I’ve just started Java and we have been asked to produce pong (or a twist on it). I am currently working on the collision between the ball and the players bat. I’ve got this code.
Rectangle2D.Double player;
Ellipse2D.Double ball;
public void drawActualPicture( Graphics2D g )
{
// Players Bat
g.setPaint( Color.green ); // Paint Colour
player = new Rectangle2D.Double( playerX, playerY, PW, PH );
g.fill(player);
// The ball at the current x, y position (width, height)
g.setPaint( Color.red );
ball = new Ellipse2D.Double( x-HALF_BALL_SIZE, y-HALF_BALL_SIZE, BALL_SIZE, BALL_SIZE );
g.fill( ball );
}
Some irrelevant code has been removed.
Then to detect my collision I’ve used
if ( ball.getBounds2D() == player.getBounds2D() )
{
System.out.println("true");
//x_inc = -1*ballS;
}
When the code is used the game simple freezes. When commented out the game runs fine.
Any ideas? Am I using the correct method in the correct way? Would it be better to use intersects?
Thanks
EDIT: It appears that anything involving .getBounds2D(); causes the game to crash. Any ideas?
EDIT2: Adding all of code-completly not needed parts
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.awt.image.*;
import javax.swing.JFrame;
import javax.swing.JPanel;
/*
* Note If you change S (Speed) collision detection will be more complex
* as the ball edge may be within the bat.
* Ignores concurrency issues (x,y access)
*/
class Main
{
public static void main( String args[] ) //
{ //
System.out.println("Application");
Application app = new Application();
app.setVisible(true);
app.run();
} //
}
class Application extends JFrame // So graphical
{
private static final int H = 600; // Height of window
private static final int W = 800; // Width of window
public Application()
{
setSize( W, H ); // Size of application
addKeyListener( new Transaction() ); // Called when key press
setDefaultCloseOperation(EXIT_ON_CLOSE);
}
public void update( Graphics g ) // Called by repaint
{ //
drawPicture( (Graphics2D) g ); // Draw Picture
}
public void paint( Graphics g ) // When 'Window' is first
{ // shown or damaged
drawPicture( (Graphics2D) g ); // Draw Picture
}
private Dimension theAD; // Alternate Dimension
private BufferedImage theAI; // Alternate Image
private Graphics2D theAG; // Alternate Graphics
public void drawPicture( Graphics2D g ) // Double buffer
{ // allow re-size
Dimension d = getSize(); // Size of curr. image
if ( ( theAG == null ) ||
( d.width != theAD.width ) ||
( d.height != theAD.height ) )
{ // New size
theAD = d;
theAI = (BufferedImage) createImage( d.width, d.height );
theAG = theAI.createGraphics();
AffineTransform at = new AffineTransform();
at.setToIdentity();
at.scale( ((double)d.width)/W, ((double)d.height)/H );
theAG.transform(at);
}
drawActualPicture( theAG ); // Draw Actual Picture
g.drawImage( theAI, 0, 0, this ); // Display on screen
}
// The ball position and how to increment to next position
private int x = W/2, x_inc = 1;
private int y = H/2, y_inc = 1;
// The bat position and how to increment to next position
private int playerX = 60;
private int playerY = PH/2, playerY_inc = 1;
double count = 0.00;
// Called on key press
class Transaction implements KeyListener // When character typed
{
public void keyPressed(KeyEvent e) // Obey this method
{
// Key typed includes specials
switch ( e.getKeyCode() ) // Character is
{
/*
case KeyEvent.VK_LEFT: // Left Arrow
x_inc = -1;
break;
case KeyEvent.VK_RIGHT: // Right arrow
x_inc = 1;
break;
*/
case KeyEvent.VK_UP: // Up arrow
playerY_inc = -1;
break;
case KeyEvent.VK_DOWN: // Down arrow
playerY_inc = 1;
break;
}
// x,y could send to a server instead of calling
repaint(); // Call update method
}
public void keyReleased(KeyEvent e)
{
switch ( e.getKeyCode() ) // Character is
{
/*
case KeyEvent.VK_UP: // Up arrow
playerY_inc = playerY_inc;
break;
case KeyEvent.VK_DOWN: // Down arrow
playerY_inc = playerY_inc;
break;
*/
}
}
public void keyTyped(KeyEvent e)
{
// Normal key typed
char c = e.getKeyChar(); // Typed
repaint(); // Redraw screen
}
}
private static final int B = 6; // Border offset
private static final int M = 26; // Menu offset
private static final int BALL_SIZE = 10; // Ball diameter
private static final int HALF_BALL_SIZE = BALL_SIZE/2;
//Players Bat
private static final int PW = 20;
private static final int PH = 100;
private static final int HALF_PLAYER = PH/2;
// Code called to draw the current state of the game
Rectangle2D.Double player;
Ellipse2D.Double ball;
public void drawActualPicture( Graphics2D g )
{
// White background
g.setPaint( Color.white );
g.fill( new Rectangle2D.Double( 0, 0, W, H ) );
Font font = new Font("Monospaced",Font.PLAIN,24);
g.setFont( font );
// Blue playing border
g.setPaint( Color.blue ); // Paint Colour
g.draw( new Rectangle2D.Double( B, M, W-B*2, H-M-B ) );
// Players Bat
g.setPaint( Color.green ); // Paint Colour
player = new Rectangle2D.Double( playerX, playerY, PW, PH );
g.fill(player);
// Display state of game
g.setPaint( Color.blue );
FontMetrics fm = getFontMetrics( font );
String fmt = "Score/ Time lasted = %3f";
String text = String.format( fmt, count );
g.drawString( text, W/2-fm.stringWidth(text)/2, M*2 );
// The ball at the current x, y position (width, height)
g.setPaint( Color.red );
ball = new Ellipse2D.Double( x-HALF_BALL_SIZE, y-HALF_BALL_SIZE, BALL_SIZE, BALL_SIZE );
g.fill( ball );
}
// Main program loop
public void run()
{
int ballS = 1; // Speed 1 - 5
int playerS = 1;
try
{
while ( true )
{
count = count + 0.015;
//Ball hitting walls
//Right wall
if ( x >= W-B-HALF_BALL_SIZE )
{
x_inc = -1*ballS;
}
//Left wall
if ( x <= 0+B+HALF_BALL_SIZE )
{
count = count;
break;
}
//Bottom Wall
if ( y >= H-B-HALF_BALL_SIZE )
{
y_inc = -1*ballS;
}
//Top Wall
if ( y <= 0+M+HALF_BALL_SIZE )
{
y_inc = 1*ballS;
}
//Player Hiting Wall
//Bottom Wall
if ( playerY >= H-B-100 )
{
playerY_inc = -1*playerS;
}
//Top Wall
if ( playerY <= 0+M )
{
playerY_inc = 1*playerS;
}
//Player
Rectangle2D ballB = ball.getBounds2D();
if ( ball.getBounds2D().intersects(player.getBounds2D() ))
{
System.out.println("true");
//x_inc = -1*ballS;
}
//Wall
x += x_inc;
y += y_inc;
playerY += playerY_inc;
repaint(); // Now display
Thread.sleep( 10 ); // 100 Hz
}
} catch ( Exception e ) {};
}
}
Edit: Solved it, I used math and x-y coords to work out if it was inside the other shape. Thanks the help.
Is a reference check as they are objects; not primitives. You are checking if the Rectangle2D returned by both the game objects are one in the same (which they aren’t).
To check if a Rectangle2D object intersects another Rectangle2D object you should do: