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Firing a projectile in mouse direction in java

I'm trying to fire a projectile in the mouse direction but i am having trouble.
The angles are wrong, and by that I mean it will only go up left or in the top-left corner.
This is my Gun class for which I fire the Bullet.
package assets;
import Reaper.Game;
import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
public class Gun
{
public ArrayList<Bullet> bullets;
protected double angle;
Mouse mouse = new Mouse();
private BufferedImage image;
private int centerX = Game.WIDTH / 2;
private int centerY = Game.HEIGHT;
public Gun()
{
bullets = new ArrayList<Bullet>();
image = null;
try
{
image = ImageIO.read(new File("assets/gun.png"));
}
catch (IOException e)
{
e.printStackTrace();
}
}
public BufferedImage loadImage()
{
return image;
}
public int getImageWidth()
{
return image.getWidth(null);
}
public int getImageHeight()
{
return image.getHeight(null);
}
public void rotate(Graphics g)
{
angle = Math.atan2(centerY - mouse.getMouseY(), centerX - mouse.getMouseX()) - Math.PI / 2;
((Graphics2D) g).rotate(angle, centerX, centerY);
g.drawImage(image, Game.WIDTH / 2 - image.getWidth() / 2,
900 - image.getHeight(), image.getWidth(), image.getHeight(),
null);
}
public Image getImage()
{
return image;
}
public void update()
{
shoot();
for (int i = 0; i < bullets.size(); i++)
{
Bullet b = bullets.get(i);
b.update();
}
}
public void shoot()
{
if (mouse.mouseB == 1)
{
double dx = mouse.getMouseX() - Game.WIDTH / 2;
double dy = mouse.getMouseY() - Game.HEIGHT / 2;
double dir = Math.atan2(dy, dx);
bullets.add(new Bullet(Game.WIDTH / 2, Game.HEIGHT / 2, dir));
mouse.mouseB = -1;
}
}
public void render(Graphics g)
{
for (int i = 0; i < bullets.size(); i++)
{
bullets.get(i).render(g);
}
rotate(g);
}
}
This is my Bullet class:
package assets;
import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
public class Bullet
{
private double dx, dy;
private int x, y;
private double dir;
private BufferedImage image;
public Bullet(int x, int y, double angle)
{
this.x = x;
this.y = y;
this.dir = angle;
image = null;
try
{
image = ImageIO.read(new File("assets/bolt.png"));
}
catch (IOException e)
{
e.printStackTrace();
}
dx = Math.cos(dir);
dy = Math.sin(dir);
}
public void update()
{
x += dx;
y += dy;
System.out.println("dx : " + dx + " " + dy);
}
public void render(Graphics g)
{
g.drawImage(image, x, y, image.getWidth(), image.getHeight(), null);
}
public BufferedImage getImage()
{
return image;
}
}
And this is the main Game class:
package Reaper;
import Reaper.graphics.Screen;
import assets.Gun;
import assets.Mouse;
import gameState.MenuState;
import javax.swing.*;
import java.awt.*;
import java.awt.image.BufferStrategy;
public class Game extends Canvas implements Runnable
{
private static final long serialVersionUID = 1L;
public static int WIDTH = 900;
public static int HEIGHT = 900;
public static int scale = 3;
public int frames = 0;
public int updates = 0;
private boolean running = false;
private Thread thread;
private JFrame frame;
#SuppressWarnings("unused")
private Screen screen;
private Gun gun;
private MenuState mns;
private Mouse mouse;
public Game()
{
Dimension size = new Dimension(WIDTH, HEIGHT);
setPreferredSize(size);
screen = new Screen(WIDTH, HEIGHT);
frame = new JFrame();
gun = new Gun();
mns = new MenuState();
mouse = new Mouse();
addMouseListener(mouse);
addMouseMotionListener(mouse);
}
public static void main(String[] args)
{
Game game = new Game();
game.frame.setResizable(false);
game.frame.add(game);
game.frame.pack();
game.frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
game.frame.setVisible(true);
game.frame.setLocationRelativeTo(null);
game.strat();
}
public void strat()
{
running = true;
thread = new Thread(this, "Reaper");
thread.start();
}
public void stop()
{
running = false;
try
{
thread.join();
}
catch (InterruptedException e)
{
e.printStackTrace();
}
}
public void run()
{
long timer = System.currentTimeMillis();
long lastTime = System.nanoTime();
double ns = 1000000000.0 / 60;
double delta = 0;
while (running)
{
long now = System.nanoTime();
delta += (now - lastTime) / ns;
lastTime = now;
while (delta >= 1)
{
update();
updates++;
delta--;
}
render();
frames++;
if (System.currentTimeMillis() - timer > 1000)
{
timer = System.currentTimeMillis();
frame.setTitle("Reaper! " + " | " + updates + " ups , " + frames + " fps");
updates = 0;
frames = 0;
}
}
stop();
}
public void update()
{
if (mns.play)
{
gun.update();
}
}
public void render()
{
BufferStrategy bs = getBufferStrategy();
if (bs == null)
{
createBufferStrategy(3);
return;
}
Graphics g = bs.getDrawGraphics();
g.fillRect(0, 0, WIDTH, HEIGHT);
if (mns.menu)
{
mns.draw(g);
}
if (mns.play)
{
g.clearRect(0, 0, WIDTH, HEIGHT);
g.drawImage(mns.getImage(), 0, 0, mns.getImageWidth(), mns.getImageHeight(), this);
gun.render(g);
}
if (mns.rules)
{
g.clearRect(0, 0, WIDTH, HEIGHT);
}
bs.show();
}
}
I know it's very badly coded, and I will try to fix it as much as I can, but I am really stuck on this. Searched around the web, tried some of the solutions but it wont work. I guess I'm doing it wrong by putting methods in wrong places and calling them, I guess.

