Stuttering Swing Animation

Stuttering Swing Animation - java

I'm attempting to recreate Pong, and can't quite get the animations to run as smooth as I would like them too. Sometimes the ball does motion where it slows and then jerks really fast. Where in my code do I go wrong? Also, if you could review my code as well it's be appreciated. I'm just trying to get better.
Code for the ball
import java.awt.geom.Ellipse2D;
public class Ball extends Ellipse2D.Double{
//Ball movement variables
boolean movementX = true;
boolean movementY = true;
// Player one info
private int p1Number = 0;
private String p1Score = "0";
// Player two info
private int p2Number = 0;
private String p2Score = "0";
// Constructor
public Ball(double x, double y){
this.x = x;
this.y = y;
height = 20;
width = 20;
}
//function created to move the puck based on the position of the Puck, and the Players
public void MovePuck(double PlayerX, double PlayerY, double PlayerTwoX, double PlayerTwoY) {
// automatically move the X values
if (movementX) {
x+=5;
if (x >= 580) {
movementX = false;
}
} else {
x-=5;
if (x <= 0) {
movementX = true;
}
}
// automatically move the Y values
if (movementY) {
y+=2;
if (y >= 380) {
movementY = false;
}
} else {
y-=2;
if (y <= 0) {
movementY = true;
}
}
// Make Puck Bounce Off Player One
if(x == PlayerX + 10 && y <= PlayerY + 50 && y >= PlayerY){
movementX = true;
}
// Make Puck Bounce off Player Two
if(x == PlayerTwoX - 10 && y <= PlayerTwoY + 50 && y >= PlayerTwoY){
movementX = false;
}
}
// function created to keep track of Player One's Score
public String p1Score(){
if(x == 580){
p1Number++;
}
p1Score = String.valueOf(p1Number);
return p1Score;
}
// function created to keep track of Player Two's Score
public String p2Score(){
if (x == 0) {
p2Number++;
}
p2Score = String.valueOf(p2Number);
return p2Score;
}
}
Code for the ball
import java.awt.geom.Rectangle2D;
public class Rectangle extends Rectangle2D.Double{
private boolean isMovingUp, isMovingDown;
public Rectangle(double x, double y){
this.x = x;
this.y = y;
width = 10;
height = 50;
}
public void movePlayerUP(){
y-=3;
}
public void movePlayerDown(){
y+=3;
}
public void setMovingDown(boolean movingDown) {
isMovingDown = movingDown;
}
public boolean isMovingDown() {
return isMovingDown;
}
public void setMovingUp(boolean movingUp) {
isMovingUp = movingUp;
}
public boolean isMovingUp() {
return isMovingUp;
}
#Override
public double getY() {return super.getY();}
public double getX(){return super.getX();}
}
And finally, the Board that holds the logic. The main just calls this and runs it.
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.image.BufferedImage;
public class Board extends JPanel {
private BufferedImage background;
//player one information
private int p1X = 20;
private int p1Y = 150;
private Rectangle playerOne;
//player two information
private int p2X = 550;
private int p2Y = 150;
private Rectangle playerTwo;
// puck information
private int PuckX = 290;
private int PuckY = 190;
private Ball Puck;
public Board() {
// creating each player and puck
playerOne = new Rectangle(p1X, p1Y);
playerTwo = new Rectangle(p2X, p2Y);
Puck = new Ball(PuckX, PuckY);
setDoubleBuffered(true);
addKeyBinding(this, KeyEvent.VK_UP, "moveUpPressed", false, (evt) -> {
playerOne.setMovingUp(true);
});
addKeyBinding(this, KeyEvent.VK_UP, "moveUpReleased", true, (evt) -> {
playerOne.setMovingUp(false);
});
addKeyBinding(this, KeyEvent.VK_DOWN, "moveDownPressed", false, (evt) -> {
playerOne.setMovingDown(true);
});
addKeyBinding(this, KeyEvent.VK_DOWN, "moveDownReleased", true, (evt) -> {
playerOne.setMovingDown(false);
});
addKeyBinding(this, KeyEvent.VK_W, " moveP2UpPressed", false, (evt) -> {
playerTwo.setMovingUp(true);
});
addKeyBinding(this, KeyEvent.VK_W, " moveP2UpReleased", true, (evt) -> {
playerTwo.setMovingUp(false);
});
addKeyBinding(this, KeyEvent.VK_S, " moveP2DownPressed", false, (evt) -> {
playerTwo.setMovingDown(true);
});
addKeyBinding(this, KeyEvent.VK_S, " moveP2DownReleased", true, (evt) -> {
playerTwo.setMovingDown(false);
});
// Timer to represent frames per second and constantly check the status of each button pressed
Timer timer = new Timer(20, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
// Move puck
Puck.MovePuck(playerOne.getX(), playerOne.getY(), playerTwo.getX(), playerTwo.getY());
repaint();
//Only move if the player is pressing each button
//Player One Moving UP
if(playerOne.isMovingUp()){
playerOne.movePlayerUP();
}
//Player One Moving Down
if(playerOne.isMovingDown()){
playerOne.movePlayerDown();
}
//Player Two Moving Up
if(playerTwo.isMovingUp()){
playerTwo.movePlayerUP();
}
//Player Two Moving Down
if(playerTwo.isMovingDown()){
playerTwo.movePlayerDown();
}
}
});
//Start Timer
timer.start();
}
// Created a function that represents adding keybinding. Easier than re-writing a function each time
public void addKeyBinding(JComponent comp, int keyCode, String id, boolean movement, ActionListener ActionListener){
InputMap im = comp.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW);
ActionMap ap = comp.getActionMap();
im.put(KeyStroke.getKeyStroke(keyCode, 0 , movement), id);
ap.put(id, new AbstractAction() {
#Override
public void actionPerformed(ActionEvent e) {
ActionListener.actionPerformed(e);
repaint();
}
});
}
public void paintComponent(Graphics g) {
super.paintComponents(g);
setOpaque(false);
// setting background with image
background = new BufferedImage(600, 400, BufferedImage.TYPE_INT_RGB);
g.drawImage(background, 0, 0, this);
// drawing player one
g.setColor(Color.blue);
((Graphics2D) g).fill(playerOne);
// drawing player two
g.setColor(Color.red);
((Graphics2D) g).fill(playerTwo);
// drawing puck
g.setColor(Color.orange);
((Graphics2D) g).fill(Puck);
//Player One Score
g.setColor(Color.white);
g.setFont(new Font("Arial", Font.PLAIN, 20));
g.drawString(Puck.p1Score(), 100, 30);
//Player Two Score
g.setColor(Color.white);
g.setFont(new Font("Arial", Font.PLAIN, 20));
g.drawString(Puck.p2Score(), 450, 30);
g.dispose();
}
}

