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As a self-project, I'm trying to make the game 'Asteroids'.
Currently, I'm stuck on trying to figure out how to make it so the lasers fired from my ship appear from the tip of the ship. So far, I've tried experimenting with using the Shape object's .getBounds2D().getX() methods, but because getBounds2D() draws a rectangle around the polygon, the lasers end up appearing from the corner of the imaginary 'box' around my Polygon ship.
Here's a gif of what I have so far.
Is there a way to 'get' a specific point from a Shape object; where, in this case, that specific point is the tip of the ship.
Main Class:
public class AsteroidGame implements ActionListener, KeyListener{
public static AsteroidGame game;
public Renderer renderer;
public boolean keyDown = false;
public int playerAngle = 0;
public boolean left = false;
public boolean right = false;
public boolean go = false;
public boolean back = false;
public boolean still = true;
public double angle = 0;
public int turnRight = 5;
public int turnLeft = -5;
public Shape transformed;
public ArrayList<Laser> lasers;
public ArrayList<Shape> transformedLasers;
public final int WIDTH = 1400;
public final int HEIGHT = 800;
public Ship ship;
public Rectangle shipHead;
public Shape shipHeadTrans;
public Point headPoint;
public AffineTransform transform = new AffineTransform();
public AffineTransform lasTransform = new AffineTransform();
public AffineTransform headTransform = new AffineTransform();
public AsteroidGame(){
JFrame jframe = new JFrame();
Timer timer = new Timer(20, this);
renderer = new Renderer();
jframe.add(renderer);
jframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
jframe.setSize(WIDTH, HEIGHT);
jframe.setVisible(true);
jframe.addKeyListener(this);
jframe.setResizable(false);
int xPoints[] = {800, 780, 800, 820};
int yPoints[] = {400, 460, 440, 460};
//(800, 400) is the initial location of the 'tip' of the ship'.
headPoint = new Point(800, 400);
lasers = new ArrayList<Laser>();
transformedLasers = new ArrayList<Shape>();
ship = new Ship(xPoints, yPoints, 4, 0);
transformed = transform.createTransformedShape(ship);
shipHead = new Rectangle(headPoint);
shipHeadTrans = transform.createTransformedShape(shipHead);
//shipHeadTrans.getBounds2D().
timer.start();
}
public void repaint(Graphics g){
g.setColor(Color.BLACK);
g.fillRect(0, 0, WIDTH, HEIGHT);
Graphics2D g2d = (Graphics2D)g;
//drawing the ship
g2d.setColor(Color.WHITE);
g2d.draw(transformed);
//drawing lasers
g2d.setColor(Color.RED);
for (int i = 0; i < transformedLasers.size(); i++){
System.out.println(i);
g2d.draw(transformedLasers.get(i));
}
}
public void actionPerformed(ActionEvent arg0) {
// TODO Auto-generated method stub
/*The for if and else if statements are just to send the ship
* to the other side of the canvas if it ever leaves the screen
*/
if (transformed.getBounds2D().getMinX() > WIDTH){
double tempAng = ship.getAng();
double diff = 90-tempAng;
transform.rotate(Math.toRadians(diff), ship.getCenterX(), ship.getCenterY());
transform.translate(0,WIDTH);
transform.rotate(Math.toRadians(-diff), ship.getCenterX(), ship.getCenterY());
}
else if (transformed.getBounds2D().getX() < 0){
double tempAng = ship.getAng();
double diff = 90-tempAng;
transform.rotate(Math.toRadians(diff), ship.getCenterX(), ship.getCenterY());
transform.translate(0,-WIDTH);
transform.rotate(Math.toRadians(-diff), ship.getCenterX(), ship.getCenterY());
}
else if (transformed.getBounds2D().getY() > HEIGHT){
double tempAng = ship.getAng();
double diff = 180-tempAng;
transform.rotate(Math.toRadians(diff), ship.getCenterX(), ship.getCenterY());
transform.translate(0,HEIGHT);
transform.rotate(Math.toRadians(-diff), ship.getCenterX(), ship.getCenterY());
}
else if (transformed.getBounds2D().getY() < 0){
double tempAng = ship.getAng();
double diff = 180-tempAng;
transform.rotate(Math.toRadians(diff), ship.getCenterX(), ship.getCenterY());
transform.translate(0,-HEIGHT);
transform.rotate(Math.toRadians(-diff), ship.getCenterX(), ship.getCenterY());
}
if (right){
ship.right();
//rotating the ship
transform.rotate(Math.toRadians(turnRight), ship.getCenterX(), ship.getCenterY());
//rotating the 'tip' of the ship.
headTransform.rotate(Math.toRadians(turnRight), ship.getCenterX(), ship.getCenterY());
}
else if (left){
ship.left();
//rotating the ship
transform.rotate(Math.toRadians(turnLeft), ship.getCenterX(), ship.getCenterY());
//rotating the 'tip' of the ship
headTransform.rotate(Math.toRadians(turnLeft), ship.getCenterX(), ship.getCenterY());
}
if (go){
ship.go();
}
else if (back){
ship.reverse();
}
//moving and shaping each individual laser that had been shot
for (int i = 0; i < transformedLasers.size(); i++){
lasers.get(i).move();
lasTransform = new AffineTransform();
lasTransform.rotate(Math.toRadians(lasers.get(i).getAng()), transformed.getBounds2D().getX(), transformed.getBounds2D().getY());
transformedLasers.set(i, lasTransform.createTransformedShape(lasers.get(i)));
}
//moving the ship
ship.move();
//moving the 'tip'
shipHead.y -= ship.getSpeed();
transformed = transform.createTransformedShape(ship);
shipHeadTrans = headTransform.createTransformedShape(shipHead);
renderer.repaint();
}
//defining a new laser
public void fireLaser(){
Laser tempLaser = new Laser((int)transformed.getBounds2D().getX(), (int)transformed.getBounds2D().getY(), 5, 10, ship.getAng());
lasers.add(tempLaser);
lasTransform = new AffineTransform();
lasTransform.rotate(Math.toRadians(ship.getAng()), transformed.getBounds2D().getX(), transformed.getBounds2D().getY());
transformedLasers.add(lasTransform.createTransformedShape(tempLaser));
}
public static void main(String[] args){
game = new AsteroidGame();
}
#Override
public void keyPressed(KeyEvent e) {
// TODO Auto-generated method stub
if (e.getKeyCode() == KeyEvent.VK_RIGHT){
right = true;
keyDown = true;
}else if (e.getKeyCode() == KeyEvent.VK_LEFT){
left = true;
keyDown = true;
}
else if (e.getKeyCode() == KeyEvent.VK_UP){
go = true;
}
else if (e.getKeyCode() == KeyEvent.VK_DOWN){
back = true;
}
//fire laser
if (e.getKeyCode() == KeyEvent.VK_SPACE){
fireLaser();
}
}
#Override
public void keyReleased(KeyEvent e) {
// TODO Auto-generated method stub
if (e.getKeyCode() == KeyEvent.VK_RIGHT){
right = false;
}
if (e.getKeyCode() == KeyEvent.VK_LEFT){
left = false;
}
if (e.getKeyCode() == KeyEvent.VK_UP){
go = false;
}
if (e.getKeyCode() == KeyEvent.VK_DOWN){
back = false;
}
still = true;
keyDown = false;
}
#Override
public void keyTyped(KeyEvent e) {
// TODO Auto-generated method stub
}
Ship Class (I don't think it's relevant though)
package asteroidGame;
import java.awt.Polygon;
import java.util.Arrays;
public class Ship extends Polygon{
/**
*
*/
private double currSpeed = 0;
private static final long serialVersionUID = 1L;
public double angle;
public int[] midX;
public int[] midY;
public Ship(int[] x, int[] y, int points, double angle){