I know it's very badly coded, and I will try to fix it as much as I can, ...
Next time, consider first cleaning up the mess and then asking the question.
(Are the variables storing the values returned by getMouseX() and getMouseY() really static?)
However, the main reason for the actual problem are the x and y values in the Bullet class:
class Bullet
{
private double dx, dy;
private int x, y;
....
public void update()
{
x += dx;
y += dy;
System.out.println("dx : " + dx + " " + dy);
}
...
}
They are declared as int values. Imagine what happens in the update method, for example, when x=0 and dx = 0.75: It will compute 0+0.75 = 0.75, truncate this to be an int value, and the result will be 0.
Thus, the x and y values will never change, unless the dx and dy values are >= 1.0, respectively.
Just changing the type of x and y to double will solve this. You'll have to add casts in the render method accordingly:
g.drawImage(image, (int)x, (int)y, ...);
But you should really clean this up.

mouse motion listener only in one direction

i have been working on mouse motion listener in Java couldn't sort it out completely because i want the object to move towards the direction where ever on the screen the mouse is pointed at but unforunately when the mouse is inside the applet window, the object moves only towards a single direction. Here is my code below..
import java.awt.*;
import java.awt.geom.*;
import java.util.*;
import java.applet.*;
import java.awt.event.*;
import javax.swing.*;
public class MouseOver extends Applet implements KeyListener, MouseListener,
MouseMotionListener {
private int[] Xpoints = { 0, -5, 5 };
private int[] Ypoints = { -10, -2, -2 };
private double xpos, ypos;
private Polygon poly;
int polyrot = 0;
private int width; // !! added
private int height; // !! added
public void init() {
poly = new Polygon(Xpoints, Ypoints, Xpoints.length);
addKeyListener(this);
addMouseListener(this);
addMouseMotionListener(this);
}
public void paint(Graphics g) {
Graphics2D g2d = (Graphics2D) g;
AffineTransform id = new AffineTransform();
width = getSize().width;
height = getSize().height;
g2d.setColor(Color.BLACK);
g2d.fillRect(0, 0, width, height);
g2d.setColor(Color.RED);
g2d.draw(poly);
g2d.translate(width / 2, height / 2);
g2d.rotate(Math.toRadians(polyrot));
g2d.scale(5, 5);
}
public void keyReleased(KeyEvent k) {
}
public void keyTyped(KeyEvent k) {
}
public void keyPressed(KeyEvent k) {
switch (k.getKeyCode()) {
case KeyEvent.VK_LEFT:
if (polyrot < 0) {
polyrot = 359;
polyrot++;
}
repaint();
break;
case KeyEvent.VK_RIGHT:
if (polyrot > 360) {
polyrot = 0;
polyrot--;
}
repaint();
break;
}
}
public void mouseEntered(MouseEvent m) {
}
public void mouseExited(MouseEvent m) {
}
public void mouseReleased(MouseEvent m) {
}
public void mouseClicked(MouseEvent m) {
}
public void mousePressed(MouseEvent m) {
switch (m.getButton()) {
case MouseEvent.BUTTON1:
if (polyrot < 0) {
polyrot = 359;
polyrot--;
}
repaint();
break;
case MouseEvent.BUTTON2:
if (polyrot > 360) {
polyrot = 0;
polyrot++;
}
repaint();
break;
}
}
public void mouseMoved(MouseEvent e) {
xpos = getX();
if (xpos < 0) {
polyrot--;
} else if (xpos > 0) {
polyrot++;
}
repaint();
// !! break; // Doesn't belong here
}
#Override
public void mouseDragged(MouseEvent e) {
// You forgot this method
}
}