Related

Moving two objects in the same class on a JFrame in Java

I have a project I am working on in that I have to create two objects, I would like the big rectangle(BLUE) to move around the frame every time I press the arrow keys on my keyboard while the small rectangle(RED) is moving away, once the big square touches/tags the small rectangle, screen refreshes and I can move the big rectangle again to chase down the small rectangle. Below is my main class, and IT class where I have implemented my two shapes.
The goal is to have the two rectangles, small rectangle runs away in the frame every time the big rectangle comes close until it's tagged. Would also have to add some kind of score panel on the frame to show updated scores and a timer to count down when the player starts playing.
I need help having the two rectangles move differently and not on top of each other. I would like the second rectangle to move away every time the first rectangle comes close to it moving around the Frame
`
My class IT
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
public class IT extends JPanel implements ActionListener, KeyListener {
Timer shapeTimer = new Timer(5, this);
public double xPos = 0, yPos = 0, movementX = 0, movementY = 0;
public int rectSize = 50;
public int rectSize2 = 35;
public int windowWidth;
int windowHeight;
public int xBound;
public int yBound;
public IT(int w, int h){
shapeTimer.start();
addKeyListener(this);
setFocusable(true);
setFocusTraversalKeysEnabled(false);
windowWidth = w;
windowHeight = h;
xBound = (windowWidth - rectSize);
yBound = (windowHeight - rectSize);
}
public void paintComponent(Graphics g){
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
Rectangle2D movableRect = new Rectangle2D.Double(xPos, yPos, rectSize, rectSize);
g2.setColor(Color.BLUE);
g2.draw(movableRect);
g2.fill(movableRect);
Rectangle2D movableRect2 = new Rectangle2D.Double(xPos, yPos, rectSize2, rectSize2);
g2.setColor(Color.RED);
g2.draw(movableRect2);
g2.fill(movableRect2);
}
public void actionPerformed(ActionEvent e){
repaint();
xPos += movementX;
yPos += movementY;
}
public void moveUp(){
if (yPos == 0){
movementY = 0;
movementX = 0;
}
movementY = -0.5;
movementX = 0;
}
public void moveDown(){
if (yPos == yBound){
movementY = 0;
movementX = 0;
}
movementY = 0.5;
movementX = 0;
}
public void moveLeft()
{
if (xPos == 0){
movementY = 0;
movementX = 0;
}
movementX = -0.5;
movementY = 0;
}
public void moveRight(){
if (xPos == xBound)
{
movementY = 0;
movementX = 0;
}
movementX = 0.5;
movementY = 0;
}
public void enlargeSquare(){
rectSize++;
rectSize2++;
}
public void shrinkSquare(){
rectSize--;
rectSize2--;
}
public void keyPressed(KeyEvent e){
int keyCode = e.getKeyCode();
if (keyCode == KeyEvent.VK_UP){
moveUp();
}
if (keyCode == KeyEvent.VK_DOWN){
moveDown();
}
if (keyCode == KeyEvent.VK_RIGHT){
moveRight();
}
if (keyCode == KeyEvent.VK_LEFT){
moveLeft();
}
if (keyCode == KeyEvent.VK_OPEN_BRACKET)
{
shrinkSquare();
}
if (keyCode == KeyEvent.VK_CLOSE_BRACKET)
{
enlargeSquare();
}
}
public void keyTyped(KeyEvent e){
}
public void keyReleased(KeyEvent e){
int keyCode = e.getKeyCode();
if (keyCode == KeyEvent.VK_UP){
movementX = 0;
movementY = 0;
}
if (keyCode == KeyEvent.VK_DOWN){
movementX = 0;
movementY = 0;
}
if (keyCode == KeyEvent.VK_RIGHT){
movementX = 0;
movementY = 0;
}
if (keyCode == KeyEvent.VK_UP){
movementX = 0;
movementY = 0;
}
}
}
`
MainTester class
`
import javax.swing.*;
import javax.swing.JFrame;
public class MainTester {
public static void main(String[] args) {
// TODO Auto-generated method stub
int frameWidth = 850;
int frameHeight = 650;
JFrame frmMain = new JFrame();
frmMain.setSize(frameWidth, frameHeight);
IT it = new IT(frameWidth, frameHeight);
frmMain.add(it);
frmMain.setVisible(true);
frmMain.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frmMain.setTitle("Tag Game");
}
}
`