super(x, y, points);
midX = x;
midY = y;
this.angle= angle;
}
public void right(){
angle += 5;
}
public void left(){
angle -= 5;
}
public void move(){
for (int i = 0; i < super.ypoints.length; i++){
super.ypoints[i] -= currSpeed;
//System.out.println(super.ypoints[i]);
//System.out.println(super.xpoints[i]);
}
//System.out.println(Arrays.toString(super.ypoints));
}
public double getSpeed(){
return currSpeed;
}
public void reverse(){
if (currSpeed > -15) currSpeed -= 0.2;
}
public void go(){
if (currSpeed < 25) currSpeed += 0.5;
}
public int getCenterX(){
return super.xpoints[2];
}
public int getCenterY(){
return super.ypoints[2];
}
public double getAng(){
return angle;
}
public void test(){
for (int x = 0; x < super.ypoints.length; x++){
super.ypoints[x] += 1000;
}
}
/*
public void decrement(){
if(currSpeed == 0){}
else if (currSpeed > 0 && currSpeed < 15){
currSpeed -= 0.05;
}
else if (currSpeed < 0 && currSpeed > -15){
currSpeed += 0.05;
}
System.out.println("losing speed");
}
*/
}
Laser Class (I don't think this is relevant either, but here ya go.)
package asteroidGame;
import java.awt.Color;
import java.awt.Rectangle;
import java.awt.geom.Rectangle2D;
public class Laser extends Rectangle{
private double angle;
public Laser(int x, int y , int width, int height, double ang){
super(x, y, width, height);
angle = ang;
Rectangle tst = new Rectangle();
}
public void move(){
super.y -= 35;
}
public double getAng(){
return angle;
}
public boolean intersects (Rectangle2D r){
//if intersects
if (super.intersects(r)){
return true;
}
else{
return false;
}
}
}
I was thinking of maybe turning the the Shape object transformed back into a Polygon to get the point, but I'm not sure how or if that would work.
You can use AffineTransform.transform(Point2D, Point2D) to transform a single point on your polygon.
Things would be a lot simpler for you if instead of trying to move the ship by using a rotation transform you kept a single (x,y) location of where the ship is. You'd move the ship's location in move() instead of trying to translate the polygon. Then when you want to paint the ship you e.g. do:
// Optionally copying the Graphics so the
// transform doesn't affect later painting.
Graphics2D temp = (Graphics2D) g2d.create();
temp.translate(ship.locX, ship.locY);
temp.rotate(ship.angle);
temp.draw(ship);
To move a point based on speed you can do this to find the movement vector:
double velX = speed * Math.cos(angle);
double velY = speed * Math.sin(angle);
locX += timeElapsed * velX;
locY += timeElapsed * velY;
That is essentially a conversion from polar to Cartesian coordinates. The x and y velocities are the legs of a triangle whose hypotenuse is speed and whose known angle is angle:
/|
/ |
/ |
/ |
speed / |
/ |
/ |velY
/ angle |
/)_______|
velX
There's an example of doing movement this way in an answer of mine here: https://stackoverflow.com/a/43692434/2891664.
For your comments:
Are you saying that, unlike my initial move function, just to make ship hold a single point, and thus I would only translate that instead?
More or less, yes. You'd still have a polygon to hold the ship's shape, but the points on the polygon would be relative to (0,0).
Suppose the following definitions:
Each (x,y) point on the polygon is pi. (In other words, one of p0, p1, p2 and p3.)
The (x,y) coordinates of the translation are T
Then, after translating the Graphics2D, each pi coordinate becomes pi+T on the panel. So if your polygon points are defined relative to (0,0) then translating to the ship's (locX,locY) will move the polygon to a location relative to (locX,locY).
It could be simplest then to define the point which is the tip of the polygon as being (0,0) so that after the translation the tip of the ship is the ship's location:
// Your original points:
int xPoints[] = {800, 780, 800, 820};
int yPoints[] = {400, 460, 440, 460};
// Become these points relative to (0,0):
int xPoints[] = {0, -20, 0, 20};
int yPoints[] = {0, 60, 40, 60};
And to e.g. start the ship in the same place, you would initialize its location to (800,400).
I was thinking about this again and realized the rotation is a little more complicated, because you probably don't want to rotate the ship around the tip. You probably want to rotate the ship around its center.
So, here's an MCVE demonstrating how to do all of this.
package mcve.game;
import javax.swing.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.awt.Polygon;
import java.awt.RenderingHints;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Rectangle;
import java.awt.Insets;
import java.awt.Toolkit;
import java.awt.GraphicsConfiguration;
import java.util.Set;
import java.util.HashSet;
import java.util.List;
import java.util.ArrayList;
public class MovementExample implements ActionListener {
public static void main(String[] args) {
SwingUtilities.invokeLater(MovementExample::new);
}
final int fps = 60;
final int period = 1000 / fps;
final JFrame frame;
final GamePanel panel;
final Controls controls;
final Ship ship;
final List<Bullet> bullets = new ArrayList<>();
MovementExample() {
frame = new JFrame("Movement Example");
Dimension size = getMaximumWindowSize(frame);
size.width /= 2;
size.height /= 2;
frame.setPreferredSize(size);
panel = new GamePanel();
frame.setContentPane(panel);
frame.pack();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
controls = new Controls();
ship = new Ship(panel.getWidth() / 2,
panel.getHeight() / 2);
new Timer(period, this).start();
}
#Override
public void actionPerformed(ActionEvent e) {
double secondsElapsed = 1.0 / fps;
ship.update(secondsElapsed);
bullets.forEach(b -> b.update(secondsElapsed));
Rectangle bounds = panel.getBounds();
bullets.removeIf(b -> !bounds.contains(b.locX, b.locY));
panel.repaint();
}
class GamePanel extends JPanel {
GamePanel() {
setBackground(Color.WHITE);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g.create();
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
if (ship != null) {
ship.draw(g2);
}
bullets.forEach(b -> b.draw(g2));
g2.dispose();
}
}
abstract class AbstractGameObject {
double maxSpeed;
double rotationAngle;
double locX;
double locY;
double velX;
double velY;
AbstractGameObject(double initialX, double initialY) {
locX = initialX;
locY = initialY;
}
abstract void update(double secondsElapsed);
abstract void draw(Graphics2D g2);
}
class Ship extends AbstractGameObject {
Polygon shape;
double rotationRate;
Ship(double initialX, double initialY) {
super(initialX, initialY);
maxSpeed = 128; // pixels/second
rotationAngle = Math.PI * 3 / 2;
rotationRate = (2 * Math.PI) / 2; // radians/second
int xPoints[] = {0, -20, 0, 20};
int yPoints[] = {0, 60, 40, 60};
shape = new Polygon(xPoints, yPoints, 4);
}
Point2D.Double getTip() {
Point2D.Double center = getCenter();
// The tip is at (0,0) and it's already centered
// on the x-axis origin, so the distance from the
// tip to the center is just center.y.