Your problem is with this line:
public void mouseMoved(MouseEvent e){
xpos=getX(); // ******
if(xpos<0){polyrot--;}
else if(xpos>0){polyrot++;}
repaint();
break;
}
That returns the x position of the applet not the mouse cursor. You need to use your MouseEvent object, e and instead get the mouse's position. Change it to:
xpos = e.getX();
Please don't ignore the comment that I made to your question. Please remember that we're volunteers who help on our free time. Please don't make it any more difficult than it has to be to help you.
I've tried to edit your code so that it compiles, and now is indented. Consider creating a Swing application, not an AWT application, since Swing apps are more flexible, powerful and robust.

This:
if (xpos < 0) {
means "if the cursor is outside of the panel".
This:
xpos = getX();
does not get a mouse coordinate.
Change your event to something like this:
public void mouseMoved(MouseEvent e) {
xpos = e.getX();
if (xpos < getWidth() / 2) {
polyrot--;
} else {
polyrot++;
}
repaint();
}
Now it rotates counter-clockwise if the cursor is on the left side of the panel and clockwise if the cursor is on the right side.
This:
g2d.draw(poly);
g2d.translate(width / 2, height / 2);
g2d.rotate(Math.toRadians(polyrot));
g2d.scale(5, 5);
will not do anything to change the image because you are doing your transforming after drawing it.
This:
Graphics2D g2d = (Graphics2D) g;
is a bad idea because you are applying transforms to the global graphics context which would carry on to subsequent repaints of other components.
Change your paint to something like this:
public void paint(Graphics g) {
super.paint(g);
Graphics2D g2d = (Graphics2D) g.create();
width = getSize().width;
height = getSize().height;
g2d.setColor(Color.BLACK);
g2d.fillRect(0, 0, width, height);
g2d.translate(width / 2, height / 2);
g2d.rotate(Math.toRadians(polyrot));
g2d.scale(5, 5);
g2d.setColor(Color.RED);
g2d.draw(poly);
g2d.dispose();
}
Further reading:
Painting in AWT and Swing
How to Write a Mouse Listener

