public boolean mouseMove(Event e,int x,int y) {
if (playing) {
gm.moveGun(x);
}
return true;
}
public boolean mouseDrag(Event e,int x,int y) {
if (playing) {
gm.moveGun(x);
}
return true;
}
public boolean mouseDown(Event e,int x,int y) {
if (playing) {
gm.fireMissile(x);
}
else if (screen == INTRO) { // start game for mouse
// down on intro screen
playing = true;
newGame();
}
else if (screen == GAME_OVER) { // else go back to intro
if (e.shiftDown()) { // if shift-click
screen = INTRO;
}
}
return true;
}
// start the Video Game Loop
public void start() {
showStatus(“Starting Game!”);
animation = new Thread(this);
if (animation != null) {
animation.start();
}
}
// update managers. only update gun if playing
public void updateManagers() {
if (playing) {
gm.update();
}
um.update();
}
// override update so it doesn't erase screen
public void update(Graphics g) {
paint(g);
}
// paint the applet depending on mode of game
public void paint(Graphics g) {
if (playing) {
offscreen.setColor(Color.black);
offscreen.fillRect(0,0,width,height); // clear buffer
// draw status info
offscreen.setColor(Color.cyan);
offscreen.drawString(scoreString+score,width - 113,13);
offscreen.drawString(ufoLandedString+numLanded,
width - 113,27);
// tell UFOManager and GunManager to paint
um.paint(offscreen);
gm.paint(offscreen);
g.drawImage(image,0,0,this);
}
else if (screen == INTRO) {
offscreen.setColor(Color.black);
offscreen.fillRect(0,0,width,height); // clear buffer
offscreen.setFont(smallFont);
offscreen.setColor(Color.cyan);
offscreen.drawString(scoreString+score,width - 113,13);
offscreen.drawString(ufoLandedString+numLanded,
width - 113,27);
um.paint(offscreen);
offscreen.setFont(bigFont);
offscreen.setColor(Color.green);
offscreen.drawString(alienLandingString,
(width-stringWidth)/2,
height/6);
offscreen.setColor(Color.magenta);
offscreen.setFont(mediumFont);
// draw instructions
for (int i=0; i<introString.length-1; i++) {
offscreen.drawString(introString[i],13,(3+i)*height/12);
}
offscreen.setColor(Color.green);
offscreen.drawString(introString[7],
(width-stringWidth)/2,
height*11/12);
g.drawImage(image,0,0,this);
}
else if (screen == GAME_OVER) {
offscreen.setColor(Color.black);
offscreen.fillRect(0,0,width,height); // clear buffer
// draw status info
offscreen.setFont(smallFont);
offscreen.setColor(Color.cyan);
offscreen.drawString(scoreString+score,width - 113,13);
offscreen.drawString(ufoLandedString+numLanded,
width - 113,27);
um.paint(offscreen);
gm.paint(offscreen);
offscreen.setFont(bigFont);
offscreen.setColor(Color.red);
offscreen.drawString(gameOverString,
(width-stringWidth)/2,
height/2);
offscreen.setFont(mediumFont);
offscreen.setColor(Color.green);
offscreen.drawString(clickString,
(width-stringWidth-17)/2,
height*11/12);
g.drawImage(image,0,0,this);
}
}
// the Video Game Loop
public void run() {
while (true) {
repaint();
updateManagers();
Thread.currentThread().yield();
try {
Thread.sleep (REFRESH_RATE);
} catch (Exception exc) { };
}
}
// stop animation
public void stop() {
showStatus("Game Stopped");
if (animation != null) {
animation.stop();
animation = null;
}
}
// increase score
public void incrementScore() {
score += UFO_VALUE;
}
// count number of ufo's landed
public void alienLanded() {
numLanded++;
if (numLanded == MAX_LANDED) {
gameOver();
}
}
// handle game over
public void gameOver() {
if (playing) {
playing = false;
screen = GAME_OVER;
}
}
}
</PRE>
<!-- END CODE //-->
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