double distance = center.y;
// Then find the location of the tip, relative
// to the center.
double tipX = distance * Math.cos(rotationAngle);
double tipY = distance * Math.sin(rotationAngle);
// Now find the actual location of the center.
center.x += locX;
center.y += locY;
// And return the actual location of the tip, relative
// to the actual location of the center.
return new Point2D.Double(tipX + center.x, tipY + center.y);
}
Point2D.Double getCenter() {
// Returns the center point of the ship,
// relative to (0,0).
Point2D.Double center = new Point2D.Double();
for (int i = 0; i < shape.npoints; ++i) {
center.x += shape.xpoints[i];
center.y += shape.ypoints[i];
}
center.x /= shape.npoints;
center.y /= shape.npoints;
return center;
}
#Override
void update(double secondsElapsed) {
// See my answer here: https://stackoverflow.com/a/43692434/2891664
// for a discussion of why this logic is the way it is.
double speed = 0;
if (controls.isUpHeld()) {
speed += maxSpeed;
}
if (controls.isDownHeld()) {
speed -= maxSpeed;
}
velX = speed * Math.cos(rotationAngle);
velY = speed * Math.sin(rotationAngle);
locX += secondsElapsed * velX;
locY += secondsElapsed * velY;
double rotation = 0;
if (controls.isLeftHeld()) {
rotation -= rotationRate;
}
if (controls.isRightHeld()) {
rotation += rotationRate;
}
rotationAngle += secondsElapsed * rotation;
// Cap the angle so it can never e.g. get so
// large that it loses precision.
if (rotationAngle > 2 * Math.PI) {
rotationAngle -= 2 * Math.PI;
}
if (controls.isFireHeld()) {
Point2D.Double tipLoc = getTip();
Bullet bullet = new Bullet(tipLoc.x, tipLoc.y, rotationAngle);
bullets.add(bullet);
}
}
#Override
void draw(Graphics2D g2) {
Graphics2D copy = (Graphics2D) g2.create();
copy.setColor(Color.RED);
// Translate to the ship's location.
copy.translate(locX, locY);
// Rotate the ship around its center.
Point2D.Double center = getCenter();
// The PI/2 offset is necessary because the
// polygon points are defined with the ship
// already vertical, i.e. at an angle of -PI/2.
copy.rotate(rotationAngle + (Math.PI / 2), center.x, center.y);
copy.fill(shape);
}
}
class Bullet extends AbstractGameObject {
Ellipse2D.Double shape = new Ellipse2D.Double();
Bullet(double initialX, double initialY, double initialRotation) {
super(initialX, initialY);
maxSpeed = 512;
rotationAngle = initialRotation;
velX = maxSpeed * Math.cos(rotationAngle);
velY = maxSpeed * Math.sin(rotationAngle);
double radius = 3;
shape.setFrame(-radius, -radius, 2 * radius, 2 * radius);
}
#Override
void update(double secondsElapsed) {
locX += secondsElapsed * velX;
locY += secondsElapsed * velY;
}
#Override
void draw(Graphics2D g2) {
Graphics2D copy = (Graphics2D) g2.create();
copy.setColor(Color.BLACK);
copy.translate(locX, locY);
copy.fill(shape);
}
}
// See https://docs.oracle.com/javase/tutorial/uiswing/misc/keybinding.html
class Controls {
final Set<Integer> keysHeld = new HashSet<>();
Controls() {
bind(KeyEvent.VK_A, "left");
bind(KeyEvent.VK_D, "right");
bind(KeyEvent.VK_W, "up");
bind(KeyEvent.VK_S, "down");
bind(KeyEvent.VK_SPACE, "fire");
}
boolean isLeftHeld() { return keysHeld.contains(KeyEvent.VK_A); }
boolean isRightHeld() { return keysHeld.contains(KeyEvent.VK_D); }
boolean isUpHeld() { return keysHeld.contains(KeyEvent.VK_W); }
boolean isDownHeld() { return keysHeld.contains(KeyEvent.VK_S); }
boolean isFireHeld() { return keysHeld.contains(KeyEvent.VK_SPACE); }
void bind(int keyCode, String name) {
bind(keyCode, name, true);
bind(keyCode, name, false);
}
void bind(int keyCode, String name, boolean isOnRelease) {
KeyStroke stroke = KeyStroke.getKeyStroke(keyCode, 0, isOnRelease);
name += isOnRelease ? ".released" : ".pressed";
panel.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW)
.put(stroke, name);
panel.getActionMap()
.put(name, new AbstractAction() {
#Override
public void actionPerformed(ActionEvent e) {
if (isOnRelease) {
keysHeld.remove(keyCode);
} else {
keysHeld.add(keyCode);
}
}
});
}
}
// This returns the usable size of the display which
// the JFrame resides in, as described here:
// http://docs.oracle.com/javase/8/docs/api/java/awt/GraphicsEnvironment.html#getMaximumWindowBounds--
static Dimension getMaximumWindowSize(JFrame frame) {
GraphicsConfiguration config = frame.getGraphicsConfiguration();
Dimension size = config.getBounds().getSize();
Insets insets = Toolkit.getDefaultToolkit().getScreenInsets(config);
size.width -= insets.left + insets.right;
size.height -= insets.top + insets.bottom;
return size;
}
}
There are other ways the tip of the ship could be calculated, but the way I did it in the MCVE is this:
Get the center point of the ship, relative to (0,0).
Get the distance from the center point to the tip. The tip is at (0,0) so this is just the y-coordinate of the center.
Then calculate the (x,y) location of the tip, relative to the center. This is done in a very similar way to the figure above for speed and velocity, but the hypotenuse is the distance between the center and the tip of the ship.
Translate the center to be relative to the ship's location.
Translate the location of the tip (which is relative to the center) to be relative to the ship's location.
It could also all be done with an AffineTransform, similar to what you are doing in the code in the question, but you'd set it on every update. Something like this:
AffineTransform transform = new AffineTransform();
#Override
void update(double secondsElapsed) {
...