Use key bindings, seriously, this is going to solve a swagger of issues related to KeyListener.
Decouple and seperate your logic. Each "entity" should be a self contained unit of work. In your case, they should contain information about their color, location and size at a minimum.
For simplicity, I started out with something which could just be painted...
public interface Entity {
public void paint(Graphics2D g2d);
}
Now, you could have a lot of different interfaces which reflect this which can be painted, moved, controlled, represents effects or what ever you need - then your classes should implement the interfaces they need. Then, your engine just deals with the "concepts" it wants to - need all "paintable" entities, need all "movable" entities, etc, when it needs to.
Next I created a concept of a "player". A player is a "paintable" entity, but which can be controlled by the player in some way, so it takes the current state of the "input"s and updates itself based on those states (more about that to come)
public static class PlayerEntity implements Entity {
protected static final int DELTA = 2;
private Rectangle bounds = new Rectangle(0, 0, 35, 35);
private Color fillColor;
public PlayerEntity(Color fillColor, Point location) {
this.fillColor = fillColor;
this.bounds.setLocation(location);
}
public Color getFillColor() {
return fillColor;
}
public Rectangle getBounds() {
return bounds;
}
public Point getCenter() {
return new Point((int)getBounds().getCenterX(), (int)getBounds().getCenterY());
}
public void update(Set<PlayerAction> actions, Dimension size) {
Rectangle currentBounds = getBounds();
int x = currentBounds.x;
int y = currentBounds.y;
if (actions.contains(PlayerAction.UP)) {
y -= DELTA;
}
if (actions.contains(PlayerAction.DOWN)) {
y += DELTA;
}
if (actions.contains(PlayerAction.LEFT)) {
x -= DELTA;
}
if (actions.contains(PlayerAction.RIGHT)) {
x += DELTA;
}
if (y < 0) {
y = 0;
}
if (y + currentBounds.height > size.height) {
y = size.height - currentBounds.height;
}
if (x < 0) {
x = 0;
}
if (x + currentBounds.width > size.width) {
x = size.width - currentBounds.width;
}
getBounds().setLocation(x, y);
}
#Override
public void paint(Graphics2D g2d) {
g2d.setColor(getFillColor());
g2d.fill(getBounds());
}
}
For reference, PlayerAction represents all the valid actions which can be performed by the player, for simplicity sake, I've just stuck to movement:
public enum PlayerAction {
UP, DOWN, LEFT, RIGHT;
}
Next I created a "monster" entity, in this case, the "monster" will always try and follow the player, this implementation is loosely based on Java: Move image towards mouse position
public static class MonsterEntity implements Entity {
protected static final int DELTA = 1;
private Rectangle bounds = new Rectangle(0, 0, 15, 15);
private Color fillColor;
public MonsterEntity(Color fillColor, Point location) {
this.fillColor = fillColor;
this.bounds.setLocation(location);
}
public Color getFillColor() {
return fillColor;
}
public Rectangle getBounds() {
return bounds;
}
public Point getCenter() {
return new Point((int)getBounds().getCenterX(), (int)getBounds().getCenterY());
}
public void moveTowards(Point target) {
Rectangle bounds = getBounds();
Point center = getCenter();
int xDelta = target.x < center.x ? -DELTA : DELTA;
int yDelta = target.y < center.y ? -DELTA : DELTA;
getBounds().setLocation(bounds.x + xDelta, bounds.y + yDelta);
}
#Override
public void paint(Graphics2D g2d) {
g2d.setColor(getFillColor());
g2d.fill(getBounds());
}
}
The monster is always trying to move it's center to the target location (which will eventually be the center of the player)
Now, this is where things become complicated.
We need:
A renderable surface onto which we can paint the player and monster(s)
Input bindings
A "game loop" to update the state of the entities and schedule repaints
For simplicity, I started with a JPanel, made use of Swing Timer and the key bindings API.
public class MainPane extends JPanel {
// This represents the "input bindings", these represent
// abstract actions which can be applied to the player
// or game state.
private enum InputKey {
PRESSED_UP, PRESSED_DOWN, PRESSED_LEFT, PRESSED_RIGHT,
RELEASED_UP, RELEASED_DOWN, RELEASED_LEFT, RELEASED_RIGHT;
public KeyStroke getKeyStroke() {
switch (this) {
case PRESSED_UP: return KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0, false);
case PRESSED_DOWN: return KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0, false);
case PRESSED_LEFT: return KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0, false);
case PRESSED_RIGHT: return KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0, false);
case RELEASED_UP: return KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0, true);
case RELEASED_DOWN: return KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0, true);
case RELEASED_LEFT: return KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0, true);
case RELEASED_RIGHT: return KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0, true);
}
return null;
}
}
private PlayerEntity playerEntity;
private MonsterEntity monsterEntity;
private Timer timer;
private Set<PlayerAction> actions = new HashSet<PlayerAction>();
public MainPane() {
InputMap inputMap = getInputMap(WHEN_IN_FOCUSED_WINDOW);
ActionMap actionMap = getActionMap();
inputMap.put(InputKey.PRESSED_UP.getKeyStroke(), InputKey.PRESSED_UP);
inputMap.put(InputKey.PRESSED_DOWN.getKeyStroke(), InputKey.PRESSED_DOWN);
inputMap.put(InputKey.PRESSED_LEFT.getKeyStroke(), InputKey.PRESSED_LEFT);
inputMap.put(InputKey.PRESSED_RIGHT.getKeyStroke(), InputKey.PRESSED_RIGHT);
inputMap.put(InputKey.RELEASED_UP.getKeyStroke(), InputKey.RELEASED_UP);
inputMap.put(InputKey.RELEASED_DOWN.getKeyStroke(), InputKey.RELEASED_DOWN);
inputMap.put(InputKey.RELEASED_LEFT.getKeyStroke(), InputKey.RELEASED_LEFT);
inputMap.put(InputKey.RELEASED_RIGHT.getKeyStroke(), InputKey.RELEASED_RIGHT);
actionMap.put(InputKey.PRESSED_UP, new MoveAction(actions, PlayerAction.UP, true));
actionMap.put(InputKey.PRESSED_DOWN, new MoveAction(actions, PlayerAction.DOWN, true));
actionMap.put(InputKey.PRESSED_LEFT, new MoveAction(actions, PlayerAction.LEFT, true));
actionMap.put(InputKey.PRESSED_RIGHT, new MoveAction(actions, PlayerAction.RIGHT, true));
actionMap.put(InputKey.RELEASED_UP, new MoveAction(actions, PlayerAction.UP, false));
actionMap.put(InputKey.RELEASED_DOWN, new MoveAction(actions, PlayerAction.DOWN, false));
actionMap.put(InputKey.RELEASED_LEFT, new MoveAction(actions, PlayerAction.LEFT, false));
actionMap.put(InputKey.RELEASED_RIGHT, new MoveAction(actions, PlayerAction.RIGHT, false));
Dimension size = getPreferredSize();
Point center = new Point((size.width - 35) / 2, (size.height - 35) / 2);
playerEntity = new PlayerEntity(Color.BLUE, center);
monsterEntity = new MonsterEntity(Color.RED, new Point(size.width - 15, size.height - 15));
}
#Override
public void addNotify() {
super.addNotify();
if (timer != null) {
timer.stop();
}
timer = new Timer(5, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
performTick();
}
});
timer.start();
}
#Override
public void removeNotify() {
super.removeNotify();
if (timer != null) {
timer.stop();
}
}
#Override
public Dimension getPreferredSize() {
return new Dimension(400, 400);
}
protected void performTick() {
playerEntity.update(actions, getSize());
monsterEntity.moveTowards(playerEntity.getCenter());
repaint();
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
playerEntity.paint(g2d);
monsterEntity.paint(g2d);
g2d.dispose();
}
}
Movement (or input) is controlled through the key bindings API, this triggers a MoveAction which updates a centralised state repository (which is then passed to the PlayerEntity so it apply the state accordingly).
For simplicity, I've only used a single Action, but you could make a couple, one representing "press/activate" or "release/deactivate"
public class MoveAction extends AbstractAction {
private Set<PlayerAction> actions;
private PlayerAction action;
private boolean activate;
public MoveAction(Set<PlayerAction> directions, PlayerAction direction, boolean activate) {
this.actions = directions;
this.action = direction;
this.activate = activate;
}
#Override
public void actionPerformed(ActionEvent e) {
if (activate) {