There are a few things...
In your keyPressed and mousePressed events, are are only ever process the out of bounds conditions, for example...
if (polyrot < 0) {
polyrot = 359;
polyrot++;
}
//...
if (polyrot > 360) {
polyrot = 0;
polyrot--;
}
But you never process what it should do when it's within the acceptable bounds (0-359)...
Instead, you could simply add or subtract the amount from polyrot and allow the API to deal with it (surprisingly, it's capable for dealing with angles < 0 and > 359), for example...
public void mousePressed(MouseEvent m) {
switch (m.getButton()) {
case MouseEvent.BUTTON1:
polyrot--;
repaint();
break;
case MouseEvent.BUTTON2:
polyrot++;
repaint();
break;
}
}
Now, I'm not sure what you mean by "object to move towards the direction where ever on the screen the mouse is pointed". Does this mean that the object should actually change it's x/y coordinates or should it just "look" at the mouse cursor...
Based on the fact that you actually have no movement code and you basically have the object painted in a fixed location, I'm assuming "look at"...
Basically, you need to know where the mouse is and where the object is, then determine the angle between them...
public void mouseMoved(MouseEvent e) {
int x = width / 2;
int y = height / 2;
Point mousePoint = e.getPoint();
int deltaX = mousePoint.x - x;
int deltaY = mousePoint.y - y;
polyrot = -Math.atan2(deltaX, deltaY);
polyrot = Math.toDegrees(polyrot) + 180;
repaint();
}
You should note that I changed 'polyrot' to 'double'
Your paint method is also wrong. Basically, you are painting your object BEFORE you've transformed it, instead, you should be using something more like...
g2d.translate(width / 2, height / 2);
g2d.rotate(Math.toRadians(polyrot));
g2d.draw(poly);
You should also be calling super.paint(g) before you apply you own custom painting...
As a side note, you should avoid overriding paint of top level containers, like JApplet, but instead, create a custom component, extending from something like JPanel and override it's paintComponent method, performing your custom painting there (don't forget to call super.paintComponent). Take a look at Performing Custom Painting for more details
You should also avoid using KeyListener and instead use the Key Bindings API as it doesn't suffer from the same focus issues that KeyListener does...
Updated with runnable example
So I had a play around with code and produced this simple example...
Basically, I tossed out Polygon in favour of Path2D, basically because it provides much greater functionality and is easy to deal with when scaling ;)
import java.applet.Applet;
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.Polygon;
import java.awt.Rectangle;
import java.awt.Shape;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.geom.AffineTransform;
import java.awt.geom.Path2D;
public class MouseOver extends Applet implements KeyListener, MouseListener,
MouseMotionListener {
private double xpos, ypos;
private Path2D poly;
private double polyrot = 0;
private int width; // !! added
private int height; // !! added
public void init() {
poly = new Path2D.Double();
poly.moveTo(0, 10);
poly.lineTo(5, 0);
poly.lineTo(10, 10);
poly.lineTo(0, 10);
poly.closePath();
addKeyListener(this);
addMouseListener(this);
addMouseMotionListener(this);
}
public void paint(Graphics g) {
super.paint(g);;
Graphics2D g2d = (Graphics2D) g;
AffineTransform id = new AffineTransform();
width = getSize().width;
height = getSize().height;
g2d.setColor(Color.BLACK);
g2d.fillRect(0, 0, width, height);
g2d.setColor(Color.RED);
id.scale(5, 5);
Shape scaled = poly.createTransformedShape(id);
Rectangle bounds = scaled.getBounds();
g2d.translate((width - bounds.width) / 2, (height - bounds.height) / 2);
g2d.rotate(Math.toRadians(polyrot), bounds.width / 2, bounds.height / 2);
g2d.setStroke(new BasicStroke(5f, BasicStroke.CAP_ROUND, BasicStroke.JOIN_ROUND));
g2d.draw(scaled);
}
public void keyReleased(KeyEvent k) {
}
public void keyTyped(KeyEvent k) {
}
public void keyPressed(KeyEvent k) {
switch (k.getKeyCode()) {
case KeyEvent.VK_LEFT:
polyrot++;
repaint();
break;
case KeyEvent.VK_RIGHT:
polyrot--;
repaint();
break;
}
}
public void mouseEntered(MouseEvent m) {
}
public void mouseExited(MouseEvent m) {
}
public void mouseReleased(MouseEvent m) {
}
public void mouseClicked(MouseEvent m) {
}
public void mousePressed(MouseEvent m) {
switch (m.getButton()) {
case MouseEvent.BUTTON1:
polyrot--;
repaint();
break;
case MouseEvent.BUTTON2:
polyrot++;
repaint();
break;
}
}
public void mouseMoved(MouseEvent e) {
int x = width / 2;
int y = height / 2;
Point mousePoint = e.getPoint();
int deltaX = mousePoint.x - x;
int deltaY = mousePoint.y - y;
polyrot = -Math.atan2(deltaX, deltaY);
polyrot = Math.toDegrees(polyrot) + 180;
repaint();
}
#Override
public void mouseDragged(MouseEvent e) {
// You forgot this method
}
}

