noob needs paint help

[ed jones]

hi,

this is some code taken from the net, modified a bit, that I'm trying to understand. The idea is to bounce a ball. Currently the ball bounces in a continuous line, but I can't see where I'm messing up.

  package MyBreakout;
 
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.Rectangle;
import java.awt.image.BufferedImage;
import java.util.ArrayList;
 
import javax.swing.JApplet;
 
public class MyBreakout extends JApplet implements Runnable{
 
/**
 * 
 */
private static final long serialVersionUID = 1L;

 

Rectangle    paddle;
Ball        ball;
ArrayList   blocks;
Thread       thread;


public Image offScreenImage;
public Graphics bufferGraphics;
 


int paddleX;
int paddleY;
int ballX;
int ballY;
int appwidth;
int appheight;
int numblocks;
int numrows;
int speed;

//===============================================================================init
public void init()
{

    Dimension appletSize = this.getSize();  
    int appheight = appletSize.height;
    int appwidth = appletSize.width;
    
    
    offScreenImage = createImage(appwidth,appheight);
bufferGraphics = offScreenImage.getGraphics();
         

ball = new Ball(50,100,15,5,appwidth, appheight);
paddle = new Rectangle( 50, appheight-30, 50, 10 );
blocks = new ArrayList( );

 thread = new Thread(this);
        thread.start( );
 

numblocks = 10;
numrows = 5;
speed = 10;
 

}//init

//==================================================================================run
public void run()
{

Thread.currentThread().setPriority(Thread.MIN_PRIORITY);

while(true)
{    
ball.move();
repaint();


 try {
                Thread.sleep(15);
            }catch( Exception ex ) { }
            
            Thread.currentThread().setPriority(Thread.MAX_PRIORITY);
 

}//while

}


//===================================================================================update
 public void update( Graphics g )
    {
        paint(g);
    }
 
 
//====================================================================================paint
public void paint(Graphics g)
{
    bufferGraphics.setColor(Color.WHITE);
 
    bufferGraphics.fillRect(0,0,appwidth,appheight);
        ball.paint( bufferGraphics );
      
    g.drawImage(offScreenImage,0,0,this);
    
}


}//class MyBreakout
 
package MyBreakout;
 
import java.awt.Color;
import java.awt.Graphics;
 
class Ball
{
    int x, y,w,h, size, speed;
    int dirX, dirY;
    int appwidth, appheight;
    public Ball( int _x, int _y, int _size,  int _speed, int w, int h )
    {
        x = _x;
        y = _y;
        size = _size;
        speed = _speed;
        dirX = 1;
        dirY = 1;
        appwidth = w;
        appheight = h;
    }
  
public void paint( Graphics g )
    {
        g.setColor( Color.BLUE );
        g.fillOval( x, y, size, size );
    }
    public void move( )
    {
        x = x + speed * dirX;
        y = y + speed * dirY;
        if ( x < 0 )
            dirX = 1;
        else if ( x > appwidth )
            dirX = -1;
        if ( y < 0 )
            dirY = 1;
        else if ( y > appheight )
            dirY = -1;
    }
}
 

  

thanks for your time

[Campbell Ritchie]

Some very old-fashioned looking code there, with _x and _y. That is an acceptable format in C, but not considered correct style in Java.
And some odd features like an empty catch and a SUID of 1L. Also using thread priorities (which is probably unnecessary) may lose portability.

Try super.paint(g); as the first line of the paint() method.