actions.add(action);
} else {
actions.remove(action);
}
}
}
See How to Use Actions for more details about actions.
But why follow this workflow?!
It decouples and decentralises a lot of the workflows. In fact, if you really wanted to, you could also seperate out the Timer and "paint" workflows to seperate classes, further decoupling the classes.
Key bindings solve all the issues related to KeyListener weirdness. It also decouples the input - want to add touch controls/buttons, no worries, it's done via Actions. Want to add joystick/controllers, no worries, it's done via Actions.
Want more monsters?
Change:
private MonsterEntity monsterEntity;
to:
private List<MonsterEntity> monsterEntitys = new ArrayList<>(32);
Change:
monsterEntity = new MonsterEntity(Color.RED, new Point(size.width - 15, size.height - 15));
to:
monsterEntitys.add(new MonsterEntity(Color.RED, new Point(size.width - 15, size.height - 15)));
monsterEntitys.add(new MonsterEntity(Color.RED, new Point(0, 0)));
monsterEntitys.add(new MonsterEntity(Color.RED, new Point(size.width - 15, 0)));
monsterEntitys.add(new MonsterEntity(Color.RED, new Point(0, size.height - 15)));
Change:
monsterEntity.paint(g2d);
to:
for (MonsterEntity entity : monsterEntitys) {
entity.paint(g2d);
}
And now you have more monsters! Have fun with that!
Runnable example...
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.util.HashSet;
import java.util.Set;
import javax.swing.AbstractAction;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.KeyStroke;
import javax.swing.Timer;
public class Main {
public static void main(String[] args) {
new Main();
}
public Main() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
JFrame frame = new JFrame();
frame.add(new MainPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public enum PlayerAction {
UP, DOWN, LEFT, RIGHT;
}
public class MainPane extends JPanel {
private enum InputKey {
PRESSED_UP, PRESSED_DOWN, PRESSED_LEFT, PRESSED_RIGHT,
RELEASED_UP, RELEASED_DOWN, RELEASED_LEFT, RELEASED_RIGHT;
public KeyStroke getKeyStroke() {
switch (this) {
case PRESSED_UP: return KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0, false);
case PRESSED_DOWN: return KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0, false);
case PRESSED_LEFT: return KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0, false);
case PRESSED_RIGHT: return KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0, false);
case RELEASED_UP: return KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0, true);
case RELEASED_DOWN: return KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0, true);
case RELEASED_LEFT: return KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0, true);
case RELEASED_RIGHT: return KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0, true);
}
return null;
}
}
private PlayerEntity playerEntity;
private MonsterEntity monsterEntity;
private Timer timer;
private Set<PlayerAction> actions = new HashSet<PlayerAction>();
public MainPane() {
InputMap inputMap = getInputMap(WHEN_IN_FOCUSED_WINDOW);
ActionMap actionMap = getActionMap();
inputMap.put(InputKey.PRESSED_UP.getKeyStroke(), InputKey.PRESSED_UP);
inputMap.put(InputKey.PRESSED_DOWN.getKeyStroke(), InputKey.PRESSED_DOWN);
inputMap.put(InputKey.PRESSED_LEFT.getKeyStroke(), InputKey.PRESSED_LEFT);
inputMap.put(InputKey.PRESSED_RIGHT.getKeyStroke(), InputKey.PRESSED_RIGHT);
inputMap.put(InputKey.RELEASED_UP.getKeyStroke(), InputKey.RELEASED_UP);
inputMap.put(InputKey.RELEASED_DOWN.getKeyStroke(), InputKey.RELEASED_DOWN);
inputMap.put(InputKey.RELEASED_LEFT.getKeyStroke(), InputKey.RELEASED_LEFT);
inputMap.put(InputKey.RELEASED_RIGHT.getKeyStroke(), InputKey.RELEASED_RIGHT);
actionMap.put(InputKey.PRESSED_UP, new MoveAction(actions, PlayerAction.UP, true));
actionMap.put(InputKey.PRESSED_DOWN, new MoveAction(actions, PlayerAction.DOWN, true));
actionMap.put(InputKey.PRESSED_LEFT, new MoveAction(actions, PlayerAction.LEFT, true));
actionMap.put(InputKey.PRESSED_RIGHT, new MoveAction(actions, PlayerAction.RIGHT, true));
actionMap.put(InputKey.RELEASED_UP, new MoveAction(actions, PlayerAction.UP, false));
actionMap.put(InputKey.RELEASED_DOWN, new MoveAction(actions, PlayerAction.DOWN, false));
actionMap.put(InputKey.RELEASED_LEFT, new MoveAction(actions, PlayerAction.LEFT, false));
actionMap.put(InputKey.RELEASED_RIGHT, new MoveAction(actions, PlayerAction.RIGHT, false));
Dimension size = getPreferredSize();
Point center = new Point((size.width - 35) / 2, (size.height - 35) / 2);
playerEntity = new PlayerEntity(Color.BLUE, center);
monsterEntity = new MonsterEntity(Color.RED, new Point(size.width - 15, size.height - 15));
}
#Override
public void addNotify() {
super.addNotify();
if (timer != null) {
timer.stop();
}
timer = new Timer(5, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
performTick();
}
});
timer.start();
}
#Override
public void removeNotify() {
super.removeNotify();
if (timer != null) {
timer.stop();
}
}
#Override
public Dimension getPreferredSize() {
return new Dimension(400, 400);
}
protected void performTick() {
playerEntity.update(actions, getSize());
monsterEntity.moveTowards(playerEntity.getCenter());
repaint();
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
playerEntity.paint(g2d);
monsterEntity.paint(g2d);
g2d.dispose();
}
}
public class MoveAction extends AbstractAction {
private Set<PlayerAction> actions;
private PlayerAction action;
private boolean activate;
public MoveAction(Set<PlayerAction> directions, PlayerAction direction, boolean activate) {
this.actions = directions;
this.action = direction;
this.activate = activate;
}
#Override
public void actionPerformed(ActionEvent e) {
if (activate) {
actions.add(action);
} else {
actions.remove(action);
}
}
}
public interface Entity {
public void paint(Graphics2D g2d);
}
public static class MonsterEntity implements Entity {
protected static final int DELTA = 1;
private Rectangle bounds = new Rectangle(0, 0, 15, 15);
private Color fillColor;
public MonsterEntity(Color fillColor, Point location) {
this.fillColor = fillColor;
this.bounds.setLocation(location);
}
public Color getFillColor() {
return fillColor;
}
public Rectangle getBounds() {
return bounds;
}
public Point getCenter() {
return new Point((int)getBounds().getCenterX(), (int)getBounds().getCenterY());
}
public void moveTowards(Point target) {
Rectangle bounds = getBounds();
Point center = getCenter();
int xDelta = target.x < center.x ? -DELTA : DELTA;
int yDelta = target.y < center.y ? -DELTA : DELTA;
getBounds().setLocation(bounds.x + xDelta, bounds.y + yDelta);
}
#Override
public void paint(Graphics2D g2d) {
g2d.setColor(getFillColor());
g2d.fill(getBounds());
}
}
public static class PlayerEntity implements Entity {
protected static final int DELTA = 2;
private Rectangle bounds = new Rectangle(0, 0, 35, 35);
private Color fillColor;
public PlayerEntity(Color fillColor, Point location) {
this.fillColor = fillColor;
this.bounds.setLocation(location);
}
public Color getFillColor() {
return fillColor;
}
public Rectangle getBounds() {
return bounds;
}
public Point getCenter() {
return new Point((int)getBounds().getCenterX(), (int)getBounds().getCenterY());
}
public void update(Set<PlayerAction> actions, Dimension size) {
Rectangle currentBounds = getBounds();
int x = currentBounds.x;
int y = currentBounds.y;
if (actions.contains(PlayerAction.UP)) {
y -= DELTA;
}
if (actions.contains(PlayerAction.DOWN)) {
y += DELTA;
}
if (actions.contains(PlayerAction.LEFT)) {
x -= DELTA;
}
if (actions.contains(PlayerAction.RIGHT)) {
x += DELTA;
}
if (y < 0) {
y = 0;
}
if (y + currentBounds.height > size.height) {
y = size.height - currentBounds.height;
}
if (x < 0) {
x = 0;
}
if (x + currentBounds.width > size.width) {
x = size.width - currentBounds.width;
}
getBounds().setLocation(x, y);
}
#Override
public void paint(Graphics2D g2d) {
g2d.setColor(getFillColor());
g2d.fill(getBounds());
}
}
}
Other considerations...
Right now the speed/delta is actually really high. I would consider making use of the Shape API, using things like Point2D and Rectangle2D which provide double based properties instead of int, which would give away to reduce the delta values and slow down the entities.
See Working with Geometry for some more details

