I wrote a little
applet game that my friends tell me runs well on Windows, but not on Mac.
Is there any software one can use to
test a
Java applet's compatibilty with various platforms?
What, if anything, tends to cause lack of cross-platform compatibility?
If you're feeling exceptionally generous, please see if you can spot the problem in the actual source code:
import java.awt.*;
import java.awt.event.*;
import java.applet.Applet;
public class TennisReturnGame extends Applet
{
Graphics offscreen ;
Image imageOffScreen ;
Button newGame;
Choice choice;
String scoreLine, instructions;
static String userscore = "0";
static String proscore = "0";
boolean started = false;
boolean isMoving = false;
boolean gameOver = false;
FontMetrics fm; // needed for centering message
int scoreLoc;
public void init()
{
setBackground( new Color( 0, 120, 0 ) );
setLayout( new BorderLayout( 3, 3 ) );
TennisCanvas court = new TennisCanvas( );
add( court, BorderLayout.CENTER );
Panel controlPanel = new Panel();
controlPanel.setBackground( new Color( 220, 200, 180 ) );
add( controlPanel, BorderLayout.SOUTH );
Panel topPanel = new Panel();
topPanel.setBackground( new Color( 220, 200, 180 ) );
add( topPanel, BorderLayout.NORTH );
fm = getFontMetrics( getFont() );
instructions = "Click once to activate. Spacebar initiates serve. Delays are built in.";
scoreLoc = 240 - ( fm.stringWidth( instructions )/2 );
newGame = new Button( "New Game" );
newGame.addActionListener( court );
newGame.setBackground( Color.lightGray );
topPanel.add( newGame );
choice = new Choice(); // user chooses opponent, which will determine ball speed
choice.addItem( "Greg Rusedski 149 mph" );
choice.addItem( "Venus Williams 127 mph" );
choice.addItem( "Conchita Martinez 98 mph" );
choice.addItem( "PeeWee Phenom 77 mph" );
choice.addItem( "Uncle Seymour 50 mph" );
choice.setBackground( Color.white );
controlPanel.add( new Label( " Opponent:" ) );
controlPanel.add( choice );
imageOffScreen = createImage( getSize().width, getSize().height );
offscreen = imageOffScreen.getGraphics();
court.proChoice = choice;
}
public Insets getInsets()
{
return new Insets( 3, 3, 3, 3 );
}
class TennisCanvas extends Canvas implements ActionListener, Runnable, KeyListener, MouseListener
{
double currX , currY ; // position of ball
double dy = ( Math.random()* 3 ) + 1; // change in ball's y position
double dx = 15;
int speed = 50;
int pointCount;
Thread animator;
Choice proChoice;
TennisCanvas() // constructor
{
setBackground( new Color( 0, 120, 0 ) );
currX = 84;
currY = 125;
addKeyListener( this );
addMouseListener( this );
animator = new Thread( this );
animator.start();
}
public int setSpeed() // speed based on opponenet chosen by user
{
int choiceIndex = proChoice.getSelectedIndex();
switch ( choiceIndex )
{
case 0:
return 75;
case 1:
return 64;
case 2:
return 49;
case 3:
return 39;
case 4:
return 25;
default:
return 50;
}
}
public void actionPerformed( ActionEvent evt ) // New Game button starts new game
{
String command = evt.getActionCommand();
if ( command.equals( "New Game" ) )
startNew();
}
public void startNew() // resets scores and starts new game
{
setBackground( new Color( 0, 120, 0 ) );
pointCount = 0;
isMoving = false;
started = false;
gameOver = false;
userscore = "0";
proscore = "0";
fm = getFontMetrics( getFont() );
scoreLine = "Opponent's score: " + proscore + " Your score: " + userscore;
instructions = "Click once to activate. Spacebar initiates serve.";
scoreLoc = 240 - ( fm.stringWidth( instructions )/2 );
repaint();
}
