I'm new to Java graphics, so most of this code is stuff I've gathered from the internet and injecting it into my own program. This program is meant to have a red square, controlled by the arrow keys, detect when it collides with a falling blue dot that resets to the top each time it hits the bottom.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class Surface extends JPanel implements ActionListener, KeyListener {
private final int DELAY = 8;
private Timer timer;
private Image image;
private int x, y;
private final int MOVE_AMOUNT = 5;
public final int width = 800;
public final int length = 600;
private boolean upPressed, downPressed, leftPressed, rightPressed;
;
public Surface() {
setDoubleBuffered(true);
initTimer();
loadImage();
setFocusable(true);
requestFocusInWindow();
addKeyListener(this);
x = 200;
y = 200;
}
private Image resizeImage(Image originalImage, int newWidth, int newHeight) {
return originalImage.getScaledInstance(newWidth, newHeight, Image.SCALE_SMOOTH);
}
public Rectangle getRedDotBounds() {
return new Rectangle(x, y, image.getWidth(this), image.getHeight(this));
}
private void initTimer() {
timer = new Timer(DELAY, this);
timer.start();
}
private void loadImage(){
ImageIcon ii = new ImageIcon("Basic_red_dot.png");
if (ii.getImageLoadStatus() == MediaTracker.ERRORED) {
System.out.println("Image failed to load.");
}
Image originalImage =ii.getImage();
// Resize the image to the desired dimensions
int newWidth = 75; // Set the desired width
int newHeight = 75; // Set the desired height
image = resizeImage(originalImage, newWidth, newHeight);
}
@Override
protected void paintComponent(Graphics g){
super.paintComponent(g);
g.clearRect(0, 0, getWidth(), getHeight());
drawImage(g);
}
private void drawImage(Graphics g){
g.drawImage(image, x, y, this);
}
public Timer getTimer() {
return timer;
}
public void actionPerformed(ActionEvent e) {
updatePosition();
repaint();
}
private void updatePosition(){
if (leftPressed){
x = Math.max(x-MOVE_AMOUNT, 0);
}
if(rightPressed){
x = Math.min(x + MOVE_AMOUNT, getWidth() - image.getWidth(this));
}
if(upPressed){
y = Math.max(y - MOVE_AMOUNT, 0);
}
if(downPressed){
y = Math.min(y + MOVE_AMOUNT, getHeight() - image.getHeight(this));
}
}
@Override
public void keyPressed(KeyEvent e){
int key = e.getKeyCode();
switch (key) {
case KeyEvent.VK_LEFT:
leftPressed = true;
break;
case KeyEvent.VK_RIGHT:
rightPressed = true;
break;
case KeyEvent.VK_UP:
upPressed = true;
break;
case KeyEvent.VK_DOWN:
downPressed = true;
break;
}
repaint();
}
@Override
public void keyReleased(KeyEvent e) {
int key = e.getKeyCode();
switch (key) {
case KeyEvent.VK_LEFT:
leftPressed = false;
break;
case KeyEvent.VK_RIGHT:
rightPressed = false;
break;
case KeyEvent.VK_UP:
upPressed = false;
break;
case KeyEvent.VK_DOWN:
downPressed = false;
break;
}
}
@Override
public void keyTyped(KeyEvent e) {
// Not used, but required by KeyListener
}
}
class BlueDot extends JPanel implements ActionListener {
private int x, y;
private Image image;
private final int DOT_SIZE = 10;
private final int FALL_SPEED = 1;
private Timer timer;
private int n = 0;
public BlueDot() {
setDoubleBuffered(true);
setPreferredSize(new Dimension(500, 500));
x = (int) (Math.random()*500);
y = 0;
loadImage();
timer = new Timer(10, this);
timer.start();
}
private Image resizeImage(Image originalImage, int newWidth, int newHeight) {
return originalImage.getScaledInstance(newWidth, newHeight, Image.SCALE_SMOOTH);
}
private void loadImage() {
ImageIcon ii = new ImageIcon("Basic_blue_dot.png");
if (ii.getImageLoadStatus() == MediaTracker.ERRORED) {
System.out.println("Image failed to load.");
}
Image originalImage =ii.getImage();
// Resize the image to the desired dimensions
int newWidth = 200; // Set the desired width
int newHeight = 200; // Set the desired height
image = resizeImage(originalImage, newWidth, newHeight);
}
public Rectangle getBlueDotBounds() {
return new Rectangle(x, y, DOT_SIZE, DOT_SIZE);
