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I'm trying to make this Bouncing Ball program have the ball bounce around in the window, but no matter what I do, it bounces once and then just goes indefinitely out of the screen. What do I do to make it stay in the screen?
/*
* File: BouncingBall.java
* This program graphically simulates a bouncing ball.
*
*
*/
import java.awt.event.*;
import java.awt.Graphics;
import java.awt.Color;
import javax.swing.JPanel;
import javax.swing.JFrame;
import javax.swing.Timer;
public class BouncingBall
{
public static void main()
{
JFrame frame = new JFrame( "Bouncing Ball" );
frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
BallPanel bp = new BallPanel();
frame.add( bp );
frame.setSize( 600, 300 ); // set frame size
frame.setVisible( true ); // display frame
} // end main
}
// class BallPanel
class BallPanel extends JPanel implements ActionListener
{
private int delay = 15;
protected Timer timer;
private int x = 0; // x position
private int y = 0; // y position
private int diameter = 20; // ball diameter
private int velX = 2; // velocity offset for x
private int velY = 2; // velocity offset for y
public BallPanel()
{
timer = new Timer(delay, this);
timer.start(); // start the timer
}
public void actionPerformed(ActionEvent e) // This method runs when timer done
{
repaint(); // repaint panel to make ball in different place
}
public void paintComponent( Graphics g ) // determine ball position
{
super.paintComponent( g ); // call superclass's paintComponent
g.setColor(Color.black); // set ball to black
if (y > getHeight()) // make ball bounce off floor
{
velY = -velY;
}
x += velX; // add velocity offset for new position
y += velY; // add velocity offset for new position
g.fillOval(x, y, diameter, diameter);
}
}
You only detect that the ball has hit the floor. You need to also check if the ball has hit the ceiling;
if (y < 0) // make ball bounce off ceiling
{
velY = 2;
}
Similarly you will need to check for it hitting the left and right sides...
You only check the Y-Coordinate and only that if is below 0.
if(y <= 0 || y >= 300 || x <= 0 || x >= 600)
Replace that with your if-statement and it should work.
Related
I am currently working on a 3 cushion billiards game project. I have added two balls on the table so far. I am trying to move one of the balls but I am having a hard time doing that. Should I use a timer? If so then could you tell me an effective way to use the timer on my code so I can move my balls?
Your help would be much appreciated.
Thanks in advance.
Farhan Hasan
I have tried to create a move function for the class balls. But I am not sure what I should put inside the function, I have added the xSpeed and ySpeed. The xLocation and the yLocation changes depending on the xSpeed and ySpeed.
public class Balls
{
private Color ballFillColor;
private Color ballBorderColor;
private int ballX = 0;
private int ballY = 0;
private int xSpeed = 5;
private int ySpeed = 0;
private int ballWidth = 0;
private int ballHeight = 0;
Timer t;
public boolean fillBall = false;
private static Balls ballArray[]; //Required for drawMultipleBalls
Balls(){ //Constructor
ballBorderColor = Color.black;
}
Balls(int ballX, int ballY, int ballWidth, int ballHeight, Color ballBorderColor, JFrame window){ //Constructor
// X , Y , Width, Height, Border Colour, container
this.setBallBorderColor(ballBorderColor);
this.setBallWidth(ballWidth);
this.setBallHeight(ballHeight);
this.setBallX(ballX);
this.setBallY(ballY);
this.drawBall(window);
}
//Here is the move function. I am not really sure what to do here.
public void move()
{
if(this.ballX < 1000 - this.ballWidth)
{
this.ballX += this.xSpeed;
}
try
{
Thread.sleep(1);
}
catch(Exception e)
{
}
}
//GET AND SET FUNCTIONS HERE
//HERE ARE THE FUNCTIONS WHICH ARE RESPONSIBLE FOR DRAWING MY BALLS IN JFRAME
public void drawBall(JFrame frame)
{
frame.getContentPane().add(new MyComponent());
}
public void drawMultipleBalls(JFrame frame, Balls[] balls)
{
ballArray = balls;
frame.getContentPane().add(new MyComponent2());
}
private class MyComponent extends JComponent{
public void paintComponent(Graphics g){
if (fillBall) //Fill first, and then draw outline.
{
g.setColor(ballFillColor);
g.fillOval(getBallX(),getBallY(), getBallHeight(),getBallWidth());
}
g.setColor(getBallBorderColor());
g.drawOval(getBallX(),getBallY(), getBallHeight(),getBallWidth());
}
}
private class MyComponent2 extends JComponent{
public void paintComponent(Graphics g){
for (int i = 0; i < ballArray.length; i++)
{
if (ballArray[i].fillBall) //Fill first, and then draw outline.