public void keyPressed( KeyEvent evt ) // hitting space bar initiates serve
{
int code = evt.getKeyCode();
if ( code == KeyEvent.VK_SPACE && isMoving == false && gameOver == false )
{
currX = 84;
if ( pointCount % 2 == 0 )
currY = 125;
else
currY = 110;
animator = new Thread( this );
animator.start();
}
}
public void mousePressed( MouseEvent evt ) // user tries to hit moving ball with mouse click
{
if ( started == false ) // first mouse click activates game but doesn't count as a "swing" at the ball
{
started = true;
newScore();
}
// if user clicks within 20 pixels of ball, user gets the point
else if ( evt.getX() > 324 && Math.abs( evt.getX() - ( currX + 5 ) ) <= 20 && ( Math.abs( evt.getY() - ( currY + 5 ) ) <= 20 ) )
{
dx = -dx;
dy = -dy;
addToUser();
}
else // otherwise, opponent gets the point
{
addToPro();
}
}
public void addToUser() // gives point to user
{
if ( gameOver == false && isMoving == true )
{
if ( userscore.equals( "0" ) )
userscore = "15";
else if ( userscore.equals( "15" ) )
userscore = "30";
else if ( userscore.equals( "30" ) )
userscore = "40";
else if ( userscore.equals( "40" ) ) // user wins game
{
userscore = "GAME!";
gameOver = true;
setBackground( new Color( 204, 102, 0 ) );
}
pointCount++;
newScore();
}
}
public void addToPro() // gives point to opponent
{
if ( isMoving == true && gameOver == false )
{
if ( proscore.equals( "0" ) )
proscore = "15";
else if ( proscore.equals( "15" ) )
proscore = "30";
else if ( proscore.equals( "30" ) )
proscore = "40";
else if ( proscore.equals( "40" ) ) // opponent wins game
{
proscore = "GAME!";
gameOver = true;
setBackground( new Color( 204, 102, 0 ) );
}
pointCount++;
newScore();
}
}
public void newScore() // updates score
{
scoreLine = "Opponent's score: " + proscore + " Your score: " + userscore;
fm = getFontMetrics( getFont() );
scoreLoc = 240 - ( fm.stringWidth( scoreLine )/2 );
repaint();
}
public void run()
{
isMoving = true;
speed = setSpeed();
int cycles = 7000/speed;
dx = ( 15 * speed ) / 100;
double rand = ( Math.random()* 10 ) + 5;
if ( pointCount % 2 == 0 )
dy = -dx/rand;
else
dy = dx/rand;
for ( int i = 0 ; i <= 100 ; i++ ) // delay keeps ball still for a few seconds
{
try
{
Thread.sleep( 10 );
}
catch ( InterruptedException e )
{
}
repaint();
}
for ( int i = 0 ; i <= cycles ; i++ ) // moves ball across tennis court
{
try
{
Thread.sleep( 10 );
}
catch ( InterruptedException e )
{
}
// update the x and y coordinates for the ball
currX = currX + dx;
currY = currY + dy;
repaint();
} //close for loop
isMoving = false;
} //close run
public void update( Graphics g )
{
paint( g );
}
public void paint( Graphics g )
{
offscreen.setColor( getBackground() );
offscreen.fillRect( 0, 0, getSize().width, getSize().height );
offscreen.setColor ( Color.yellow );
offscreen.fillOval( (int)currX , (int)currY , 10, 10 );
offscreen.setColor ( Color.white );
offscreen.drawRect( 84, 66, 312, 108 );
offscreen.drawLine( 240, 66, 240, 174 );
offscreen.drawLine( 156, 120, 324, 120 );
offscreen.drawLine( 156, 66, 156, 174 );
offscreen.drawLine( 324, 66, 324, 174 );
offscreen.setColor( Color.green );
if ( started == true )
offscreen.drawString( scoreLine, scoreLoc, 20 );
else
offscreen.drawString( instructions, scoreLoc, 20 );
g.drawImage( imageOffScreen , 0 , 0 , this );
} // close paint
public void mouseEntered( MouseEvent evt ) { }
public void mouseExited( MouseEvent evt ) { }
public void mouseReleased( MouseEvent evt ) { }
public void mouseClicked( MouseEvent evt ) { }
public void keyTyped( KeyEvent evt ) { }
public void keyReleased( KeyEvent evt ) { }
} // close TennisCanvas
}