// Clear the previous translation and rotation.
transform.setToIdentity();
// Set to current.
transform.translate(locX, locY);
Point2D.Double center = getCenter();
transform.rotate(rotationAngle + (Math.PI / 2), center.x, center.y);
if (controls.isFireHeld()) {
Point2D.Double tip = new Point2D.Double(0, 0);
transform.transform(tip, tip);
Bullet bullet = new Bullet(tip.x, tip.y, rotationAngle);
bullets.add(bullet);
}
}
You could still use a transform to do calculations that way, but you don't end up with any strangeness from depending on the transform for movement. (In the code in the question, the ship is e.g. only ever moved along the y-axis. The apparent sideways movement is due to the series of rotation concatenations.)
I'm trying to create a Roomba program with a ball that bounces around the screen that cleans the tiles that it passes over. The program should start with all grey tiles and when the ball passes over them then the tiles turn white. Currently I have the ball that bounces around everywhere and a grid method which creates a 5x5 grid.
I have encountered two problems:
I cannot make the grid and the ball appear in the same simulation while running the program, it's either one or the other.
I'm having trouble with finding a way to analyze if the ball has passed over certain squares in the grid, perhaps I need to create an object for the grid/ball?
My code:
import edu.princeton.cs.introcs.StdDraw;
public class Roomba {
private static int windowWidth = 200;
private static int windowHeight = 200;
private static double x = 100;
private static double y = 100;
private static double vx = 2;
private static double vy = 4;
private static int radius = 5;
private static boolean inGame = true;
public static void updateLocations() {
x += vx;
y += vy;
}
public static void drawGrid() {
StdDraw.setScale(0, 5);
int[][] grid = new int[5][5];
for (int x = 0; x < grid.length; x++) {
for (int y = 0; y < grid.length; y++) {
grid[x][y] = 255;
}
}
for (int x = 0; x < grid.length; x++) {
for (int y = 0; y < grid.length; y++) {
StdDraw.square(x, y, 1);
}
}
}
public static void updateVelocities() {
if (y + radius >= windowHeight) {
vy = -vy;
} else if (y - radius <= 0) {
vy = -vy;
}
if (x >= 194 || x <= 6) {
vx = -vx;
}
}
public static void setBackground() {
StdDraw.clear(StdDraw.GRAY);
// drawGrid();
}
public static void drawBall() {
StdDraw.setPenColor(StdDraw.BLACK);
StdDraw.filledCircle(x, y, radius);
// StdDraw.setPenColor(StdDraw.RED);
// StdDraw.filledSquare(x + 3, y + 3, 1);
StdDraw.setPenColor(StdDraw.BLACK);
StdDraw.text(100, 70, "x is: " + x + " y is: " + y);
}
public static void draw() {
setBackground();
drawBall();
}
public static void main(String[] args) {
StdDraw.setCanvasSize(800, 800);
StdDraw.setXscale(0, windowWidth);
StdDraw.setYscale(0, windowHeight);
while (true) {
if (inGame) {
draw();
updateVelocities();
updateLocations();
} else {
StdDraw.text(100, 100, "Game Over");
}
// change to if all tiles have been cleaned
// if (x + radius > windowWidth || x - radius < 0) {
// inGame = false;
// }
StdDraw.show(20);
}
}
}
Maybe the background is being drawn over the ball or vice verse? Try to draw the ball first then the background? Make sure the ball is actually being rendered at the correct size and not as the entire screen. I'm not to familiar with 2D graphics but maybe there is some z fighting?
private void addBricks(){
for (int i = 0; i < NBRICK_ROWS; i++){
for (int j = 0; j < NBRICKS_PER_ROW; j++){
int y = BRICK_Y_OFFSET + (i * (BRICK_HEIGHT + BRICK_SEP));
int x = (BRICK_X_OFFSET) + (j * (BRICK_WIDTH + BRICK_SEP));
brick = new GRect (x, y, BRICK_WIDTH, BRICK_HEIGHT );
add (brick);
}
}
}
I am trying to make a breakout game here and this is a snippet of code.
I have added a set of rectangles to my canvas. Later in my program I would like to remove some of them when the ball hits them. The problem is that I do not know how to refer to them specifically. That is to say that I do not know what parameters to input in remove() since all of them were created as brick
Thanks!
Whole program below
import acm.graphics.*;
import acm.program.*;
import acm.util.*;
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
public class Breakout extends GraphicsProgram {
/** Width and height of application window in pixels */
public static final int APPLICATION_WIDTH = 440;
public static final int APPLICATION_HEIGHT = 660;
/** Dimensions of game board (usually the same) */
private static final int WIDTH = 400;
private static final int HEIGHT = 600;
/** Dimensions of the paddle */
private static final int PADDLE_WIDTH = 60;
private static final int PADDLE_HEIGHT = 10;
/** Offset of the paddle up from the bottom */
private static final int PADDLE_Y_OFFSET = 30;
/** Number of bricks per row */
private static final int NBRICKS_PER_ROW = 10;
/** Number of rows of bricks */
private static final int NBRICK_ROWS = 10;
/** Separation between bricks */
private static final int BRICK_SEP = 4;
/** Width of a brick */
private static final int BRICK_WIDTH =
(WIDTH - (NBRICKS_PER_ROW - 1) * BRICK_SEP) / NBRICKS_PER_ROW;
/** Height of a brick */
private static final int BRICK_HEIGHT = 8;
/** Radius of the ball in pixels */
private static final int BALL_RADIUS = 10;
/** Offset of the top brick row from the top */
private static final int BRICK_Y_OFFSET = 70;
/** Offset of the side bricks from the sides of game window so that the whole set of bricks are in the centre */
private static final int BRICK_X_OFFSET = ((WIDTH - NBRICKS_PER_ROW * (BRICK_WIDTH + BRICK_SEP) + BRICK_SEP) / 2);
/** Number of turns */
private static final int NTURNS = 3;
/** Game speed */
private static final int DELAY = 1;
/* Method: run() */
/** Runs the Breakout program. */
public void run() {
addMouseListeners();
addWorld();
runGame();
}
private void addWorld(){
setSize (APPLICATION_WIDTH, APPLICATION_HEIGHT);
addPlayingBox();
addBricks();
addPaddle();
}
/* lives and number of bricks will be check before game runs
* if there are either no lives of bricks left game is over
* ball and ball physics are only added to the screen after there is a mouse click.