{
g.setColor(ballArray[i].ballFillColor);
g.fillOval(ballArray[i].getBallX(),ballArray[i].getBallY(), ballArray[i].getBallHeight(),ballArray[i].getBallWidth());
}
g.setColor(ballArray[i].getBallBorderColor());
g.drawOval(ballArray[i].getBallX(),ballArray[i].getBallY(), ballArray[i].getBallHeight(),ballArray[i].getBallWidth());
}
}
}
Hopefully, I can have two movable balls for the game, the should bounce back as the hit the edge of the screen and they should be able to slow down over time. For that, I am thinking to use a damper (I will multiply the xSpeed and ySpeed with a number less than 1, eventually it will slow down the ball)
Here is a simple example I came up with to show a ball moving and bouncing off the edges.
The direction changes based on the boundary. Left and top edges just check for 0. Bottom and right edges need to include the diameter of the ball.
The x and y increments are independent. And these amounts in conjunction with the timer can change the movement. Notice however, that to have objects bounce off of each other (as in a pool game) is more complicated due to angle of trajectories, etc. And the distances bounced will vary and slow with time based on frictional values. Everything else is documented in the Java API.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class MovementDemo extends JPanel implements ActionListener {
JFrame frame = new JFrame("Movement Demo");
int size = 500;
int x = 50;
int y = 200;
int diameter = 50;
int yinc = 2;
int xinc = 2;
int xdirection = 1;
int ydirection = 1;
public MovementDemo() {
setPreferredSize(new Dimension(size, size));
frame.add(this);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> new MovementDemo().start());
}
public void start() {
Timer timer = new Timer(100, this);
timer.setDelay(5);
timer.start();
}
public void actionPerformed(ActionEvent ae) {
if (x < 0) {
xdirection = 1;
}
else if (x > size - diameter) {
xdirection = -1;
}
if (y < 0) {
ydirection = 1;
}
else if (y > size - diameter) {
ydirection = -1;
}
x = x + xdirection * xinc;
y = y + ydirection * yinc;
repaint();
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
g2d.setColor(Color.BLUE);
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
g2d.fillOval(x, y, diameter, diameter);
}
}
It seems in general there are a few things you need to figure out:
has the ball collided with another ball
has the ball collided with a wall
otherwise just figure out what is the ball's new position based on its velocity
Below is some sample code that stubs some of this out. You can first compare the current ball's position to all others (not including the current ball of course). If there are any equal positions, process a collision with a ball. If the ball is at the window border i.e it hit a wall, process a collision with a wall. Otherwise just calculate its new position based on its current velocity.
The process collision part is just to apply physics mechanics to whatever degree of complexity you require. One general suggested change would be to update the velocity of the balls then apply it to the position after. The specific calculations for velocity changes you could apply as needed and as you can imagine it can get pretty involved which is why I suggest using a separate method and possibly a sub class for velocity instead of managing each part of the velocity vector in the ball itself. I used the wall as an object because of this. The composition, weights, velocities etc of the object's colliding can affect the resulting collision, but how complex you want that processing to be is up to you.
Sorry I'm no physics expert but I hope this sends you in the right direction in terms of code! Also this might help with the specific calculations you might want to use:
https://www.khanacademy.org/science/physics/one-dimensional-motion/displacement-velocity-time/v/calculating-average-velocity-or-speed
public void move()
{
// check if balls are on same position not including this ball
for(Ball b: ballArray){
if (this.position == b.position && this != b){
processCollision(this, b, null);
} else{
// if the ball hasn't collided with anything process its movement based on speed
// this assumes a 1000 x 1000 window for keeping objects inside it
if(this.ballX < 1000 - this.ballWidth && this.ballY < 1000 - this.ballHeight){
this.ballX += this.xSpeed;
this.ballY += this.ySpeed;
}else {
processCollision(this, null, new Wall());
}
}
}
try
{
Thread.sleep(1);
}
catch(Exception e)
{
}
}
public void processCollision(Ball b1, Ball b2, Wall w){
// if ball hasn't collided with a wall, process a ball - ball collision
if(w == null){
// apply physics mechanics according the complexity desired for ball collisions
b1.xSpeed -= b2.xSpeed;
b1.ySpeed -= b2.ySpeed;
// ball 2 would end up slowing down
b2.xSpeed -= b1.xSpeed;
b2.ySpeed -= b1.ySpeed;
}
// if ball hasn't collided with a ball, process a ball - wall collision
if(b2 == null){
// apply physics mechanics for hitting a wall
// e.g as below: just send ball in opposite direction
b1.xSpeed = b1.xSpeed * -1;
b1.ySpeed = b1.ySpeed * -1;
}
// either way, process ball's new position based on its new speed
b1.ballX += b1.xSpeed;
b1.ballY += b1.ySpeed;
b2.ballX += b2.xSpeed;
b2.ballY += b2.ySpeed;
}
For the purposes of my project, I'm trying to simulate a phyllotaxis pattern by creating multiple circles in real time using the formulas given.
