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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=217-223//-->
<!--UNASSIGNED1//-->
<!--UNASSIGNED2//-->
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<P><B>Listing 6-2</B> GunManager class</P>
<!-- CODE //-->
<PRE>
/////////////////////////////////////////////////////////////////
public class GunManager {
private GunSprite gun; // your gun
private int gun_width; // width of gun
private int gun_height;
private MissileSprite missile; // missile
private int min_x,max_x; // min and max x coords
// for gun movement
private int gun_min_x,gun_max_x;
private int mis_min_x,mis_max_x;
private int gun_y;
private boolean displayHit;
private int energy;
private int maxEnergy;
private int energyDec;
private GameManager game; // ptr to game manager
static int width, height; // applet dimensions
static final int ENERGY_PER_HIT = 5; // energy used per hit
static final int MISSILE_WIDTH = 3;
static final int MISSILE_HEIGHT = 27;
static final int MISSILE_SPEED = -27; // missile flies upward
static final Color MISSILE_COLOR= Color.red;
public GunManager(int maxEnergy,int energyDec,int width,int height,
Image gunImage,Intersect target[],Applet a) {
this.maxEnergy = maxEnergy;
this.energyDec = energyDec;
this.width = width;
this.height = height;
gun = new GunSprite(gunImage,a,this);
gun_width = gunImage.getWidth(a)/2;
gun_height = gunImage.getHeight(a);
gun_y = height - gun_height;
min_x = gun_width;
max_x = width - gun_width;
gun_min_x = 0;
gun_max_x = width - 2*gun_width;
mis_min_x = min_x-2;
mis_max_x = max_x-2;
gun.setPosition(width/2-gun_width,gun_y);
missile = new MissileSprite(MISSILE_WIDTH,MISSILE_HEIGHT,
MISSILE_COLOR,MISSILE_SPEED,
height-gun_height+13,
0,target);
game = (GameManager)a; // set ptr to GameManager
}
// set parameters for the new game
public void newGame() {
gun.setPosition(width/2-gun_width,gun_y);
gun.restore();
displayHit = false;
energy = maxEnergy;
}
// move gun to the given x coordinate
public void moveGun(int x) {
if (x <= min_x) {
gun.setPosition(gun_min_x,gun_y);
}
else if (x >= max_x) {
gun.setPosition(gun_max_x,gun_y);
}
else {
gun.setPosition(x-gun_width,gun_y);
}
}
// fire missile from given x coordinate
public void fireMissile(int x) {
if (!missile.isActive()) { // if missile sprite
// isn't active
if (x <= min_x) {
missile.init(mis_min_x);
}
else if (x >= max_x) {
missile.init(mis_max_x);
}
else {
missile.init(x-1); // initialize missile
}
}
}
// update all the parameters associated with the
// gun. In this case, only the missile needs to move
// automatically.
public void update() {
missile.update();
}
// paint all sprites associated with gun
// also paint status display for amount of energy left
String energyString = "Energy";
public void paint(Graphics g) {
// if gun is hit, flash a red rectangle
// instead of painting gun
if (displayHit) {
g.setColor(Color.red);
g.fillRect(0,gun_y,width,gun_height);
displayHit = false;
}
else {
gun.paint(g);
}
missile.paint(g);
// display energy left
g.setColor(Color.red);
g.drawString(energyString,3,13);
g.fillRect(0,17,energy,10);
}
// accessor function for gun
public GunSprite getGun() {
return gun;
}
// get the y-coordinate of the gun
public int getGunY() {
return gun_y;
}
// handles a hit from an alien
public void handleHit() {
displayHit = true; // set display hit flag
energy -= energyDec; // update energy
if (energy <= 0) { // game over if energy <= 0
game.gameOver(); // notify game manager
gun.suspend(); // turn off sprites
missile.suspend();
}
}
// set the amount of energy lost per hit (energy decrement)
public void setEnergyDec(int dec) {
energyDec = dec;
}
}
</PRE>
<!-- END CODE //-->
<P><B>Listing 6-3</B> UFOManager class</P>
<!-- CODE //-->
<PRE>
/////////////////////////////////////////////////////////////////
public class UFOManager {
private UFO ufo[]; // array of ufos
int ufosKilled; // count ufos killed
int level; // the level
// (i.e. #ufos on screen)
int startLevel;
int maxLevel;
boolean playSound = false; // initially no sound
AudioClip expsound; // sound clip of explosion
// kill 13 ufos until next level
static final int KILL_FOR_NEXT_LEVEL = 13;
static int width, height; // applet dimensions
// constructor
public UFOManager(int startLevel,int maxLevel,int width,int height,
Image ufoImages[],
Image attackImages[],
Image explodeImages[],
Applet a, AudioClip exp) {
this.startLevel = startLevel;
this.maxLevel = maxLevel;
this.width = width;
this.height = height;
ufo = new UFO[maxLevel];
for (int i=0; i<ufo.length; i++) {
ufo[i] = new UFO(ufoImages,attackImages,explodeImages,
width,height,this,a);
}
expsound = exp;
newGame();
}
// allow the UFO class to communicate with the gun
public void initialize(GunManager gm) {
UFO.initialize(gm);
}
// set ufo at a random screen location
private void initializePosition(Moveable m) {
m.setPosition(UFO.getRand(width - 100)+50,
UFO.getRand(height - 150)+31);
}
// initialize parameters of new Game
public void newGame() {
ufosKilled = 0;
level = startLevel; // start with startLevel ufos
// on the screen
for (int i=0; i<ufo.length; i++) {
initializePosition(ufo[i]);
if (i >= level) { // suspend ufos
// above start level
ufo[i].suspend();
}
}
}
// return array of ufos
public UFO[] getUFO() {
return ufo;
}
// paint all ufos in a level
public void paint(Graphics g) {
for (int i=0; i<level; i++) {
ufo[i].paint(g);
}
}
// update all ufos in a level. Otherwise start
// ufo if it's not on screen
public void update() {
for (int i=0; i<level; i++) {
if (ufo[i].isActive()) {
ufo[i].update();
}
else { // make new ufo
initializePosition(ufo[i]);
ufo[i].init();
}
}
}
// tracks the number of ufos killed. If the
// num_killed is divisible by KILL_FOR_NEXT_LEVEL
// increment the level
public void killed() {
ufosKilled++;
if (ufosKilled % KILL_FOR_NEXT_LEVEL == 0) {
level = (level == maxLevel) ? maxLevel : level+1;
}
}
public void setStartLevel(int start) {
startLevel = start;
}
public void setSound(boolean s) {
playSound = s;
}
public void playExplosion() {
if (playSound && expsound != null) {
expsound.play();
}
}
}
</PRE>
<!-- END CODE //-->
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