drawImage is not applicable for the arguments

Look I'm going to be up front about this. My assignment is due soon and i've spent way too many hours trying to fix this problem with no success at all. I'm essentially clueless at what the issue is and I really dont know where to look. I have 5 classes, I will try and post them all to ensure I get the answer, I am unable to change GameManager or Goal but I am allowed to change any other class.
The problem lines are this.canvasGraphics.drawImage(player.getCurrentImage() where drawImage says it isnt applicable for the arguments
and
this.enemies[i].getX() - (this.enemies[i].getCurrentImage().getWidth() / 2),
this.enemies[i].getY() - (this.enemies[i].getCurrentImage().getHeight() / 2), null);
where getWidth and getHeight show an almost identical error
thanks in advance
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Toolkit;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.image.BufferedImage;
import java.awt.Font;
import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
public class GameManager extends JFrame implements KeyListener {
private int canvasWidth;
private int canvasHeight;
private int borderLeft;
private int borderTop;
private BufferedImage canvas;
private Stage stage;
private Enemy[] enemies;
private Player player;
private Goal goal;
private Graphics gameGraphics;
private Graphics canvasGraphics;
private int numEnemies;
private boolean continueGame;
public static void main(String[] args) {
// During development, you can adjust the values provided in the brackets below
// as needed. However, your code must work with different/valid combinations
// of values.
int choice;
do{
GameManager managerObj = new GameManager(1920, 1080);
choice=JOptionPane.showConfirmDialog(null,"Play again?", "", JOptionPane.OK_CANCEL_OPTION);
}while(choice==JOptionPane.OK_OPTION);
System.exit(0);
}
public GameManager(int preferredWidth, int preferredHeight) {
int maxEnemies;
try{
maxEnemies=Integer.parseInt(JOptionPane.showInputDialog("How many enemies? (Default is 5)"));
if (maxEnemies<0)
maxEnemies=5;
}
catch (Exception e){
maxEnemies=5;
}
this.borderLeft = getInsets().left;
this.borderTop = getInsets().top;
Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
if (screenSize.width < preferredWidth)
this.canvasWidth = screenSize.width - getInsets().left - getInsets().right;
else
this.canvasWidth = preferredWidth - getInsets().left - getInsets().right;
if (screenSize.height < preferredHeight)
this.canvasHeight = screenSize.height - getInsets().top - getInsets().bottom;
else
this.canvasHeight = preferredHeight - getInsets().top - getInsets().bottom;
setSize(this.canvasWidth, this.canvasHeight);
setResizable(false);
setDefaultCloseOperation(EXIT_ON_CLOSE);
setVisible(true);
addKeyListener(this);
Random rng = new Random();
this.canvas = new BufferedImage(this.canvasWidth, this.canvasHeight, BufferedImage.TYPE_INT_RGB);
// Create a Stage object to hold the background images
this.stage = new Stage();
// Create a Goal object with its initial x and y coordinates
this.goal = new Goal((Math.abs(rng.nextInt()) % (this.canvasWidth)),
(Math.abs(rng.nextInt()) % this.canvasHeight));
// Create a Player object with its initial x and y coordinates
this.player = new Player((Math.abs(rng.nextInt()) % (this.canvasWidth)),
(Math.abs(rng.nextInt()) % this.canvasHeight));
// Create the Enemy objects, each with a reference to this (GameManager) object
// and their initial x and y coordinates.
this.numEnemies = maxEnemies;
this.enemies = new Enemy[this.numEnemies];
for (int i = 0; i < this.numEnemies; i++) {
this.enemies[i] = new Enemy(this, Math.abs(rng.nextInt()) % (this.canvasWidth),
Math.abs(rng.nextInt()) % this.canvasHeight);
}
this.gameGraphics = getGraphics();
this.canvasGraphics = this.canvas.getGraphics();
this.continueGame = true;
long gameStartTime=System.nanoTime();
while (this.continueGame) {
updateCanvas();
}
this.stage.setGameOverBackground();
double gameTime=(System.nanoTime()-gameStartTime)/1000000000.0;
updateCanvas();
this.gameGraphics.setFont(new Font(this.gameGraphics.getFont().getFontName(), Font.PLAIN, 50));
if (gameTime<1)
this.gameGraphics.drawString("Oops! Better luck next time...", this.canvasWidth/3, this.canvasHeight/2 - 50);
else
this.gameGraphics.drawString("You survived " + String.format("%.1f", gameTime)+ " seconds with "+this.numEnemies+" enemies!",
this.canvasWidth/4, this.canvasHeight/2 - 50);
return;
}
public void updateCanvas() {
long start = System.nanoTime();
this.goal.performAction();
// If the player is alive, this should move the player in the direction of the
// key that has been pressed
// Note: See keyPressed and keyReleased methods in the GameManager class.
this.player.performAction();
// If the enemy is alive, the enemy must move towards the Player. The Player object
// is obtained via the GameManager object that is given at the time of creating an Enemy
// object.
// Note: The amount that the enemy moves by must be much smaller than that of
// the player above or else the game becomes too hard to play.
for (int i = 0; i < this.numEnemies; i++) {
this.enemies[i].performAction();
}
if ((Math.abs(this.goal.getX() - this.player.getX()) < (this.goal.getCurrentImage().getWidth() / 2))
&& (Math.abs(this.goal.getY() - this.player.getY()) < (this.goal.getCurrentImage().getWidth() / 2))) {
for (int i = 0; i < this.numEnemies; i++) {
// Sets the image of the enemy to the "dead" image and sets its status to
// indicate dead
this.enemies[i].die();
}
// Sets the background of the stage to the finished game background.
this.stage.setGameOverBackground();
this.continueGame = false;
}
// If an enemy is close to the player or the goal, the player and goal die
int j = 0;
while (j < this.numEnemies) {
if ((Math.abs(this.player.getX() - this.enemies[j].getX()) < (this.player.getCurrentImage().getWidth() / 2))
&& (Math.abs(this.player.getY() - this.enemies[j].getY()) < (this.player.getCurrentImage().getWidth()
/ 2))) {
this.player.die();
this.goal.die();
this.stage.setGameOverBackground();
j = this.numEnemies;
this.continueGame = false;
}
else if ((Math.abs(this.goal.getX() - this.enemies[j].getX()) < (this.goal.getCurrentImage().getWidth() / 2))
&& (Math.abs(this.goal.getY() - this.enemies[j].getY()) < (this.goal.getCurrentImage().getWidth()
/ 2))) {
this.player.die();
this.goal.die();
this.stage.setGameOverBackground();
j = this.numEnemies;
this.continueGame = false;
}
j++;
}
try {
// Draw stage
this.canvasGraphics.drawImage(stage.getCurrentImage(), 0, 0, null);
// Draw goal
this.canvasGraphics.drawImage(this.goal.getCurrentImage(),
this.goal.getX() - (this.goal.getCurrentImage().getWidth() / 2),
this.goal.getY() - (this.goal.getCurrentImage().getHeight() / 2), null);
// Draw player
this.canvasGraphics.drawImage(player.getCurrentImage(),
this.player.getX() - (this.player.getCurrentImage().getWidth() / 2),
this.player.getY() - (this.player.getCurrentImage().getHeight() / 2), null);
// Draw enemies
for (int i = 0; i < this.numEnemies; i++) {
this.canvasGraphics.drawImage(this.enemies[i].getCurrentImage(),
this.enemies[i].getX() - (this.enemies[i].getCurrentImage().getWidth() / 2),
this.enemies[i].getY() - (this.enemies[i].getCurrentImage().getHeight() / 2), null);
}
} catch (Exception e) {
System.err.println(e.getMessage());
}
// Draw everything.
this.gameGraphics.drawImage(this.canvas, this.borderLeft, this.borderTop, this);
long end = System.nanoTime();
this.gameGraphics.setFont(new Font(this.gameGraphics.getFont().getFontName(), Font.PLAIN, 15));
this.gameGraphics.drawString("FPS: " + String.format("%2d", (int) (1000000000.0 / (end - start))),
this.borderLeft + 50, this.borderTop + 75);
return;
}
public Player getPlayer() {
return this.player;
}
public void keyPressed(KeyEvent ke) {
// Below, the setKey method is used to tell the Player object which key is
// currently pressed.
// The Player object must keep track of the pressed key and use it for
// determining the direction
// to move.
// Important: The setKey method in Player must not move the Player.
if (ke.getKeyCode() == KeyEvent.VK_LEFT)
this.player.setKey('L', true);
if (ke.getKeyCode() == KeyEvent.VK_RIGHT)
this.player.setKey('R', true);
if (ke.getKeyCode() == KeyEvent.VK_UP)
this.player.setKey('U', true);
if (ke.getKeyCode() == KeyEvent.VK_DOWN)
this.player.setKey('D', true);
if (ke.getKeyCode() == KeyEvent.VK_ESCAPE)
this.continueGame = false;
return;
}
#Override
public void keyReleased(KeyEvent ke) {
// Below, the setKey method is used to tell the Player object which key is
// currently released.
// The Player object must keep track of the pressed key and use it for
// determining the direction
// to move.
// Important: The setKey method in Player must not move the Player.
if (ke.getKeyCode() == KeyEvent.VK_LEFT)
this.player.setKey('L', false);
if (ke.getKeyCode() == KeyEvent.VK_RIGHT)
this.player.setKey('R', false);
if (ke.getKeyCode() == KeyEvent.VK_UP)
this.player.setKey('U', false);
if (ke.getKeyCode() == KeyEvent.VK_DOWN)
this.player.setKey('D', false);
return;
}
#Override
public void keyTyped(KeyEvent ke) {
return;
}
}
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import java.util.*;
public class Goal {
private int x;
private int y;
private BufferedImage imageCurrent;
private BufferedImage imageRunning;
private BufferedImage imageOver;
private int stepSize;
private Random rng; // Tip: Code that students write must not use randomness
public Goal(int x, int y) {
try {
this.imageRunning = ImageIO.read(new File("goal-alive.png"));
this.imageOver = ImageIO.read(new File("goal-dead.png"));
} catch (IOException e) {
e.printStackTrace();
}
this.x = x;
this.y = y;
this.stepSize = 10;
this.rng = new Random(x + y); // Tip: Code that students write (elsewhere) must not use any randomness.
this.imageCurrent = this.imageRunning;
return;
}
public void performAction() {
// The code below shows how the Goal can be moved by manipulating its x and y
// coordinates.
// Tip: Code that students write (elsewhere) must not use any randomness.
this.x += this.rng.nextInt() % stepSize;
this.y += this.rng.nextInt() % stepSize;
return;
}
public int getY() {
return this.y;
}
public int getX() {
return this.x;
}
public BufferedImage getCurrentImage() {
return this.imageCurrent;
}
public void die() {
this.imageCurrent = this.imageOver;
return;
}
}
import java.awt.Image;
public class Enemy {
private Image CurrentImage;
private int x;
private int y;
public Enemy(GameManager gameManager, int x, int y) {
}
public void performAction() {
}
public void die() {
}
public int getX() {
return this.x;
}
public int getY() {
return this.y;
}
public Image getCurrentImage() {
return CurrentImage;
}
}
import java.awt.Dimension;
public class Player {
private Dimension CurrentImage;
private int x;
private int y;
public Player(int x1, int y1) {
}
public void performAction() {
}
public int getX() {
return this.x;
}
public int getY() {
return this.y;
}
public Dimension getCurrentImage() {
return CurrentImage;
}
public void die() {
}
public void setKey(char c, boolean b) {
}
}
import java.awt.Image;
public class Stage {
public void setGameOverBackground() {
}
public Image getCurrentImage() {
return null;
}
}

Player.getCurrentImage() returns a Dimension, not an Image.

How do I paint multiple objetcs that move at different speeds in Java?