So recently, I've decided to try out GUI programming in Java using JFrame and swing, and I've hit a wall trying to figure out how to get everything running properly. My idea was to slowly print out circle after circle with their x and y coordinates being calculated from the "r = cos/sin(theta)" formulas documented in the phyllotaxis instructions. Unfortunately, while the x and y values are constantly changing, only one circle is printed. Is there something I am missing?
package gExample;
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Random;
import javax.swing.JFrame;
import javax.swing.Timer;
public class GraphicsExample extends Canvas implements ActionListener {
private final static int HEIGHT = 600;
private final static int WIDTH = 600;
private int n = 0;
private int x, y;
Timer t = new Timer(20, this);
public static void main(String args[]) {
JFrame frame = new JFrame();
GraphicsExample canvas = new GraphicsExample();
canvas.setSize(WIDTH, HEIGHT);
frame.add(canvas);
frame.pack();
frame.setVisible(true);
frame.setResizable(false);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
canvas.setBackground(Color.black);
}
public void paint(Graphics g){
Random rand = new Random();
Color col = new Color(rand.nextInt(256), rand.nextInt(256), rand.nextInt(256));
g.setColor(col);
/*each time paint() is called, I expect a new circle to be printed in the
x and y position that was updated by actionPerformed(), but only one inital circle is created. */
g.fillOval(x, y, 8, 8);
t.start();
}
#Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
int c = 9;
double r = c * Math.sqrt(n);
double angle = n * 137.5;
//here, every time the method is called, the x and y values are updated,
//which will be used to fill in a new circle
int x = (int) (r * Math.cos(angle * (Math.PI / 180) )) + (WIDTH / 2);
int y = (int) (r * Math.sin(angle * (Math.PI / 180) )) + (HEIGHT / 2);
//when the program is running, this line of code is executed multiple times.
System.out.println("x: " + x + " y: " + y);
n++;
}
}
Ok so I have been try to get this ball to bounce naturally for a few weeks now and can't seem to get it right. The program should allow the user to input a set amount of gravity and then have the ball bounce according to that amount. It works for the first few bounces but stopping the ball is the problem. I have to deliberately set its movement to 0 or else it will endlessly bounce in place but not move on the x-axis. This issue only happens when the gravity is set to 15, other amount and things really go bad. The ball will bounce naturally but then keep rolling on x-axis forever. I've never taken a physics class so the issue is probably in the physics code. Anyone know where the issue is?
Here is the code my code-
import java.applet.Applet;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;
import java.util.Random;
import javax.swing.JOptionPane;
//key stuff
import java.awt.KeyEventDispatcher;
import java.awt.KeyboardFocusManager;
import java.awt.event.KeyEvent;
public class StartingPoint extends Applet implements Runnable{
//key press
private static boolean wPressed = false;
public static boolean isWPressed() {
synchronized (StartingPoint.class) {
return wPressed;
}
}
//for position of circle
int x = 0;
int y= 0;
//for position change
double dx = 2;
double dy = 2;
//for circle size
int rad = 11;
//image for update()
private Image i;
private Graphics gTwo;
//Physics
double grav = 15;
double engloss= .65;
double tc = .2;
double friction = .9;
#Override
public void init() {
// sets window size
setSize(800,600);
}
#Override
public void start() {
//"this" refers to the implemented run method
Thread threadOne = new Thread(this);
//this goes to run()
threadOne.start();
}
#Override
public void run() {
String input = JOptionPane.showInputDialog( "How much gravity?" );
grav= Double.parseDouble(input);
// sets frame rate
while (true){
//makes sure it doesn't go off screen x wise
//right side
if (x + dx > this.getWidth() - rad -1){
x= this.getWidth() -rad -1; //blocks it from moving past boundary
dx = -dx; //Reveres it
}
//left side
else if (x + dx < 1 + rad){
x= 1+rad; //ball bounces from the center so it adjusts for this by adding one and rad to pad out the radius of the ball plus one pixel.
dx = -dx; //Inverters its movement so it will bounce
}
//makes the ball move
else{
x += dx; // if its not hitting anything it keeps adding dx to x so it will move.
