[5151] in java-interest
Bouncing Ball program...
daemon@ATHENA.MIT.EDU (Paul Benati)
Tue Jan 30 10:11:58 1996
Date: Tue, 30 Jan 1996 08:32:15 -0500
To: java-interest@java.sun.com
From: Paul Benati <benatip@pcd.kodak.com>
Anyone out there have any suggestions as to how to make this bouncing
ball bounce smoothly?
Paul
--------------------------[ code below ]-----------------------------
import java.awt.*;
import java.lang.*;
// ------------------------------------------------------------------------
// ------------------------------------------------------------------------
public class Bounce extends Frame
{
private static final int TimeInterval = 75;
private static Ball ball = new Ball();
private Panel mainPanel = new Panel();
private long time = 0;
private boolean doQuit = false;
private boolean moveBall = true;
private Dimension frameSize;
// ----------------------------------------------------------------------
// ----------------------------------------------------------------------
public
Bounce(String title)
{
setTitle(title);
setBackground(Color.red);
add("Center", ball);
}
// ----------------------------------------------------------------------
// ----------------------------------------------------------------------
public
void go()
{
time = System.currentTimeMillis();
while(doQuit != true)
{
if((moveBall) && ((time + TimeInterval) <= System.currentTimeMillis()))
{
frameSize = size();
ball.moveBall(frameSize.width, frameSize.height);
time = System.currentTimeMillis();
}
}
}
// ----------------------------------------------------------------------
// ----------------------------------------------------------------------
public
boolean handleEvent(Event e)
{
boolean handled = false;
switch (e.id)
{
case e.MOUSE_DOWN:
{
if(moveBall)
moveBall = false;
else
moveBall = true;
break;
}
case e.MOUSE_UP:
{
break;
}
case e.KEY_PRESS:
{
System.exit(0);
break;
}
case e.WINDOW_DESTROY:
{
System.exit(0);
break;
}
} // end of switch statement
return handled;
}
// ----------------------------------------------------------------------
// ----------------------------------------------------------------------
public
static void main(String args[])
{
Bounce bounce = new Bounce("Bounce");
bounce.pack();
bounce.show();
bounce.go();
}
// ----------------------------------------------------------------------
// ----------------------------------------------------------------------
public
Dimension preferredSize()
{
return(new Dimension(200, 300));
}
}
// ------------------------------------------------------------------------
// ------------------------------------------------------------------------
class Ball extends Panel
{
private static double Gravity = 1.0; // pid/cron^2
private static double TimeUnit = 1.0; // cron
private int radius;
private int diameter;
private int xOrigin;
private int yOrigin;
private int xVelocity;
private int yVelocity;
public
Ball()
{
xOrigin = 50;
yOrigin = 50;
radius = 20;
diameter = radius*2;
xVelocity = 5;
yVelocity = 0;
setBackground(Color.white);
resize(200, 300);
}
// --------------------------------------------------------------------
// --------------------------------------------------------------------
public
void calculateBallPosition(int windowWidth, int windowHeight)
{
xOrigin += (int) (xVelocity + 0.5*Gravity*TimeUnit*TimeUnit);
yOrigin += (int) (yVelocity + 0.5*Gravity*TimeUnit*TimeUnit);
// ------------------------------------------------------------------
// Reflect ball from wall if necessary!
// ------------------------------------------------------------------
if((xOrigin + radius) >= windowWidth)
{
xOrigin = windowWidth - ((xOrigin + radius) - windowWidth + radius);
xVelocity = -(Math.abs(xVelocity) - 1);
}
else if((xOrigin - radius) <= 0)
{
xOrigin = -((xOrigin - radius) - radius);
xVelocity = (Math.abs(xVelocity) - 1);
}
// ------------------------------------------------------------------
// Reflect ball from wall if necessary!
// ------------------------------------------------------------------
if((yOrigin + radius) >= windowHeight)
{
yOrigin = windowHeight - ((yOrigin + radius) - windowHeight + radius);
yVelocity = -(Math.abs(yVelocity) - 1);
}
else if((yOrigin - radius) <= 0)
{
yOrigin = -((yOrigin - radius) - radius);
yVelocity = (Math.abs(yVelocity) - 1);
}
}
// --------------------------------------------------------------------
// --------------------------------------------------------------------
public
void calculateBallVelocity()
{
yVelocity = yVelocity + (int) (Gravity*TimeUnit);
}
// --------------------------------------------------------------------
// --------------------------------------------------------------------
public
void calculateBallVelocity(int xPosition1, int yPosition1,
int xPosition2, int yPosition2)
{
xVelocity = (xPosition2 - xPosition1)/10;
yVelocity = (yPosition2 - yPosition1)/10;
}
// --------------------------------------------------------------------
// --------------------------------------------------------------------
public
void moveBall(int windowWidth, int windowHeight)
{
repaint(1, xOrigin - radius, yOrigin - radius, diameter, diameter);
calculateBallVelocity();
calculateBallPosition(windowWidth, windowHeight);
repaint(1, xOrigin - radius, yOrigin - radius, diameter, diameter);
}
// --------------------------------------------------------------------
// --------------------------------------------------------------------
public
void paint(Graphics g)
{
g.setXORMode(getBackground());
g.drawOval(xOrigin - radius, yOrigin - radius, diameter, diameter);
g.fillOval(xOrigin, yOrigin, 2, 2);
}
// --------------------------------------------------------------------
// --------------------------------------------------------------------
public
Dimension preferredSize()
{
return(new Dimension(200, 300));
}
}
Paul Benati
Digital Imaging Evangelist
Software Engineer/Imaging Scientist
Eastman Kodak Company benatip@kodak.com
http://www.kodak.com/ ftp.kodak.com
901 Elmgrove Road (716) 253 - 1775 (EP Office)
Rochester, NY 14653-5555 (716) 726 - 7295 (EP Fax)
233 - 1775 (KMX/Internal)
"I know that you believe you understand what you think I said, but
I am not sure you realize that what you heard is not what I meant."
-- by unknown author.
-
This message was sent to the java-interest mailing list
Info: send 'help' to java-interest-request@java.sun.com