I am working on homework for class, and its late because I can't seem to understand the material despite all the research that I am doing. I am a beginner and do not know much in the way of java. Also, this is my first post so please be forgiving when you are reading this.
I am building on source code from my textbook, which I updated recently for past homework, but now I am trying to generate a class that draws multiple squares and moves those objects independently and at different speeds. They will all need to rebound off the walls as well. I followed the instructions and created two arrays that will hold the random x and y values between 1 and 10. However, I struggle with arrays and I am sure that I am not doing it correctly. So, I would love some feedback to see if I have it set up correctly.
I have a the jpanel pulling up and drawing, and as long as there is 1 square it is working fine bouncing off the walls, but things change when I draw more than one. The do not move independently and they also share the same speed. Some even disappear from time to time. This has really thrown me off. I appreciate any help!
In short, I am trying to paint new squares that all travel in different directions and at different speeds. Per the instructions we are suppose create and use a two arrays that handle the x and y values.
Here is what I have so far:
public class DotsPanel extends JPanel
{
private int delay = 15;
private final int SIZE = 7, IMAGE_SIZE = 3; // radius of each dot
private Timer timer;
private int x, y, i;
private ArrayList<Point> pointList;
static int [] xarray = new int [1000];
static int [] yarray = new int [1000];
Random rand = new Random();
//-----------------------------------------------------------------
// Constructor: Sets up this panel to listen for mouse events.
//-----------------------------------------------------------------
public DotsPanel()
{
pointList = new ArrayList<Point>();
int [] xarray = new int [1000];
int [] yarray = new int [1000];
timer = new Timer(delay, new ReboundListener());
addMouseListener (new DotsListener());
addMouseMotionListener (new DotsListener());
setBackground(Color.gray);
setPreferredSize(new Dimension(700, 500));
for(int i = 0; i < xarray.length; i++)
{
xarray[i] = rand.nextInt(7);
yarray[i] = rand.nextInt(7);
}
timer.start();
}
//-----------------------------------------------------------------
// Draws all of the dots stored in the list.
//-----------------------------------------------------------------
public void paintComponent(Graphics page)
{
super.paintComponent(page);
page.setColor(Color.BLUE);
for (Point spot : pointList)
{
page.fillRect(spot.x-SIZE, spot.y-SIZE, 25, 25);
page.drawString("Count: " + pointList.size(), 5, 15);
}
}
//*****************************************************************
// Represents the listener for mouse events.
//*****************************************************************
private class DotsListener implements MouseListener, MouseMotionListener
{
//--------------------------------------------------------------
// Adds the current point to the list of points and redraws
// the panel whenever the mouse button is pressed.
//--------------------------------------------------------------
public void mousePressed(MouseEvent event)
{
pointList.add(event.getPoint());
repaint();
}
public void mouseDragged(MouseEvent event)
{
// initially I had two xarray and yarray in here just like in
// mouseClicked
// but it did not change anything when removed
}
//--------------------------------------------------------------
// Provide empty definitions for unused event methods.
//--------------------------------------------------------------
public void mouseClicked(MouseEvent event)
{
xarray[i] = rand.nextInt(7);
yarray[i] = rand.nextInt(7);
}
public void mouseReleased(MouseEvent event) {}
public void mouseEntered(MouseEvent event) {}
public void mouseExited(MouseEvent event) {}
public void mouseMoved(MouseEvent e) {}
}
private class ReboundListener implements ActionListener
{
//--------------------------------------------------------------
// Updates the position of the image and possibly the direction
// of movement whenever the timer fires an action event.
//--------------------------------------------------------------
public void actionPerformed(ActionEvent event)
{
for (Point spot : pointList)
{
spot.x += xarray[i];
spot.y += yarray[i];
if (spot.x <= 0 || spot.x >= 700)
xarray[i] = xarray[i] * -1;
if (spot.y <= 0 || spot.y >= 500)
yarray[i] = yarray[i] * -1;
repaint();
}
}
}
}

However, I struggle with arrays and I am sure that I am not doing it correctly.
I wouldn't use Arrays.
Instead, have a Ball object manage its own state. Then you can have different color, speed, size etc for each Ball. Then when the Timer fires you just calculate the new position and repaint the Ball.
Here is an example to get you started:
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import java.util.*;
import javax.swing.*;
import javax.swing.Timer;
public class BallAnimation4
{
private static void createAndShowUI()
{
BallPanel panel = new BallPanel();
JFrame frame = new JFrame("BallAnimation4");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add( panel );
frame.setSize(800, 600);
frame.setLocationRelativeTo( null );
//frame.setExtendedState(JFrame.MAXIMIZED_BOTH);
frame.setVisible( true );
panel.addBalls(5);
panel.startAnimation();
}
public static void main(String[] args)
{
EventQueue.invokeLater(new Runnable()
{
public void run()
{
createAndShowUI();
}
});
}
}
class BallPanel extends JPanel implements ActionListener
{
private ArrayList<Ball> balls = new ArrayList<Ball>();
public BallPanel()
{
setLayout( null );
setBackground( Color.BLACK );
}
public void addBalls(int ballCount)
{
Random random = new Random();
for (int i = 0; i < ballCount; i++)
{
Ball ball = new Ball();
ball.setRandomColor(true);
ball.setLocation(random.nextInt(getWidth()), random.nextInt(getHeight()));
ball.setMoveRate(32, 32, 1, 1, true);
// ball.setMoveRate(16, 16, 1, 1, true);
ball.setSize(32, 32);
balls.add( ball );
}
}
#Override
public void paintComponent(Graphics g)
{
super.paintComponent(g);
for (Ball ball: balls)
{
ball.draw(g);
}
}
public void startAnimation()
{
Timer timer = new Timer(75, this);
timer.start();
}
public void actionPerformed(ActionEvent e)
{
move();
repaint();
}
private void move()
{
for (Ball ball : balls)
{
ball.move(this);
}
}
class Ball
{
public Color color = Color.BLACK;
public int x = 0;
public int y = 0;
public int width = 1;
public int height = 1;
private int moveX = 1;
private int moveY = 1;
private int directionX = 1;
private int directionY = 1;
private int xScale = moveX;
private int yScale = moveY;
private boolean randomMove = false;
private boolean randomColor = false;
private Random myRand = null;
public Ball()
{
myRand = new Random();
setRandomColor(randomColor);
}
public void move(JPanel parent)
{
int iRight = parent.getSize().width;
int iBottom = parent.getSize().height;
x += 5 + (xScale * directionX);
y += 5 + (yScale * directionY);
if (x <= 0)
{
x = 0;
directionX *= (-1);
xScale = randomMove ? myRand.nextInt(moveX) : moveX;
if (randomColor) setRandomColor(randomColor);
}
if (x >= iRight - width)
{
x = iRight - width;
directionX *= (-1);
xScale = randomMove ? myRand.nextInt(moveX) : moveX;
if (randomColor) setRandomColor(randomColor);
}
if (y <= 0)
{
y = 0;
directionY *= (-1);
yScale = randomMove ? myRand.nextInt(moveY) : moveY;
if (randomColor) setRandomColor(randomColor);
}
if (y >= iBottom - height)
{
y = iBottom - height;
directionY *= (-1);
yScale = randomMove ? myRand.nextInt(moveY) : moveY;
if (randomColor) setRandomColor(randomColor);
}
}
public void draw(Graphics g)
{
g.setColor(color);
g.fillOval(x, y, width, height);
}
public void setColor(Color c)
{
color = c;
}
public void setLocation(int x, int y)
{
this.x = x;
this.y = y;
}
public void setMoveRate(int xMove, int yMove, int xDir, int yDir, boolean randMove)
{
this.moveX = xMove;
this.moveY = yMove;
directionX = xDir;
directionY = yDir;
randomMove = randMove;
}
public void setRandomColor(boolean randomColor)
{
this.randomColor = randomColor;
switch (myRand.nextInt(3))
{
case 0: color = Color.BLUE;
break;
case 1: color = Color.GREEN;
break;
case 2: color = Color.RED;
break;
default: color = Color.BLACK;
break;
}
}
public void setSize(int width, int height)
{
this.width = width;
this.height = height;
}
}
}
Since your Arrays only contain the Point you want to paint you don't have any information about the speed each point should be moved at. The best you could do is create a random amount each point should be moved each time its location is changed. This would give erratic movement as each time you move a point the distance would be random.
If you want more constant speed then you would need to create a second Array to contain the distance each point should move every time.
This starts to get messy creating a new Array every time you want a new property to be unique for the object you want to paint. That is why the approach to create a custom Object with multiple properties is easier to manage.

