bouncing ball issue

[adam405]

I am trying to create a bouncing ball. At the momene the ball just travels off the applet screen instead of bouncing back. Any help is appreciated.

Code:

// import necessary packages
import java.applet.*;
import java.awt.*;
import java.util.Random;


public class FirstApplet extends Applet implements Runnable
{
    //position of the ball
    int x_pos = 1;
    int y_pos = 1;
    int first_x =1;
    int first_y =1;
   
    //ball size
    int radius = 5;
    
    //direction
    int x_speed = 1;
    int y_speed = 1;
    
    //applet size
    int appletsize_top = 10;
    int appletsize_bottom = 370;  
    int appletsize_left = 10;  
    int appletsize_right = 370;  
    //random movement
    Random rnd = new Random ();
    
    //Drawing image off screen
    private Image dbImage;
    private Graphics dbg;
    
    int maxspeed = 1;

// start - method is called every time you enter the HTML 
public void start ()
{
// define a new thread 
Thread th = new Thread (this);
// start this thread
th.start ();
}

	
	
//run- start the applet game
public void run () 
{ 
    while (true)
    {
    // lower ThreadPriority 
    Thread.currentThread().setPriority(Thread.MIN_PRIORITY);
    //change direction if ball hits right side
 
    if (x_pos > appletsize_left)
	{
            // Setzen der x - Position
		x_pos += first_x;
		y_pos += first_y;
                
		x_speed = (rnd.nextInt ()) % maxspeed;
        }

    else if (x_pos < appletsize_right)
	{
            // Setzen der x - Position
		x_pos += first_x;
		y_pos += first_y;
                
		x_speed = (rnd.nextInt ()) % maxspeed;
        }      
    
    else if (y_pos > appletsize_top)
	{
            // Setzen der x - Position
		x_pos += first_x;
		y_pos += first_y;
                
		x_speed = (rnd.nextInt ()) % maxspeed;
        } 
     else if (y_pos < appletsize_bottom)
	{
            // Setzen der x - Position
		x_pos += first_x;
		y_pos += first_y;
                
		x_speed = (rnd.nextInt ()) % maxspeed;
        } 
    
   
     //repaint applet
     repaint();

    try
    {
        // Stop thread for the speed
        Thread.sleep (10);
    }
    catch (InterruptedException ex)
    {
       
    }

        // set ThreadPriority to maximum value
        Thread.currentThread().setPriority(Thread.MAX_PRIORITY);
    
}
}

//create an image off screen and loads it into the applet
public void update (Graphics g)
{
// initialize buffer
if (dbImage == null)
{
dbImage = createImage (this.getSize().width, this.getSize().height);
dbg = dbImage.getGraphics ();
}

// clear screen in background
dbg.setColor (getBackground ());
dbg.fillRect (0, 0, this.getSize().width, this.getSize().height);

// draw elements in background
dbg.setColor (getForeground());
paint (dbg);

// draw image on the screen
g.drawImage (dbImage, 0, 0, this);
}




/** paint - method allows you to paint into your applet. This method is called e.g. if you move your browser window or if you call repaint() */
public void paint (Graphics g) 

{ 
    // set color
    g.setColor (Color.red);

    // paint a filled colored circle
    g.fillOval (x_pos - radius, y_pos - radius, 2 * radius, 2 * radius);


}

// Method to handle mouse down events 
public boolean mouseDown (Event e, int x, int y) 
{
    // Change direction, put speed into a minus number 1 now become -1
    x_speed = - (x_speed); 
    return true;
}


}

[hardwired]

Here's how you deal with deprecation warnings:

Code:

C:\jexp>javac firstappletrx.java
Note: firstappletrx.java uses or overrides a deprecated API.
Note: Recompile with -Xlint:deprecation for details.

C:\jexp>javac -Xlint:deprecation firstappletrx.java
firstappletrx.java:141: warning: [deprecation] mouseDown(java.awt.Event,int,int) in java.a
wt.Component has been deprecated
    public boolean mouseDown (Event e, int x, int y)
                   ^
1 warning

Code:

//  <applet code="FirstAppletRx" width="400" height="400"></applet>
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import java.util.Random;


public class FirstAppletRx extends Applet implements Runnable
{
    //position of the ball
    int x_pos = 12;
    int y_pos = 12;
//    int first_x = 1;
//    int first_y = 1;
   
    //ball size
    int radius = 5;
    
    //direction
    int x_speed = 3;
    int y_speed = 2;
    
    //applet size
    int appletsize_top = 10;
    int appletsize_bottom = 370;  
    int appletsize_left = 10;  
    int appletsize_right = 370;  
    //random movement
    Random rnd = new Random ();
    
    //Drawing image off screen
    private Image dbImage;
    private Graphics dbg;
    
    int maxspeed = 5;

    Thread thread;
    boolean running = false;

    public void init()
    {
        addMouseListener(ma);
    }

    // start - method is called after init
    // and every time the applet is maximized 
    public void start ()
    {
        // define a new thread 
        running = true;
        thread = new Thread (this);
        // start this thread
        thread.start ();
        System.out.println("start");
    }

    // A well–behaved Applet stops
    // its animation when minimized.
    public void stop()
    {
        running = false;
        if(thread != null)
            thread.interrupt();
        thread = null;
        System.out.println("stop");
    }

    //run- start the applet game
    // Implementation of the Runnable interface.
    public void run () 
    {
        while (running)
        {
            // lower ThreadPriority 
            Thread.currentThread().setPriority(Thread.MIN_PRIORITY);

            // change direction if ball hits any side
             if (x_pos < appletsize_left || x_pos > appletsize_right)
	    {
                x_speed *= -1;
            }

            if (y_pos < appletsize_top || y_pos > appletsize_bottom)
	    {
                y_speed *= -1;
            }

            x_pos += x_speed;
            y_pos += y_speed;

            //repaint applet
            repaint();

            try
            {
                // Stop thread for the speed
                Thread.sleep (50);
            }
            catch (InterruptedException ex)
            {
                running = false;
                break;
            }

            // set ThreadPriority to maximum value
            Thread.currentThread().setPriority(Thread.MAX_PRIORITY);
        }
    }

    //create an image off screen and loads it into the applet
    public void update (Graphics g)
    {
        // initialize buffer
        if (dbImage == null)
        {
            dbImage = createImage (this.getSize().width, this.getSize().height);
            dbg = dbImage.getGraphics ();
        }

        // clear screen in background
        dbg.setColor (getBackground ());
        dbg.fillRect (0, 0, this.getSize().width, this.getSize().height);

        // draw elements in background
        dbg.setColor (getForeground());
        paint (dbg);

        // draw image on the screen
        g.drawImage (dbImage, 0, 0, this);
    }

    /**
     *  paint - method allows you to paint into your applet.
     *  This method is called e.g. if you move your browser
     *  window or if you call repaint()
     */
    public void paint (Graphics g) 
    { 
        // set color
        g.setColor (Color.red);

        // paint a filled colored circle
        g.fillOval (x_pos - radius, y_pos - radius, 2 * radius, 2 * radius);
    }

    private MouseListener ma = new MouseAdapter()
    {
        // Method to handle mousePressed events        
        public void mousePressed(MouseEvent e) 
        {
            // Preserve the direction of x_speed [-:left +:right].
            //int sign = (int)Math.signum(x_speed);  // j2se 1.5+
            // or we can try:
            int sign = (x_speed > 0) ? 1 : -1;
            x_speed = 1 + rnd.nextInt(maxspeed);  // [1 - maxspeed]
            // Restore the sign.
            x_speed *= sign;
        }
    };
}