}
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.clearRect(0, 0, getWidth(), getHeight());
g.drawImage(image, x, y, DOT_SIZE, DOT_SIZE, this);
}
public void actionPerformed(ActionEvent e){
y += FALL_SPEED;
if (y > getHeight()) {
n++;
System.out.println("reset" + n);
x = (int) (Math.random() * 500);
y = 0;
}
//repaint();
}
}
public class MyProgram
{
public static void main(String[] args){
SwingUtilities.invokeLater(new Runnable(){
public void run() {
JFrame frame = new JFrame();
frame.setTitle("Image Display");
frame.setSize(500,500);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Surface surface = new Surface();
BlueDot blueDot = new BlueDot();
frame.setLayout(null);
surface.setBounds(0, 0, 500, 500);
frame.add(surface);
blueDot.setBounds((int) (Math.random() * 450), 0, 500, 500);
frame.add(blueDot);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
surface.requestFocusInWindow();
frame.addWindowListener(new WindowAdapter() {
@Override
public void windowOpened(WindowEvent e) {
surface.requestFocusInWindow();
}
});
Timer collisionTimer = new Timer(10, new ActionListener() {
public void actionPerformed(ActionEvent e) {
Rectangle redBounds = surface.getRedDotBounds();
Rectangle blueBounds = blueDot.getBlueDotBounds();
if (redBounds.intersects(blueBounds)) {
System.out.println("Collision!!!!");
}
}
});
collisionTimer.start();
}
});
}
}
The collision detection is a little off, mainly because the red square and the blue dot are constantly flickering. I've tried commenting out each of the three repaint statements, but that either results in one of the two elements being invisible, or some other glaring issue. How can I fix the program so this flickering goes away and the collision detection works flawlessly?
Due to @camickr requesting a more complete answer here it is. Do not stack JPanels that causes the flickering. Use a buffered image. Do not throw everything into one class but seperate code into seperate classes, think of object oriented approach.
This is abstract class ball;
package move;
import java.awt.Rectangle;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import javax.imageio.ImageIO;
import javax.swing.Timer;
public abstract class Ball
{
protected BufferedImage bufferedImage;
private int imageDiameter;
protected int x;
protected int y;
private int timerDelay;
private Timer timer;
protected int widthOfPlayingField;
public Ball(String image, int imageDiameter, int timerDelay, int xDirection,
int yDirection, int widthOfPlayingField)
{
try
{
bufferedImage = ImageIO.read(Ball.class.getResource(image));
}
catch (Exception e)
{
System.out.println("Image " + image + " failed to load.");
}
x = xDirection;
y = yDirection;
this.timerDelay = timerDelay;
this.imageDiameter = imageDiameter;
this.widthOfPlayingField = widthOfPlayingField;
}
public BufferedImage getBufferedImage()
{
return bufferedImage;
}
public Rectangle getBounds()
{
return new Rectangle(x, y, bufferedImage.getWidth(),
bufferedImage.getHeight());
}
public int getX()
{
return x;
}
public int getY()
{
return y;
}
public void initTimer(ActionListener actionListener)
{
timer = new Timer(timerDelay, actionListener);
timer.start();
}
public int getImageDiameter()
{
return imageDiameter;
}
public int getTimerDelay()
{
return timerDelay;
}
}
This is class DropBall.
package move;
import java.util.UUID;
public class DropBall extends Ball
{
private int deltaSpeed = 1;
private int resets = 0;
private UUID uuid;
public DropBall(String image, int imageDiameter, int timerDelay,
int xDirection, int yDirection, int widthOfPlayingField)
{
super(image, imageDiameter, timerDelay, xDirection, yDirection,
widthOfPlayingField);
uuid = UUID.randomUUID();
}
public void updatePosition()
{
y += deltaSpeed;
}
public UUID getUuid()
{
return uuid;
}
public void reset()
{
resets++;
System.out.println("resetting ball: " + resets + " Ball Nr. " + uuid);
x = (int) (Math.random() * widthOfPlayingField);
y = 0;
}
}
This is class MoveBall.