Change ball color when colliding

I'm making an java app (for exercise) where there must be a panel and 2 buttons.
Each time you press the start button a ball must be displayed and it moves based on thread. The user can display all the way up to 10 independent balls.
By pressing the stop button, 1 ball must be removed with each time the stop button is pressed (example, when there is 4 balls, the user must press 4 times stop button to remove all the balls independently)
All the x- and y coordinates of the balls must be stored in a Matrix
When 1 or more ball(s) are colliding with each other, only the colliding balls must change color from red to blue
Ok I'm almost done with it completely ( from point 1 to 4 ), but here comes my problem. When a ball is colliding with another, instead of changing the colors of the colliding balls to blue, my code is changing all the balls color from red to blue. I know that my error lies at the new Balls().setColor(Color.Blue), but I have no idea how to change only the colliding balls.
Below follows a screen shot of the java app and the code.
Can anyone help me with this headache?
Printscreen:
source code:
import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;`
public class BouncingBalls extends JPanel implements ActionListener {
protected List<Ball> balls = new ArrayList<Ball>(10);
private final Container container;
private final DrawCanvas canvas;
private int canvasWidth;
private int canvasHeight;
public JButton start, stop;
int [][] coords= new int[11][2];
int ammountOfBalls = 0;
static Color clr= Color.RED;
public static int random(int maxRange) {
return (int) Math.round((Math.random() * maxRange));
}
public BouncingBalls(int width, int height) {
setLayout(new FlowLayout());
start= new JButton("start");
start.addActionListener(this);
stop= new JButton("stop");
stop.addActionListener(this);
add(start);
add(stop);
add(new JLabel(""));
container = new Container();
canvasWidth = width;
canvasHeight = height;
canvas = new DrawCanvas();
this.setLayout(new FlowLayout());
this.add(canvas);
start();
}
public void start() {
Thread t = new Thread() {
#Override
public void run() {
while (true) {
update();
getPositions();
collisionDetection();
repaint();
try {
Thread.sleep(30);
} catch (InterruptedException e) {
}
}
}
private void collisionDetection() {
// The algorithm that detects collision
for(int i=0;i<ammountOfBalls;i++){
for(int j=i+1; j<ammountOfBalls; j++){
if(collisionMethod(i,j)){ // my collision method
//HOW DO I CHANGE ONLY THE COLLIDING BALLS COLOR HERE????
new Ball().setColor(Color.BLUE); // this line here changes the color of all the balls on the panel
System.out.println("Its a hit");
}
}
}
}
private void getPositions() {
int row=0;
for (Ball ball : balls) {
int x =ball.getXPosition();
int y =ball.getYPosition();
coords[row][0]=x;
coords[row][1]=y;
row++;
}
}
private boolean collisionMethod(int i, int j) {
float xd = coords[i][0]-coords[j][0];
float yd=coords[i][1]-coords[j][1];
float radius= new Ball().ballRadius;
float sqrRadius= radius * radius;
float distSqr= (xd * xd) + (yd * yd);
if(distSqr <= sqrRadius)
return true;
return false;
}
};
t.start();
}
public void update() {
for (Ball ball : balls) {
ball.move(container);
}
}
#Override
public void actionPerformed(ActionEvent e) {
if(e.getSource() == start){
if(ammountOfBalls < 10){
// to limit the ammount of balls to 10
balls.add(new Ball());
ammountOfBalls++;
}
}
else if( e.getSource() == stop){
if(ammountOfBalls > 0){
ammountOfBalls --;
balls.remove(ammountOfBalls);
}
}
}
class DrawCanvas extends JPanel {
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
container.draw(g);
for (Ball ball : balls) {
ball.draw(g);
}
}
#Override
public Dimension getPreferredSize() {
return (new Dimension(700, 400));
}
}
public static void main(String[] args) {
JFrame f = new JFrame("Bouncing Balls");
f.setDefaultCloseOperation(f.EXIT_ON_CLOSE);
f.setPreferredSize(new Dimension(800,500));
f.setContentPane(new BouncingBalls(800,800));
f.pack();
f.setVisible(true);
}
public static class Ball {
public int random(int maxRange) {
return (int) Math.round(Math.random() * maxRange);
}
int x = random(700); // method to get random coords for the x-value
int y = random(400); // method to get random coords for the y-value ...... these are used to get random positions for the balls instead of only static
int xMovement = 10;
int yMovement = 10;
int ballRadius = 20;
int i = 0;
public Color getColor(){
return clr;
}
public Color setColor(Color color){
clr=color;
return clr;
}
public void draw(Graphics g) {
g.setColor(getColor());
g.fillOval(x,y,ballRadius,ballRadius);
}
public int getXPosition(){
return x;
}
public int getYPosition(){
return y;
}
public void move(Container container) {
x += xMovement;
y += yMovement;
if (x - ballRadius < 0) {
xMovement = -xMovement;
x = ballRadius;
}
else if (x + ballRadius > 700) {
xMovement = -xMovement;
x = 700 - ballRadius;
}
if (y - ballRadius < 0) {
yMovement = -yMovement;
y = ballRadius;
}
else if (y + ballRadius > 400) {
yMovement = -yMovement;
y = 400 - ballRadius;
}
}
}
public static class Container {
private static final int hightPanel = 800;
private static final int widthPanel= 800;
public void draw(Graphics g) {
g.setColor(Color.WHITE);
g.fillRect(0, 0, widthPanel, hightPanel);
}
}
}
`

You have defined clr as a static field of your application. When your Ball class calls setColor() you are changing the value of clr to blue... and then any Ball that calls getColor() will see that clr is blue.
Solution: Don't make clr an application-wide static field. Define it in the Ball class as a non-static field, so each Ball has its own color.