*/
private void runGame(){
while (true){
// add a gameover label
waitForClick();
addBall();
addBallMotion();
}
}
//adds the playing area onto screen
private void addPlayingBox(){
topBounds = new GLine (0, 0, WIDTH, 0);
bottomBounds = new GLine (0, HEIGHT, WIDTH, HEIGHT);
leftBounds = new GLine (0, 0, 0, HEIGHT);
rightBounds = new GLine (WIDTH, 0, WIDTH, HEIGHT);
add (topBounds);
add (bottomBounds);
add (leftBounds);
add (rightBounds);
}
/*bricks are added to the top row and left column 1st and consequently to the its right column
* and to the next row when a row is all filled up
*/
private void addBricks(){
for (int i = 0; i < NBRICK_ROWS; i++){
for (int j = 0; j < NBRICKS_PER_ROW; j++){
int y = BRICK_Y_OFFSET + (i * (BRICK_HEIGHT + BRICK_SEP));
int x = (BRICK_X_OFFSET) + (j * (BRICK_WIDTH + BRICK_SEP));
brick = new GRect (x, y, BRICK_WIDTH, BRICK_HEIGHT );
colorBrick(brick, i);
add (brick);
}
}
}
// every consecutive 2 rows are colored the same
private void colorBrick(GRect brick, int rowNumber){
brick.setFilled (true);
switch (rowNumber + 1) {
case 1: case 2: brick.setColor(Color.red);
break;
case 3: case 4: brick.setColor(Color.orange);
break;
case 5: case 6: brick.setColor(Color.yellow);
break;
case 7: case 8: brick.setColor(Color.green);
break;
case 9: case 10:brick.setColor(Color.cyan);
break;
}
}
//adds paddle to screen
private void addPaddle(){
paddle = new GRect (WIDTH / 2 - PADDLE_WIDTH / 2, HEIGHT - PADDLE_Y_OFFSET, PADDLE_WIDTH, PADDLE_HEIGHT);
paddle.setFilled(true);
paddle.setColor (Color.BLACK);
add (paddle);
}
//creates motion for the paddle according to mouse movement
public void mouseMoved(MouseEvent e){
paddle.setLocation ((e.getX() - PADDLE_WIDTH / 2), (double) (HEIGHT - PADDLE_Y_OFFSET));
/* checks if the paddle within the playing area
* if not, the paddles will stay at the extremities*/
if ( paddle.getX() > (WIDTH - PADDLE_WIDTH)){
paddle.setLocation((double) (WIDTH - PADDLE_WIDTH), (double) (HEIGHT - PADDLE_Y_OFFSET));
}
if ( paddle.getX() < 0){
paddle.setLocation((double) 0, (double) (HEIGHT - PADDLE_Y_OFFSET));
}
}
/* creates the ball
*/
private void addBall(){
double ballInitXPosition = WIDTH / 2 - BALL_RADIUS;
double ballInitYPosition = HEIGHT / 2 - BALL_RADIUS;
ball = new GOval (ballInitXPosition, ballInitYPosition,
BALL_RADIUS * 2, BALL_RADIUS * 2);
ball.setFilled(true);
ball.setColor(Color.BLACK);
add (ball);
}
/* kick start the ball motion with predetermined values
*/
private void addBallMotion(){
// y component of starting velocity; pixels per second
vy = 0.3;
/* x component of starting velocity; pixels per second
* which ranges according to the random generator
* can be negative or positive, ball can go left or right with equal chances
* angle must not be 0 or 180 degrees otherwise the ball will not move anywhere else
*/
vx = rgen.nextDouble(0.0, 0.5);
if (rgen.nextBoolean(0.5)){
vx = -vx;
}
while (true){
ball.move(vx, vy);
checkCollision();
pause(DELAY);
}
}
private void checkCollision(){
checkWallCollision();
checkBrickAndPaddleCollision();
}
//checks for wall collision
private void checkWallCollision(){
if ( (getCollidingObject() == leftBounds) || (getCollidingObject() == rightBounds )){
vx = -vx;
}
//checks for floor and ceiling collision collision
if ( (getCollidingObject() == topBounds) ){
vy = -vy;
}
if ( (getCollidingObject() == bottomBounds)){
remove (ball);
runGame();
}
}
/* check if there is any collision with brick or paddle
*/
private void checkBrickAndPaddleCollision(){
GObject collider = getCollidingObject();
/* brick is removed and y direction of ball is reversed
* bricks counter goes down by 1 and score goes up by 1
*/
if (collider != paddle &&
collider != null &&
collider != topBounds &&
collider != rightBounds &&
collider != bottomBounds &&
collider != leftBounds){
remove(collider);
vy = -vy;
}
/* collide with paddle, y direction is reversed
*/
else if (collider == paddle){
vy = -vy;
}
}
//check for collision at the 4 sides of the ball
//starting with the top and going clockwise
//returns the object nearest to the screen that touches the sides of the ball
private GObject getCollidingObject(){
GObject ballTop = getElementAt ( (ball.getX() + BALL_RADIUS), (ball.getY() - .1) );
GObject ballRight = getElementAt ( (ball.getX() + (BALL_RADIUS * 2) + .1), (ball.getY() + BALL_RADIUS) );
GObject ballBottom = getElementAt ( (ball.getX() + BALL_RADIUS), ball.getY() + (BALL_RADIUS * 2) + .1);
GObject ballLeft= getElementAt ( (ball.getX() - .1), (ball.getY() + BALL_RADIUS) );
if (ballTop != null){
return (ballTop);
}
else if (ballRight != null){
return (ballRight);
}
else if (ballBottom != null){
return (ballBottom);
}
else if (ballLeft != null){
return (ballLeft);
}
return (null);
}
private GRect paddle; // creates a paddle that only moves linearly according to mouses' x coordinate
private GRect brick;
private GOval ball;
private double vx, vy; // x and y components of the ball's velocity
private RandomGenerator rgen = RandomGenerator.getInstance();
// creates a bounding box that is the playing area
private GLine topBounds;
private GLine bottomBounds;
private GLine leftBounds;
private GLine rightBounds;
}
You'll have to maintain a separate mapping of which bricks exist. I imagine you'd need something like this to do collision detection as well. I would do something like the following.
public class Game
{
Collection<Brick> bricks;
Ball ball;
public void initLocation()
{
for (int i = 0; i < NBRICK_ROWS; i++)
{
for (int j = 0; j < NBRICKS_PER_ROW; j++)
{
int y = BRICK_Y_OFFSET + (i * (BRICK_HEIGHT + BRICK_SEP));
int x = (BRICK_X_OFFSET) + (j * (BRICK_WIDTH + BRICK_SEP));
bricks.add(new Brick(x, y));
}
}
}
public void drawBricks()
{
for (Brick brick : bricks)
{
brickRect = new GRect(x, y, BRICK_WIDTH, BRICK_HEIGHT);
add(brick);
}
}
}
public class Brick
{
int x;
int y;
public Brick(int x, int y)
{
this.x = x;
this.y = y;
}
}
public class Ball
{
int x;
int y;
}
This code isn't complete but should give you an idea on how to keep a reference to the brick. When you're checking for collision, you can iterate through the bricks, find any the have a collision with the ball and then call remove() on that brick.