From here:
public void mouseMoved(MouseEvent e){
xpos=getX();
if(xpos<0){polyrot--;}
else if(xpos>0){polyrot++;}
repaint();
break;
}
It seems you update only the xpos. You should update also the variable ypos.
You might want to do it with something like this:
ypos=e.getY();
if (this.ypos<0){
this.polyrot--;
}else if (this.ypos>0) {
this.polyrot++;
}
this.repaint();

Loop in a JApplet animation Java

import java.awt.Graphics;
import javax.swing.JApplet;
import javax.swing.JPanel;
public class Circle extends JPanel {
int x = 75;
int y = 100;
int diameter = 50;
public void setAnimationY(int y) {
this.y = y;
}
public int getAnimationY() {
return y;
}
public int getDiameter() {
return diameter;
}
public void setDiameter(int startDiameter) {
diameter = startDiameter;
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawOval(x, y, diameter, diameter);
}
}
import java.awt.BorderLayout;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JApplet;
import javax.swing.JPanel;
import javax.swing.Timer;
public class BouncingBall extends JApplet {
private int speed = 5;
private Timer timer;
private Circle draw;
#Override
public void init() {
super.init();
setLayout(new BorderLayout());
draw = new Circle();
add(draw);
timer = new Timer(30, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
int y = draw.getAnimationY();
int diameter = draw.getDiameter();
int roof = getHeight();
y += speed;
if (y < 0) {
y = 0;
speed *= -1;
} else if (y + diameter > roof) {
y = roof - diameter;
speed *= -1;
}
draw.setAnimationY(y);
repaint();
}
});
}
#Override
public void start() {
super.start();
timer.start();
}
#Override
public void stop() {
timer.stop();
super.stop();
}
}
I am trying to create a JApplet that contains a ball that is bouncing up and down. So far I have been able to get the ball to go up and down but now I am trying to make the ball more "life-like" so I want the height of the ball to decrease each time the ball bounces until eventually it stops.
I have attempted to do a while loop using the roof variable that I created for the getHeight() method but for some reason when I tried to use it either the ball didn't move at all or the loop had no affect on the ball.
I have also tried a for loop but I ran into the same problem that I got into with the while loop. I believe the problem is that I am not placing this for loop in the correct spot for it to work correctly.
thanks in advance.

Little modifications to your code that can give you some trails:
#Override
public void actionPerformed(ActionEvent e) {
int y = draw.getAnimationY();
int diameter = draw.getDiameter();
int roof = getHeight();
y += speed;
//
// Reduce the ball size at the bottom of the screen
//
if(y + diameter > roof) {
if(diameter > minDiameter) {
diameter -= (roof - y);
} else {
diameter = minDiameter;
}
} else if (diameter < maxDiameter) {
diameter++;
}
draw.setDiameter(diameter);
if (y < 0) {
y = 0;
speed *= -1;
} else if (y + diameter > roof) {
y = roof - diameter;
speed *= -1;
}
// Simulates a little gravity
speed += 0.5;
draw.setAnimationY(y);
repaint();
}
For more realism, the best way would to find an equation that is function of the ball position and a coefficient of hardness for the ball and would give you the ball size.