Collision detection using plain arrays and rectangles--java

I am almost done with my first little java game for my final project. It is a sidescroller where you have to shoot/avoid asteroids. My last problem is figuring out how to make my array of asteroids collide with the player's lasers. Here's what I have so far, there's an "AWT-EventQueue-0" java.lang.NullPointerException" on line 137, that I can't deal with. Any help is appreciated.
Edit: I added in my other classes, I realize it would be hard to judge the functionality of my code if I didn't show you where it came from.
package ShooterGame;
import java.applet.Applet;
import java.applet.AudioClip;
import java.awt.*;
import java.awt.event.*;
import java.util.ArrayList;
import java.util.Random;
import javax.swing.*;
public class Board extends JPanel implements ActionListener
{
Enemy[] baddies = new Enemy[10000];
Player p;
Image img;
int y;
Timer time;
boolean lost = false;
static Font font = new Font("SanSerif", Font.BOLD, 24);
public AudioClip theme, bang, laser;
static ArrayList<Enemy> enemies;
public static int score = 0;
public static int lives = 5;
public Board()
{
p = new Player();
addKeyListener(new ActionListener());
setFocusable(true);
ImageIcon i = new ImageIcon("images/background.png");
img = i.getImage();
time = new Timer(5, this);
time.start();
for(int j = 0; j < baddies.length; j++)
{
Random ran = new Random();
y = ran.nextInt(365)+1;
baddies[j]= new Enemy((100*j + 700), y, "images/asteroid.gif");
}
theme = Applet.newAudioClip(getClass().getResource("theme.mid"));
theme.play();
bang = Applet.newAudioClip(getClass().getResource("bang.wav"));
}
public void actionPerformed(ActionEvent e)
{
checkCollisions();
ArrayList<?> bullets = Player.getBullets();
for(int i = 0; i < bullets.size(); i++)
{
Bullet b = (Bullet)bullets.get(i);
if(b.isVisible() == true)
{
b.move();
}
else
{
bullets.remove(i);
}
}
p.move();
for(int i = 0; i < baddies.length; i++)
{
if(p.x > 400)
{
baddies[i].move(p.getdx());
}
}
repaint();
}
public void paint(Graphics g)
{
super.paint(g);
Graphics2D g2d = (Graphics2D) g;
if(lost)
{
g2d.drawString("You Lose!", 300, 300);
}
if((p.getX() - 590) % 2400 == 0 || (p.getX() - 590) % 2400 == 1)
{
p.nx = 0;
}
if((p.getX() - 1790) % 2400 == 0 ||(p.getX() - 1790) % 2400 == 1)
{
p.nx2 = 0;
}
g2d.drawImage(img, 685-p.nx2, 0, null);
if(p.getX() >= 590)
{
g2d.drawImage(img, 685-p.nx, 0, null);
}
g2d.drawImage(p.getImage(), p.edge, p.getY(), null);
ArrayList<?> bullets = Player.getBullets();
for(int i = 0; i < bullets.size(); i++)
{
Bullet b = (Bullet)bullets.get(i);
g2d.drawImage(b.getImg(), b.getX(), b.getY(), null);
}
for(int i = 0; i < baddies.length; i++)
{
if(baddies[i].isAlive == true)
{
g2d.drawImage(baddies[i].getImg(), baddies[i].getX(), baddies[i].getY(), null);
}
}
g2d.setColor(Color.white);
g2d.drawString("Score: " + score, 0, 320);
g2d.drawString("Lives: " + lives, 80, 320);
}
public void checkCollisions()
{
Rectangle[] rect = new Rectangle[baddies.length];
for(int i = 0; i < baddies.length; i++)
{
Enemy e = (Enemy)baddies[i];
rect[i] = e.getBounds();
}
ArrayList<?> bullets = Player.getBullets();
for (int i = 0; i < bullets.size(); i++)
{
Bullet b = (Bullet) bullets.get(i);
Rectangle b1 = b.getBounds();
if (rect[i].intersects(b1) && baddies[i].isAlive())
{
score++;
baddies[i].isAlive = false;
baddies[i].isVisible = false;
bang.play();
}
Rectangle h = p.getBounds();
if (h.intersects(rect[i]))
{
if(baddies[i].isAlive() == true)
{
lives--;
if(lives < 0)
{
lost = true;
theme.stop();
System.exit(1);
}
}
}
}
}
private class ActionListener extends KeyAdapter
{
public void keyReleased(KeyEvent e)
{
p.keyReleased(e);
}
public void keyPressed(KeyEvent e)
{
p.keyPressed(e);
}
}
}
Enemy
package ShooterGame;
import java.awt.*;
import javax.swing.ImageIcon;
public class Enemy
{
int x, y;
Image img;
boolean isAlive = true;
boolean isVisible = true;
public Enemy(int startX, int startY, String location)
{
x = startX;
y = startY;
ImageIcon l = new ImageIcon(location);
img = l.getImage();
}
public Rectangle getBounds()
{
return new Rectangle(x, y, 60, 60);
}
public int getX()
{
return x;
}
public int getY()
{
return y;
}
public boolean isAlive()
{
return isAlive;
}
public boolean isVisible()
{
return isVisible;
}
public Image getImg()
{
return img;
}
public void move(int dx)
{
x = x - dx;
}
}
Bullet
package ShooterGame;
import java.applet.Applet;
import java.awt.*;
import javax.swing.ImageIcon;
import java.applet.AudioClip;
public class Bullet
{
int x, y;
Image img;
boolean visible;
public Bullet(int startX, int startY)
{
x = startX;
y = startY;
ImageIcon newBullet = new ImageIcon("images/bullet.gif");
img = newBullet.getImage();
visible = true;
}
public Rectangle getBounds()
{
return new Rectangle(x, y, 9, 5);
}
public int getX()
{
return x;
}
public int getY()
{
return y;
}
public Image getImg()
{
return img;
}
public boolean isVisible()
{
return visible;
}
public void move()
{
x = x + 2;
if(x > 700)
{
visible = false;
}
}
public void setVisible(boolean isVisible)
{
visible = isVisible;
}
}
Player
package ShooterGame;
import java.applet.Applet;
import java.applet.AudioClip;
import java.awt.*;
import java.awt.event.KeyEvent;
import java.util.ArrayList;
import javax.swing.ImageIcon;
public class Player
{
int x, dx, y, dy, nx2, nx, edge, ceiling;
Image player;
ImageIcon ib = new ImageIcon("images/player1back.gif");
ImageIcon i = new ImageIcon("images/playerstill.gif");
ImageIcon f = new ImageIcon("images/playerforward.gif");
ImageIcon up = new ImageIcon("images/playerup.gif");
ImageIcon down = new ImageIcon("images/playerdown.gif");
public AudioClip laser;
static ArrayList<Bullet> bullets;
public Player()
{laser = Applet.newAudioClip(getClass().getResource("laser.wav"));
player = ib.getImage();
x = 75;
nx = 0;
nx2 = 685;
y = 172;
edge = 150;
ceiling = 0;
bullets = new ArrayList<Bullet>();
}
public static ArrayList<Bullet> getBullets()
{
return bullets;
}
public void fire()
{
Bullet z = new Bullet((edge + 60), (y+17));
bullets.add(z);
}
public Rectangle getBounds()
{
return new Rectangle(edge, y, 43, 39);
}
public void move()
{
y = y + dy;
if(y < ceiling)
{
y = ceiling;
}
if(y > 290)
{
y = 290;
}
if(dx != -1)
{
if(edge + dx <= 151)
{
edge = edge + dx;
}
else
{
x = x + dx;
nx2 = nx2 + dx;
nx = nx + dx;
}
}
else
{
if(edge + dx > 0)
{
edge = edge + dx;
}
}
}
public int getX()
{
return x;
}
public int getdx()
{
return dx;
}
public int getY()
{
return y;
}
public Image getImage()
{
return player;
}
public void keyPressed(KeyEvent e)
{
int key = e.getKeyCode();
if(key == KeyEvent.VK_RIGHT)
{
dx = 2;
player = f.getImage();
}
if(key == KeyEvent.VK_UP)
{
dy = -1;
player = up.getImage();
}
if(key == KeyEvent.VK_DOWN)
{
dy = 1;
player = down.getImage();
}
if(key == KeyEvent.VK_SPACE)
{
fire();
laser.play();
}
}
public void keyReleased(KeyEvent e)
{
int key = e.getKeyCode();
if(key == KeyEvent.VK_RIGHT)
{
dx = 1;
player = ib.getImage();
}
if(key == KeyEvent.VK_UP)
{
dy = 0;
player = ib.getImage();
}
if(key == KeyEvent.VK_DOWN)
{
dy = 0;
player = ib.getImage();
}
}
}
Frame
package ShooterGame;
import javax.swing.*;
public class Frame
{
public AudioClip theme;
public Frame()
{
JFrame frame = new JFrame();
frame.add(new Board());
frame.setTitle("SideShooter");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(700,365);
frame.setVisible(true);
frame.setLocationRelativeTo(null);
}
public static void main(String[] args)
{
new Frame();
}
}

Ok, so the problem is the line mentioned in the other answer, but I believe it is that all the enemies may not be initialised before it checks collisions. Because you are making 10000 of them to start with, I think your action performed method may be checking collisions before they have all be created.
One thing to try could be to bring down the amount of enemies you have and see if it still keeps happening, try 100 or 1000, but this still won't fix the issue.
You really want to be change your game to run in it's own loop though, at the moment you are only checking collisions when the player performs an action. so if the player stops moving, no collision detection...
I would suggest that you find a book called 'Killer Game Programming in Java', there are free ebook version, and just read the first 2 chapters about making a game loop. The book is a bit old, but the basics of the loop are very good.
This question here also contains a very simple loop, and some suggestions in the comments about how to make it better.

The error is on the line
rect[i] = e.getBounds();
Are you not initializing the bounds of your Enemy class correctly? Alternatively, the Enemy you pulled out of the array could be null.

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