So, if you are using add() from an external library (acm.graphics), you'll need to keep your own copies of bricks that you add. Perhaps add a 2D array of boolean values or a structure like #thattolleyguy suggested to your class then a method to add them
private void addBrick(int x, int y)
{
brickArray[x][y] = true; //your own copy of brick locations
int yloc = BRICK_Y_OFFSET + (i * (BRICK_HEIGHT + BRICK_SEP));
int xloc = (BRICK_X_OFFSET) + (j * (BRICK_WIDTH + BRICK_SEP));
brick = new GRect (xloc, yloc, BRICK_WIDTH, BRICK_HEIGHT );
add (brick);
}
Then you can easily remove them from your array (set that location to false) and from your external library (or you may need a redraw) with a removeBrick method.
Also
The object reference brick is only referenced within this function so it only needs to be local
private void addBricks()
{
GRect brick;
...
add(brick);
...
}
If I was you, I would store all GRects in a List<GRect>. This list should be at the center of your operations.
I suppose the drawing are triggered by repaint() method. Possibly in a sperate thread, you need to check the distance between the ball and each GRect, when you find a GRect intersected with the ball, you can pass that GRect to remove().
One simple solution is to keep an isVisible flag in each GRect and modify it in remove(). BTW, Java Objects are passed by reference, your modification will take effects.
I am new to Java and am learning from Stanford lectures from YouTube.
So I was trying out their assignment to make a breakout game and so far so good until now. I have all my bricks, ball and paddle including the mechanics of the game but when i run the game only one brick can be removed when hit by the ball. see this. That brick happens to be the last brick added to the canvas.
The ball just flies past all other bricks with no effect. The relevant code is below.
Am I lacking some important knowledge about getElementAt here? I have a feeling that getCollidingObject is not assigned to collider, which is making the collision detection faulty. I hope someone can enlighten me on this!
private void addBallMotion(){
// y component of starting velocity; pixels per second
vy = 3.0;
/* x component of starting velocity; pixels per second
* which ranges according to the random generator
* can be negative or positive, ball can go left or right with equal chances
*/
vx = rgen.nextDouble(1.0, 3.0);
if (rgen.nextBoolean(0.5)){
vx = -vx;
}
while (true){
ball.move(vx, vy);
checkCollision();
pause(FPS);
}
}
private void checkCollision(){
checkWallCollision();
checkBrickAndPaddleCollision();
}
private void checkWallCollision(){
//checks for left or right collision
if ( (ball.getX() < leftBounds.getX() ) || (ball.getX() + BALL_RADIUS * 2 > rightBounds.getX()) ){
vx = -vx;
}
//checks for top or bottom collision
if ( (ball.getY() < topBounds.getY() ) || (ball.getY() + BALL_RADIUS * 2 > bottomBounds.getY()) ){
vy = -vy;
}
}
private void checkBrickAndPaddleCollision(){
GObject collider = getCollidingObject();
if (collider == brick){
remove(collider);
vy = -vy;
}
if (collider == paddle){
vy = -vy;
}
}
//check for collision at the 4 edges of the ball
//starting with the left and going clockwise
private GObject getCollidingObject(){
GObject ballLeft= getElementAt (ball.getX() - 1, ball.getY() + BALL_RADIUS);
GObject ballRight= getElementAt (ball.getX() + BALL_RADIUS * 2 + 1, ball.getY() + BALL_RADIUS);
GObject ballTop = getElementAt (ball.getX() + BALL_RADIUS * 2, ball.getY() - 1);
GObject ballBottom= getElementAt (ball.getX() + BALL_RADIUS, ball.getY() + BALL_RADIUS * 2 + 1);
if (ballLeft != null){
return (ballLeft);
}
else if (ballTop != null){
return (ballTop);
}
else if (ballRight != null){
return (ballRight);
}
else if (ballBottom != null){
return (ballBottom);
}
return (null);
}
private GRect paddle; // creates a paddle that only moves linearly according to mouses' x coordinate
private GRect brick;
private GOval ball;
private double vx, vy; // x and y components of the ball's velocity
//private GObject collider;
Here's the whole program:
import acm.graphics.*;
import acm.program.*;
import acm.util.*;
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
public class Breakout extends GraphicsProgram {
/** Width and height of application window in pixels */
public static final int APPLICATION_WIDTH = 400;
public static final int APPLICATION_HEIGHT = 600;
/** Dimensions of game board (usually the same) */
private static final int WIDTH = APPLICATION_WIDTH;
private static final int HEIGHT = APPLICATION_HEIGHT;
/** Dimensions of the paddle */
private static final int PADDLE_WIDTH = 60;
private static final int PADDLE_HEIGHT = 10;
/** Offset of the paddle up from the bottom */
private static final int PADDLE_Y_OFFSET = 30;
/** Number of bricks per row */
private static final int NBRICKS_PER_ROW = 10;
/** Number of rows of bricks */
private static final int NBRICK_ROWS = 10;
/** Separation between bricks */
private static final int BRICK_SEP = 4;
/** Width of a brick */
private static final int BRICK_WIDTH =
(WIDTH - (NBRICKS_PER_ROW - 1) * BRICK_SEP) / NBRICKS_PER_ROW;
/** Height of a brick */
private static final int BRICK_HEIGHT = 8;
/** Radius of the ball in pixels */
private static final int BALL_RADIUS = 10;
/** Offset of the top brick row from the top */
private static final int BRICK_Y_OFFSET = 70;
/** Offset of the side bricks from the sides of game window */
private static final int BRICK_X_OFFSET = ((WIDTH - NBRICKS_PER_ROW * (BRICK_WIDTH + BRICK_SEP) + BRICK_SEP) / 2);
/** Number of turns */
private static final int NTURNS = 3;
/** Number of frames per second */
private static final int FPS = 1;
/* Method: run() */
/** Runs the Breakout program. */
public void run() {
addMouseListeners();
addWorld();
// runGame();
}
private void addWorld(){
setSize (APPLICATION_WIDTH, APPLICATION_HEIGHT);
addPlayingBox();
addBricks();
addPaddle();
addBall();
// addCounter();
}
//adds the bound area onto screen
private void addPlayingBox(){
topBounds = new GLine (0, 0, WIDTH, 0);
bottomBounds = new GLine (0, HEIGHT, WIDTH, HEIGHT);
leftBounds = new GLine (0, 0, 0, HEIGHT);
rightBounds = new GLine (WIDTH, 0, WIDTH, HEIGHT);
add (topBounds);
add (bottomBounds);
add (leftBounds);
add (rightBounds);
}
private void addBricks(){
for (int i = 0; i < NBRICK_ROWS; i++){
int y = BRICK_Y_OFFSET + (i * (BRICK_HEIGHT + BRICK_SEP));