Well let use continue with #MadProgrammer's solution from your other related question:
In your class of DrawPane we can easily define the height, getAnimationHeight() and setAnimationHeight(int) to control the height decrease as soon as it touches the ground. Please remember that in java left-top co-ordinate is (0, 0) and right-bottom co-ordinate is (getWidth(), getHeight()). Suppose that it starts from height = 0(top). Then it will start from y = height(top) and eventually move to the getHeight()(bottom) of your container. We will increase the height(top y) using setAnimationHeight() by adding an amount(say 30) to current height(which getAnimationHeight() will return) .
So, this little tweak made to #MadeProgrammer's solution in your other question will be the following demo.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.Timer;
public class Circle extends JApplet {
private int delta = 8;
private Timer timer;
private DrawPane drawPane;
#Override
public void init() {
super.init();
setLayout(new BorderLayout());
drawPane = new DrawPane();
add(drawPane);
timer = new Timer(100, new ActionListener() {
int frameCount = 0;
#Override
public void actionPerformed(ActionEvent e) {
int y = drawPane.getAnimationY();
int diameter = drawPane.getDiameter();
y += delta;
if (y < drawPane.getAnimationHeight()) {
y = drawPane.getAnimationHeight();
delta *= -1;
} else if (y + diameter > getHeight()) {
y = getHeight()- diameter;
delta *= -1;
int animationHeight = drawPane.getAnimationHeight();
animationHeight = animationHeight + (getHeight() - diameter - animationHeight)/2;
drawPane.setAnimationHeight(animationHeight);
if(animationHeight + diameter + 2 >= getHeight())
{
System.out.println("true");
drawPane.setAnimationY(getHeight() - diameter);
repaint();
timer.stop();
return;
}
}
drawPane.setAnimationY(y);
repaint();
}
});
}
#Override
public void start() {
super.start();
timer.start();
}
#Override
public void stop() {
timer.stop();
super.stop();
}
public class DrawPane extends JPanel {
int x = 100;
int y = 0;
int diameter = 50;
int height = 0;
public void setAnimationX(int x) {
this.x = x;
}
public void setAnimationY(int y) {
this.y = y;
}
public void setAnimationHeight(int h)
{
height = h;
}
public int getAnimationHeight()
{
return height;
}
public int getAnimationX() {
return x;
}
public int getAnimationY() {
return y;
}
public int getDiameter() {
return diameter;
}
public void setDiameter(int startDiameter) {
diameter = startDiameter;
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawOval(x, y, diameter, diameter);
}
}
}
NOTE: As soon as it touches the bottom finally, you should stop the Timer to get rid of the flickering of the ball. This task is left as an exercise for you.