package move;
public class MoveBall extends Ball
{
private final int MOVE_AMOUNT = 5;
private int heightOfPlayingField;
public MoveBall(String image, int imageDiameter, int timerDelay,
int xDirection, int yDirection, int widthOfPlayingField,
int heightOfPlayingField)
{
super(image, imageDiameter, timerDelay, xDirection, yDirection,
widthOfPlayingField);
this.heightOfPlayingField = heightOfPlayingField;
}
public void updatePosition(boolean leftPressed, boolean rightPressed,
boolean upPressed, boolean downPressed)
{
if (leftPressed)
{
x = Math.max(x - MOVE_AMOUNT, 0);
}
if (rightPressed)
{
x = Math.min(x + MOVE_AMOUNT,
widthOfPlayingField - bufferedImage.getWidth());
}
if (upPressed)
{
y = Math.max(y - MOVE_AMOUNT, 0);
}
if (downPressed)
{
y = Math.min(y + MOVE_AMOUNT,
heightOfPlayingField - bufferedImage.getHeight());
}
}
}
This is class Surface.
package move;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.util.List;
import javax.swing.JPanel;
class Surface extends JPanel implements ActionListener, KeyListener
{
private static final long serialVersionUID = -1375861046489286313L;
private final int HEIGHT;
private List<DropBall> balls;
private MoveBall moveBall;
private boolean upPressed, downPressed, leftPressed, rightPressed;
public Surface(List<DropBall> balls, MoveBall moveBall, int height)
{
HEIGHT = height;
this.balls = balls;
this.moveBall = moveBall;
addKeyListener(this);
setFocusable(true);
requestFocusInWindow();
for (Ball ball : balls)
{
ball.initTimer(this);
}
moveBall.initTimer(this);
}
@Override
protected void paintComponent(Graphics g)
{
super.paintComponent(g);
for (Ball ball : balls)
{
g.drawImage(ball.getBufferedImage(), ball.getX(), ball.getY(),
ball.getImageDiameter(), ball.getImageDiameter(), this);
}
g.drawImage(moveBall.getBufferedImage(), moveBall.getX(), moveBall.getY(),
this);
}
public void actionPerformed(ActionEvent e)
{
for (DropBall ball : balls)
{
ball.updatePosition();
if (ball.getY() > HEIGHT)
{
ball.reset();
}
}
validate();
repaint();
}
@Override
public void keyPressed(KeyEvent e)
{
int key = e.getKeyCode();
switch (key)
{
case KeyEvent.VK_LEFT:
leftPressed = true;
break;
case KeyEvent.VK_RIGHT:
rightPressed = true;
break;
case KeyEvent.VK_UP:
upPressed = true;
break;
case KeyEvent.VK_DOWN:
downPressed = true;
break;
}
moveBall.updatePosition(leftPressed, rightPressed, upPressed,
downPressed);
validate();
repaint();
}
@Override
public void keyReleased(KeyEvent e)
{
int key = e.getKeyCode();
switch (key)
{
case KeyEvent.VK_LEFT:
leftPressed = false;
break;
case KeyEvent.VK_RIGHT:
rightPressed = false;
break;
case KeyEvent.VK_UP:
upPressed = false;
break;
case KeyEvent.VK_DOWN:
downPressed = false;
break;
}
}
@Override
public void keyTyped(KeyEvent e)
{
// Not used, but required by KeyListener
}
}
This is class MyProgram with main method.
package move;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JFrame;
import javax.swing.SwingUtilities;
import javax.swing.Timer;
public class MyProgram
{
private static final int HEIGHT = 500;
private static final int WIDTH = 500;
public static void main(String[] args)
{
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
JFrame frame = new JFrame();
frame.setTitle("Image Display");
frame.setSize(WIDTH, HEIGHT);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
List<DropBall> balls = new ArrayList<>();
DropBall blueBall = new DropBall("kugel_blau.png", 10, 50,
(int) (Math.random() * 500), 0, WIDTH);
balls.add(blueBall);
// here more dropping ball can be added
MoveBall moveBall = new MoveBall("kugel_rot.png", 50, 0, WIDTH / 2,
HEIGHT / 2, WIDTH, HEIGHT);
Surface surface = new Surface(balls, moveBall, HEIGHT);
frame.add(surface);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
Timer collisionTimer = new Timer(10, new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
Rectangle redBounds = moveBall.getBounds();
for (DropBall ball : balls)
{
Rectangle blueBounds = ball.getBounds();
if (redBounds.intersects(blueBounds))
{
System.out.println("Collision!!!!");
}
}
}
});
collisionTimer.start();
}
});
}
}
Have fun :-)!