for (int j = 0; j < NBRICKS_PER_ROW; j++){
int x = (BRICK_X_OFFSET) + (j * (BRICK_WIDTH + BRICK_SEP));
brick = new GRect (x, y, BRICK_WIDTH, BRICK_HEIGHT );
colorBrick(brick, i);
add (brick);
}
}
}
// every consecutive 2 rows are colored the same
private void colorBrick(GRect brick, int rowNumber){
brick.setFilled (true);
switch (rowNumber + 1) {
case 1: case 2: brick.setColor(Color.red);
break;
case 3: case 4: brick.setColor(Color.orange);
break;
case 5: case 6: brick.setColor(Color.yellow);
break;
case 7: case 8: brick.setColor(Color.green);
break;
case 9: case 10:brick.setColor(Color.cyan);
break;
}
}
//adds paddle to screen
private void addPaddle(){
paddle = new GRect (PADDLE_WIDTH, PADDLE_HEIGHT);
paddle.setFilled(true);
paddle.setColor (Color.BLACK);
add (paddle);
}
//creates motion for the paddle according to mouse movement
public void mouseMoved(MouseEvent e){
paddle.setLocation ((e.getX() - PADDLE_WIDTH / 2), (double) (HEIGHT - PADDLE_Y_OFFSET));
/* checks if the paddle within the playing area
* if not the paddles will stay at the extremities*/
if ( paddle.getX() > (WIDTH - PADDLE_WIDTH)){
paddle.setLocation((double) (WIDTH - PADDLE_WIDTH), (double) (HEIGHT - PADDLE_Y_OFFSET));
}
if ( paddle.getX() < 0){
paddle.setLocation((double) 0, (double) (APPLICATION_HEIGHT - PADDLE_Y_OFFSET));
}
}
private void addBall(){
ball = new GOval (((WIDTH - BALL_RADIUS * 2) / 2), ((HEIGHT - BALL_RADIUS * 2) / 2),
BALL_RADIUS * 2, BALL_RADIUS * 2);
ball.setFilled(true);
ball.setColor(Color.BLACK);
add (ball);
addBallMotion();
}
private void addBallMotion(){
// y component of starting velocity; pixels per second
vy = 3.0;
/* x component of starting velocity; pixels per second
* which ranges according to the random generator
* can be negative or positive, ball can go left or right with equal chances
*/
vx = rgen.nextDouble(1.0, 3.0);
if (rgen.nextBoolean(0.5)){
vx = -vx;
}
while (true){
ball.move(vx, vy);
checkCollision();
pause(FPS);
}
}
private void checkCollision(){
checkWallCollision();
checkBrickAndPaddleCollision();
}
private void checkWallCollision(){
//checks for left or right collision
if ( (ball.getX() < leftBounds.getX() ) || (ball.getX() + BALL_RADIUS * 2 > rightBounds.getX()) ){
vx = -vx;
}
//checks for top or bottom collision
if ( (ball.getY() < topBounds.getY() ) || (ball.getY() + BALL_RADIUS * 2 > bottomBounds.getY()) ){
vy = -vy;
}
}
private void checkBrickAndPaddleCollision(){
GObject collider = getCollidingObject();
if (collider == brick){
remove(collider);
vy = -vy;
}
if (collider == paddle){
vy = -vy;
}
}
//check for collision at the 4 edges of the ball
//starting with the left and going clockwise
private GObject getCollidingObject(){
GObject ballLeft= getElementAt (ball.getX() - 1, ball.getY() + BALL_RADIUS);
GObject ballRight= getElementAt (ball.getX() + BALL_RADIUS * 2 + 1, ball.getY() + BALL_RADIUS);
GObject ballTop = getElementAt (ball.getX() + BALL_RADIUS * 2, ball.getY() - 1);
GObject ballBottom= getElementAt (ball.getX() + BALL_RADIUS, ball.getY() + BALL_RADIUS * 2 + 1);
if (ballLeft != null){
return (ballLeft);
}
else if (ballTop != null){
return (ballTop);
}
else if (ballRight != null){
return (ballRight);
}
else if (ballBottom != null){
return (ballBottom);
}
return (null);
}
private GRect paddle; // creates a paddle that only moves linearly according to mouses' x coordinate
private GRect brick;
private GOval ball;
private double vx, vy; // x and y components of the ball's velocity
private RandomGenerator rgen = RandomGenerator.getInstance();
//private GObject collider;
private GLine topBounds; // creates a bounding box that is the playing area
private GLine bottomBounds;
private GLine leftBounds;
private GLine rightBounds;
}
Exactly as I thought.
Look - You have a field in your class called brick. It's of GRect type. At the beginning you're calling addWorld() method, which calls addBricks(). Now check what you wrote:
private void addBricks(){
for (int i = 0; i < NBRICK_ROWS; i++){
int y = BRICK_Y_OFFSET + (i * (BRICK_HEIGHT + BRICK_SEP));
for (int j = 0; j < NBRICKS_PER_ROW; j++){
int x = (BRICK_X_OFFSET) + (j * (BRICK_WIDTH + BRICK_SEP));
brick = new GRect (x, y, BRICK_WIDTH, BRICK_HEIGHT );
colorBrick(brick, i);
add (brick);
}
}
}
What happens in there? You're having a loop in which brick is overriden NBRICK_ROWS * NBRICKS_PER_ROW times, which causes brick field to be the last created brick on your screen.
Basically, you're doing something similar to this:
int x;
x = 5;
x = 6;
x = 8;
// x is 8 now
And in checkBrickAndPaddleCollision() you're checking only if collider is brick. Which in other words means, you're checking if it's the last brick - if it is, then you remove it.
First of all you should create an array of bricks, not just one field.
ArrayList<GRect> bricks;
instead of:
GRect brick;
And then in addBricks() method, you should have:
bricks.add(new GRect (x, y, BRICK_WIDTH, BRICK_HEIGHT));
instead of:
brick = new GRect (x, y, BRICK_WIDTH, BRICK_HEIGHT );
After this, in checkBrickAndPaddleCollision(), you should not check:
if (collider == brick) {
remove(collider);
vy = -vy;
}
but rather all bricks:
for(GRect brick : bricks) {
if (collider.equals(brick)) { // Note that you should rather use .equals, instead of == as Aurand stated in his comment
remove(collider);
vy = -vy;
}
}
I'm trying to learn java by following the cs106a course online.
Currently I've arrived at the breakout exersize and I'm having some trouble with bugs
I haven't finished it completely but I want to solves these issues first before I go further.
Problem 1:
when the ball collides with the bricks they don't always seem to be removed from the canvas.
sometimes the brick will be removed on a second time it collides. But there is one row (of yellow bricks) that doesn't respond at all to the ball collisions.
Problem 2:
my paddle can be moved by dragging the mouse. the only problem is. the bricks can also be moved like the paddle.
I know it has something to do with this piece of code
gobj = getElementAt(lastX, lastY);
If I remove it altogether the bricks aren't moveable anymore. which is good. but I'm still
able to move the paddle no matter where I click and drag.
can anyone give me a hint so I can correct the mistakes?
Here's my code below.
Thanks
/*
* File: Breakout.java
* -------------------
* This file will eventually implement the game of Breakout.