Filling polygon and moving it, but its leaving a trail

Alright, so I've been trying to move my polygon so it bounces around the screen. Right now it does so but leave a trail the entire way. I have a GUI class, extended by an Aquarium class, which fills the screen with the color blue, creates a "creature" object (from Creature class) and uses update to move it down the screen. When it updates however, a trail is left behind. I have tried many methods mentioned in similar cases on the site but nothing works. Can somebody please help me?
GUI class (that holds JPanel etc)
package artilife;
import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class AquariumGUI {
private GooPanel gooPanel;
private boolean loop = true;
protected int width, height;
private int frameTimeInMillis = 300;
private RenderingHints renderingHints = new RenderingHints(
RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
#SuppressWarnings("serial")
class GooPanel extends JPanel {
public void paintComponent(Graphics g) {
Graphics2D g2d = (Graphics2D) g;
g2d.setRenderingHints(renderingHints);
draw(g2d);
}
}
public AquariumGUI() {
this(800, 500);
}
public AquariumGUI(int w, int h) {
width = w;
height = h;
JFrame frame = new JFrame();
frame.setSize(width, height);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
gooPanel = new GooPanel();
gooPanel.setPreferredSize(new Dimension(w, h));
frame.getContentPane().add(gooPanel);
frame.pack();
frame.setVisible(true);
}
public void go() {
while (loop) {
gooPanel.repaint();
update();
try {
Thread.sleep(frameTimeInMillis);
} catch (InterruptedException e) {
}
}
}
public void draw(Graphics2D g) {
}
public void update(){
}
public void setFrameTime(int millis){
frameTimeInMillis = millis;
}
}
Aquarium class that extended this and attempts to color the screen and place a Polygon creature on it:
package artilife;
import java.awt.Color;
import java.awt.Graphics2D;
import java.util.ArrayList;
import java.util.Random;
public class MyAquarium extends AquariumGUI {
Creature tester;
public MyAquarium()
{
tester = new Creature();
}
public void draw(Graphics2D g) {
// Fill background
g.setColor(Color.WHITE);
g.fillRect(0, 0, width, height);
tester.draw(g);
}
public void update(){
tester.move(width, height);
}
public static void main(String[] args) {
MyAquarium aquarium = new MyAquarium();
aquarium.go();
}
}
And the creature that is being drawn, and holds the move method:
package artilife;
import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Creature
{
// Position and radius of the drop
private double x, y, r, Vx, Vy;
Polygon p = new Polygon();
int numSides;
public Creature() {
x = 800 / 2;
r = 10;
y = 50;
Vx = 10;
Vy = 3;
numSides = 3;
//creatureShape(numSides);
}
public void creatureShape (int sides)
{
if (sides <= 10){
for (int i = 0; i < sides; i++){
p.addPoint((int) (x + 50 * Math.cos((i) * 2 * Math.PI / sides)),
(int) (y + 50 * Math.sin((i) * 2 * Math.PI / sides)));
}
}
else{
for (int i = 0; i < 360; i++) {
double value = i / 360.0;
p.addPoint((int) (90 + 50 * value * Math.cos(8 * value * Math.PI)),
(int) (50 + 50 * value * Math.sin(8 * value * Math.PI)));
}
}
}
public void draw(Graphics2D g) {
creatureShape(numSides);
g.setColor(Color.BLUE);
g.fillPolygon(p);
}
public void move(int width, int height){
// Move the drop
x = x + Vx;
y = y +Vy;
if (y >= height){
Vy = -Vy;
y = height;
}
else if(y <= 0){
Vy = -Vy;
y = 0;
}
if(x >= width){
Vx = -Vx;
x = width;
}
if(x <= 0){
Vx = -Vx;
x = 0;
}
}
/*
public void attraction ()
{
if (
}*/
/*
public boolean check4Creatures ()
{
boolean isThere = false;
//if there is an another create object within a 60 point radius
isThere = true;
return isThere;
}*/
}

SOLUTION:
So fiddle for what feels like forever and it works now.
When drawing polygons in motion, some java functions store bits of information regarding the vertices. The best way to move them cleanly is to use translate() instead of manipulating the vertices directly (by updating x and y values) when updating the information, and then draw the fresh polygon.
Thank everyone for taking the time to look at my problem though!

You need to clear the screen between two drawing operations. You can either leave it to the framework, by calling the super.paintComponent() method, or you can do it your way, by filling the screen with something, like a g.fillRect() call.
The first method will actually make a call the the fillRect function, using the panel background color.