}
//friction
if(y == this.getHeight()-rad -1){
dx *= friction; //every time the ball hits the bottom dx is decreased by 10% by multiplying by .9
//Keeps it from micro bouncing for ever
if (Math.abs(dy) < 4){ // if the speed of y (dy) is less than .4 it is set to 0
dy= 0;
}
/**if (Math.abs(dx) < .00000000000000000001){ // if the speed of x (dx) is less than .00000000000000000001 it is set to 0, this value doesn't seem to matter
dx = 0;
}**/
}
//makes sure it doesn't go off screen y wise
//down
if (y > this.getHeight() - rad -0){ // TODO Check how getHieght is measured.
y= this.getHeight() -rad -0;
//makes ball loose speed.
dy *= engloss;
dy = -dy;
}
else {
//velocity
// tc makes grav smaller. Total of which is added to dy. To increase velocity as the ball goes down.
dy += grav *tc;
//gravity
//new dy is decreased by tc + .5 multiplied by gravity and tc squared. This makes the ball bounce lower every time based on its speed
y += dy*tc + .5*grav*tc*tc;
}
//frame rate
repaint();
try {
Thread.sleep(17);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
//end frame rate
}
#Override
public void stop() {
}
#Override
public void destroy() {
}
#Override
public void update(Graphics g) {
//keeps it from flickering... don't know how though
if(i == null){
i = createImage(this.getSize().width, this.getSize().height);
gTwo = i.getGraphics();
}
gTwo.setColor(getBackground());
gTwo.fillRect(0, 0, this.getSize().width, this.getSize().height);
gTwo.setColor(getForeground());
paint(gTwo);
g.drawImage(i, 0, 0, this);
//do some thing with setDoubleBuffered
}
#Override
public void paint(Graphics g) {
g.setColor(Color.BLUE);
g.fillOval(x-rad, y-rad, rad*2, rad*2);
}
}
Exercise1609: Write a program that draws line segments using the arrow keys. The line starts from the center of the frame and draws towards east,north, west, or south when the right-arrow key, up-arrow key, left-arrow key, or down-arrow key is pressed. In short, draw a maze. See comments below for a description of my question.
import java.awt.*;
import java.awt.event.*;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class Exercise1609 extends JFrame {
private KeyboardPanel panel = new KeyboardPanel();
public Exercise1609() {
add(panel);
panel.setFocusable(true);
}
public static void main(String[] args) {
Exercise1609 frame = new Exercise1609();
frame.setTitle("Tegn med piltaster");
frame.setSize(600, 300);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
//The panel that listens for key and responds by drawing
public static class KeyboardPanel extends JPanel {
private int x,y,previousX,previousY;
private boolean firstTime = true;
public KeyboardPanel() {
/**
* why must x and y be initialized inside paintComponent?
* if I want to start drawing from the middle of the panel?
* If I remove the if-block inside paintComponent and instead
* place the initialization here, as shown with the two lines below:
* x = previousX = getWidth() / 2;
* y = previousY = getHeight() / 2;
* ...then the program will not start to draw from the middle,
* but upper left corner of the screen
*/
addKeyListener(new KeyAdapter() {
#Override
public void keyPressed(KeyEvent e) {
previousY = y;
previousX = x;
switch (e.getKeyCode()) {
case KeyEvent.VK_DOWN:
y++;
break;
case KeyEvent.VK_UP:
y--;
break;
case KeyEvent.VK_RIGHT:
x++;
break;
case KeyEvent.VK_LEFT:
x--;
break;
}
repaint();
}
});
}//end constructor
#Override
protected void paintComponent(Graphics g) {
super.paintComponents(g);
if(firstTime) {
//Why can't x and y be initialized outiside paintComponent?
//Why can't they be initialized inside the constructor of this class?
x = previousX = getWidth() / 2;
y = previousY = getHeight() / 2;
firstTime = false;
}
g.drawLine(previousX, previousY, x, y);
System.out.println(x + " " + y);
}
}
}
The last line System.out.println(x + " " + y); outputs 0,0 if I try to initialize x and y anywhere else
but paintComponent(). When initialized inside paintcomponent() the output is 292,131...which is what I want.
getWidth() and getHeight() are not set correctly until the UI elements have gone through a layout pass. This is guaranteed to happen before paintComponent() is called but probably not at other points where you have tried to call them.