*/
import acm.graphics.*;
import acm.program.*;
import acm.util.*;
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import org.omg.CORBA.PUBLIC_MEMBER;
public class breakout extends GraphicsProgram {
/** Width and height of application window in pixels */
public static final int APPLICATION_WIDTH = 400;
public static final int APPLICATION_HEIGHT = 600;
/** Dimensions of game board (usually the same) */
private static final int WIDTH = APPLICATION_WIDTH;
private static final int HEIGHT = APPLICATION_HEIGHT;
/** Dimensions of the paddle */
private static final int PADDLE_WIDTH = 60;
private static final int PADDLE_HEIGHT = 10;
/** Offset of the paddle up from the bottom */
private static final int PADDLE_Y_OFFSET = 30;
/** Number of bricks per row */
private static final int NBRICKS_PER_ROW = 10;
/** Number of rows of bricks */
private static final int NBRICK_ROWS = 8;
/** Separation between bricks */
private static final int BRICK_SEP = 4;
/** Width of a brick */
private static final int BRICK_WIDTH = (WIDTH - (NBRICKS_PER_ROW - 1)* BRICK_SEP)/ NBRICKS_PER_ROW;
/** Height of a brick */
private static final int BRICK_HEIGHT = 8;
/** Radius of the ball in pixels */
private static final int BALL_RADIUS = 10;
/** Offset of the top brick row from the top */
private static final int BRICK_Y_OFFSET = 70;
/** Number of turns */
private static final int NTURNS = 3;
private static final int DELAY = 50;
private static final double X_START = WIDTH / 2;
private static final double Y_START = 450;
public void run() {
world();
play();
}
private void ball() {
ball = new GOval(X_START, Y_START, BALL_RADIUS, BALL_RADIUS);
ball.setFillColor(Color.BLACK);
ball.setFilled(true);
add(ball);
}
private void paddle() {
paddle = new GRect(100, 500, PADDLE_WIDTH, PADDLE_HEIGHT);
paddle.setColor(Color.BLACK);
paddle.setFilled(true);
add(paddle);
}
private void brick(int x, int y, Color c) {
GRect brick = new GRect(x, y, BRICK_WIDTH, BRICK_HEIGHT);
brick.setColor(getBackground());
brick.setFillColor(c);
brick.setFilled(true);
add(brick);
}
private void brickRow(int x, int y, Color c) {
x = BRICK_SEP / 2;
y += BRICK_Y_OFFSET;
for (int i = 0; i < NBRICKS_PER_ROW; i++) {
brick(x, y, c);
x += BRICK_WIDTH + BRICK_SEP;
}
}
private void world() {
//initialize x and y position for the rows of bricks
int x = 0;
int y = 0;
// set starting color for first row
Color c = Color.red;
paddle();
//create 2 rows of bricks and switch colors
for (int i = 0; i < NBRICK_ROWS; i++) {
if (i <= 1) {
c = Color.ORANGE;
} else if (i > 1 && i <= 3) {
c = Color.YELLOW;
} else if (i > 3 && i <= 5) {
c = Color.GREEN;
} else if (i > 5 && i <= 7) {
c = Color.CYAN;
}
brickRow(x, y, c);
y += BRICK_HEIGHT + BRICK_SEP;
}
}
private void moveBall() {
ball.move(xVel, yVel);
}
public void mousePressed(MouseEvent e) {
lastX = e.getX();
lastY = e.getY();
gobj = getElementAt(lastX, lastY);
}
public void mouseDragged(MouseEvent e) {
if (paddle != null) {
paddle.move(e.getX() - lastX, getY());
lastX = e.getX();
lastY = e.getY();
}
//constrain paddle movement
if (paddle.getX() < 0){
paddle.setLocation(0, 500);
}else if (paddle.getX()+BRICK_WIDTH > WIDTH ){
paddle.setLocation(WIDTH-BRICK_WIDTH, 500);
}
}
private void checkForCollision() {
// ball collission with walls
if (ball.getY() > getHeight() - BALL_RADIUS
|| ball.getY() < 0 + BALL_RADIUS) {
yVel = -yVel;
} else if (ball.getX() > getWidth() - BALL_RADIUS
|| ball.getX() < 1 + BALL_RADIUS) {
xVel = -xVel;
// ball collission with paddle
} else if (getElementAt(ball.getX() + BALL_RADIUS, ball.getY()
+ BALL_RADIUS) == paddle) {
yVel = -yVel;
// check for collision with bricks to remove them but ignore collision with paddle
} else if (getElementAt(ball.getX(), ball.getY()) != null
&& getElementAt(ball.getX(), ball.getY()) != paddle) {
remove(getCollidingObject(ball.getX(), ball.getY()));
yVel = -yVel;
} else if (getElementAt(ball.getX() + BALL_RADIUS, ball.getY()
+ BALL_RADIUS) != null
&& getElementAt(ball.getX() + BALL_RADIUS, ball.getY()
+ BALL_RADIUS) != paddle) {
remove(getCollidingObject(ball.getX() + BALL_RADIUS, ball.getY()
+ BALL_RADIUS));
yVel = -yVel;
} else if (getElementAt(ball.getX() + BALL_RADIUS, ball.getY()
+ BALL_RADIUS) != null
&& getElementAt(ball.getX() + BALL_RADIUS, ball.getY()
+ BALL_RADIUS) != paddle) {
remove(getCollidingObject(ball.getX() + BALL_RADIUS, ball.getY()
+ BALL_RADIUS));
yVel = -yVel;
} else if (getElementAt(ball.getX(), ball.getY() + BALL_RADIUS) != null
&& getElementAt(ball.getX(), ball.getY() + BALL_RADIUS) != paddle) {
remove(getCollidingObject(ball.getX(), ball.getY() + BALL_RADIUS));
yVel = -yVel;
}
}
private void play() {
addMouseListeners();
ball();
while (true) {
checkForCollision();
moveBall();
pause(DELAY);
}
}
private GObject getCollidingObject(double x, double y) {
return getElementAt(x, y);
}
private double lastX;
private double lastY;
private double xVel = 5;
private double yVel = 15;
private GOval ball;
private GRect paddle;
private GObject gobj;
}
Why don't you use suggested method in handout 19:
private GObject getCollidingObject()
use also collider:
GObject collider = getCollidingObject();
First of all separate your conditions with walls collisions and (paddle with bricks) game elements collisions into two separate methods cause to simplify else if cascading (decomposition I think you know what it means). You have only two objects what you should worry about paddle and bricks, so you need to compare only on (collider == paddle) and collider != null. Also you use only radius in comparisons but should use diameter (2 * radius). Have fun :)
You're y step for each movement of the ball is too large at 15. Since each brick is only 8 in height, at times you're bypassing the brick before evaluating whether that location contained an object or not. E.g. Lets assume you're last evaluation left you're ball with a Y location of 20 and the closest brick is only length of 2 away. You're next evaluation will not include this brick since you move 15 and the height of the brick is 8, meaning range of y values 22 to 30. You'll be out by 5 away from this brick in you're next evaluation. I know the values should be inverted considering the location of the bricks, but you get the point...
With smaller steps in y values collisions will be checked more regularly and provided you make the step small enough, remove this problem.