Using a JLabel to continuously update a score in Java, JFrame-based game

I'm building a little "pong" game in Java.
I'm trying to add a scorekeeper up top that shows the updated score (+1) everytime the player saves the ball with the paddle.
I'm trying to use a JLabel but the problem is that I can't think of a way to continuously update the JLabel each time the paddle is hit.
Any ideas?
My code:
MainPanel Class (the one with the Paddle and Ball and Label)
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
//import swing.graphics.BounceFrame;
//import swing.graphics.Circle;
public class MainPanel extends JPanel implements ActionListener, KeyListener, Runnable{
public Paddle paddle;
public Ball ball;
public MainPanel(){
ball = new Ball(50, 50, 10); //centerX, centerY, radius
setSize(300, 300);
paddle = new Paddle();
JLabel scoreKeeper = new JLabel("Score" + ball.getScore());
add(scoreKeeper);
Thread thread = new Thread(this);
thread.start();
}
public void paint(Graphics g) {
super.paint(g);
Graphics2D g2 = (Graphics2D)g;
paddle.draw(g2);
ball.draw(g2);
}
public void actionPerformed(ActionEvent e) {
String direction = e.getActionCommand();
switch(direction){
case "left": Paddle.movePaddleLeft(); break;
case "right": Paddle.movePaddleRight(); break;
}
this.repaint();
}
public void run() {
try {
while(true){
ball.move(getBounds());
repaint();
Thread.sleep(500/30);
}
}
catch (Exception e) {
e.printStackTrace();
}
}
#Override
public void keyPressed(KeyEvent e) {
if (e.getKeyCode() == 37){
Paddle.movePaddleLeft();
}
if (e.getKeyCode() == 39){
Paddle.movePaddleRight();
}
}
#Override
public void keyReleased(KeyEvent e) {
}
#Override
public void keyTyped(KeyEvent e) {
}
}
And my Ball class:
import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Rectangle2D;
import java.util.Random;
public class Ball {
private Ellipse2D ball;
private double radius;
private double ballCircumference;
private Color color;
private double x;
private double y;
private double dx = 5;
private double dy = 5;
private int score = 0;
public int getScore() {
return score;
}
//Boundaries to determine if ball is hit by paddle
private double criticalBoundaryX;
private double criticalBoundaryY1;
private double criticalBoundaryY2;
private double paddleHalfwayPoint;
private boolean inGame = true;
public void recalculateCriticals(){
criticalBoundaryX = Paddle.getYPosition() - ballCircumference;
criticalBoundaryY1 = Paddle.getXPosition()- ballCircumference; //Left boundary
criticalBoundaryY2 = Paddle.getXPosition()+Paddle.getPaddleWidth()+ballCircumference; //Right Boundary
paddleHalfwayPoint = (Paddle.getXPosition()+Paddle.getPaddleWidth())/2;
}
public Ball(int centerX, int centerY, int radius) {
this.x = centerX - radius;
this.y = centerY - radius;
this.radius = radius;
ballCircumference = 2*radius;
Random randomRGB = new Random();
color = new Color(randomRGB.nextInt(255), randomRGB.nextInt(255), randomRGB.nextInt(255));
this.ball = new Ellipse2D.Double(x, y, 2*radius, 2*radius);
}
public void move(Rectangle2D bounds) {
recalculateCriticals();
x += dx;
y += dy;
if (x < bounds.getMinX()) {
x = bounds.getMinX();
dx = -dx;
}
if (x + 2*radius >= bounds.getMaxX()) {
//System.out.println(bounds.getMaxX());
x = bounds.getMaxX() - 2*radius;
dx = -dx;
}
if (y < bounds.getMinY()) {
y = bounds.getMinY();
dy = -dy;
}
if (y > criticalBoundaryX){
if (x < criticalBoundaryY1 || x > criticalBoundaryY2){
inGame = false;
}
if (!inGame && hittingEdge(x))
dx = -dx;
}
if (y > criticalBoundaryX && inGame){ //When it hits the paddle
changeColor();
score++;
y = criticalBoundaryX;
dy = -dy;
}
if (y > bounds.getMaxY()){
System.out.println("Game Over");
System.exit(0);
}
recalculateCriticals();
ball.setFrame(x, y, 2*radius, 2*radius);
}
public boolean onPaddle(double x){
return ((x > Paddle.getXPosition()) && (x < Paddle.getXPosition()+Paddle.getPaddleWidth()) && (y > Paddle.getYPosition()-10));
}
public boolean hittingEdge(double x){
return ((x >= criticalBoundaryY1 && x < paddleHalfwayPoint)
||
(x <= criticalBoundaryY1 && x > paddleHalfwayPoint)); //Return true if x is hitting the side edge of the paddle
}
public void changeColor(){
Random randomColor = new Random();
color = new Color(randomColor.nextInt(255), randomColor.nextInt(255), randomColor.nextInt(255));
}
public void draw(Graphics2D g2) {
g2.setColor(color);
g2.fill(ball);
}
}

The "Java way" of doing this would be to define a listener interface, for example:
public interface BallListener {
void paddleHit();
}
In the Ball class, you should add a field
private List<BallListener> listeners;
as well as methods
public void addBallListener(BallListener l) { listeners.add(l); }
public void removeBallListener(BallListener l) { listeners.remove(l); }
When the paddle is hit, you go:
for (BallListener l : listeners)
l.paddleHit();
The main class should implement the BallListener interface, and register itself with the ball (ball.addBallListener(this)).
This approach also enables you to, when needed, inform other parts of your program about different events that happen to the ball (i.e. add a new method to BallListener for each event you'd like to signal).