See: getWidth() and getHeight() are 0 after calling setPreferredSize()
If you need to be notified when the width and height of the component is set/changed, check out ComponentListener: http://docs.oracle.com/javase/7/docs/api/java/awt/event/ComponentListener.html
I'm writing a program taken from the TV show, THE OFFICE, when they're sitting in the conference room and watching the bouncing DVD logo on the screen try to hit the corner. The square is supposed to change color when it hits an edge.
However, I'm running into a few issues.
Issue one: The Square sometimes bounces off an edge. Other times it sinks, and I can't figure out why.
Issue two: I'm not sure how to change the color of the square when it hits the edge.
Issue three: I'm trying to learn how to make a JFRAME fullscreen. And not just fullscreen on my screen but on anyone's.
THE CODE HAS BEEN POSTED TO AN ONLINE IDE FOR EASIER READING. That can be found HERE
Otherwise if you're too busy for that link. Here it is posted below.
import java.util.Random;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class BouncingMischievousSquare extends JPanel implements ActionListener {
private static final int SQUARE_SIZE = 40;
private static final int SPEED_OF_SQUARE = 6;
private int xPosit, yPosit;
private int xSpeed, ySpeed;
BouncingMischievousSquare(){
//speed direction
xSpeed = SPEED_OF_SQUARE;
ySpeed = -SPEED_OF_SQUARE;
//a timer for repaint
//http://docs.oracle.com/javase/tutorial/uiswing/misc/timer.html
Timer timer = new Timer(100, this);
timer.start();
}
public void actionPerformed(ActionEvent e){
//Screensize
int width = getWidth();
int height = getHeight();
xPosit += xSpeed;
yPosit += ySpeed;
//test xAxis
if(xPosit < 0){
xPosit = 0;
xSpeed = SPEED_OF_SQUARE;
}
else if(xPosit > width - SQUARE_SIZE){
xPosit = width - SQUARE_SIZE;
xSpeed = -SPEED_OF_SQUARE;
}
if(yPosit < 0){
yPosit = 0;
ySpeed = SPEED_OF_SQUARE;
}
else if(yPosit > height - SQUARE_SIZE){
xPosit = height - SQUARE_SIZE;
xSpeed = -SPEED_OF_SQUARE;
}
//ask the computer gods to redraw the square
repaint();
}
public void paintComponent(Graphics g){
super.paintComponent(g);
g.fillRect(xPosit, yPosit, SQUARE_SIZE, SQUARE_SIZE );
}
}
MAIN CLASS
import javax.swing.*;
public class MischievousMain {
public static void main(String[] args) {
JFrame frame = new JFrame("Bouncing Cube");
frame.setSize(500, 500);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// mischievous square input
frame.add(new BouncingMischievousSquare());
frame.setVisible(true);
}
}
Anyways, Thanks for taking the time to read through my code. It's appreciated. I'm really interested in different ways to go about this.
Issue one: The Square sometimes bounces off an edge. Other times it
sinks, and I can't figure out why.
You'll hate yourself for this, but
} else if (yPosit > height - SQUARE_SIZE) {
xPosit = height - SQUARE_SIZE;
xSpeed = -SPEED_OF_SQUARE;
}
Should be...
} else if (yPosit > height - SQUARE_SIZE) {
yPosit = height - SQUARE_SIZE;
ySpeed = -SPEED_OF_SQUARE;
}
You were using xPosyit and xSpeed instead of yPosyit and ySpeed...
Issue two: I'm not sure how to change the color of the square when it
hits the edge.
Basically, whenever you detect a edge collision and change direction, simple change the panel's foreground color to something else...
This might require you to have a list of colors from which you can randomly pick or simply randomly generate the color
Then in your paintComponent method, simple use g.setColor(getForeground()) before you fill the rect...
...ps...
To make life easier, you could just write a method that either generates a random color or sets the foreground to a random color, for example...
protected void randomiseColor() {
int red = (int) (Math.round(Math.random() * 255));
int green = (int) (Math.round(Math.random() * 255));
int blue = (int) (Math.round(Math.random() * 255));
setForeground(new Color(red, green, blue));
}
Issue three: I'm trying to learn how to make a JFRAME fullscreen. And
not just fullscreen on my screen but on anyone's.
Take a look at Full-Screen Exclusive Mode API