We Keep Coding

Java Swing: how to react to clicking a custom JComponent?

I'm trying to make a game with ducks, the ducks are moving on the screen and I can't get a mouse click on them. I'm obviously doing something wrong because despite setting a MouseListener, its methods are not called. This is my code, I omitted getters and the DuckGame class, which is only generating ducks.
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
public class DuckGameScreen extends JPanel {
private int initialDuckNum = 7;
private final int INTERVAL = 25;
private final int INTERVAL_BTWN_DUCKS = 1000;
private Timer duckTimer;
private int ducksStarted = 0;
private DuckGame duckGame;
public DuckGameScreen() {
setBackground(Color.cyan);
askAboutDifficulty();
startTimer();
startGame();
startDifficultyIncrease();
}
private void startGame() {
duckGame = new DuckGame(initialDuckNum);
startDucks();
addDuckListeners();
}
private void addDuckListeners() {
for (Duck duck : duckGame.getDucks()) {
duck.addMouseListener(new MouseListener() {
#Override
public void mouseClicked(MouseEvent e) {}
#Override
public void mousePressed(MouseEvent e) {
System.out.println("Duck clicked");}
#Override
public void mouseReleased(MouseEvent e) {}
#Override
public void mouseEntered(MouseEvent e) {}
#Override
public void mouseExited(MouseEvent e) {}
});
}
}
#Override
public void paint(Graphics g) {
super.paint(g);
drawDucks(g);
Toolkit.getDefaultToolkit().sync();
}
private void animateDuck(Duck duck) {
new Thread() {
#Override
public void run() {
super.run();
while (!duck.isDuckStopped()) {
try {
Thread.sleep(INTERVAL);
duck.move();
if (duck.getX() - duck.getWidth() >= Toolkit.getDefaultToolkit().getScreenSize().width) {
duck.resetPosition();
}
repaint();
} catch (InterruptedException e) {
e.printStackTrace();
duck.stop();
break;
}
}
}
}
.start();
}
private void drawDucks(Graphics g) {
for (Duck duck : duckGame.getDucks()) {
duck.paintComponent(g);
}
}
}
And my Duck class:
public class Duck extends JComponent {
private final static int INIT_X = -100;
private int x = INIT_X;
private int y = 100;
private int width = 0;
private int height = 0;
private Image image = null;
private boolean isDuckStopped = false;
private final int STEP = 5;
public Duck() {
initRandomPosition();
loadImage();
setVisible(true);
setBounds(x, y, width, height);
}
private void initRandomPosition() {
y = getRandomY();
}
public void move() {
x += STEP;
}
private void loadImage() {
ImageIcon imageIcon = new ImageIcon(getFilePath(Images.DUCK.getFileName()));
Dimension newDimension = Utils.getScaledDimension(100, 100, imageIcon.getIconWidth(), imageIcon.getIconHeight());
image = imageIcon.getImage().getScaledInstance(newDimension.width, newDimension.height, Image.SCALE_DEFAULT);
width = image.getWidth(null);
height = image.getHeight(null);
}
#Override
public void paintComponent(Graphics g) {
super.paintComponents(g);
drawDuck(g);
Toolkit.getDefaultToolkit().sync();
}
private void drawDuck(Graphics g) {
Graphics2D g2D = (Graphics2D) g;
g2D.drawImage(image, x, y, this);
setBounds(x, y, width, height);
}
public void stop() {
isDuckStopped = true;
setVisible(false);
}
public void resetPosition() {
x = INIT_X;
y = getRandomY();
}
}

Why is java copying instead of creating a new Instant When i use different variables?

I made a fairly simple code and i got into an error which confused me.
So I have a class that creates two totally different variables and creating them using the new keyword
Player playerLeft = new Player(5,150);
Player playerRight = new Player( 150,150);
Player class:
import javax.swing.*;
import java.awt.*;
public class Player extends JComponent {
private int posY;
private int posX;
public Player(int x, int y) {
posX = x;
posY = y;
//repaint();
}
public float getMovementY() {
return movementY;
}
public void setMovementY(int movementY) {
this.movementY = movementY;
}
int movementY = 0;
public void paintComponent(Graphics g) {
Graphics2D _g2 = (Graphics2D) g;
Rectangle rect = new Rectangle(posX, posY, 20, 150);
_g2.fill(rect);
}
public void setLocation(int x, int y) {
posY = y;
posX = x;
repaint();
}
public void move() {
setLocation(posX, posY + movementY);
}
}
It's probably me not knowing something about Java but for me when I try to instantiate playerRight it just overwrites player left and drawsOut playerRight only.
Here is the complete code:
import javax.swing.*;
import java.awt.*;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.util.Timer;
import java.util.TimerTask;
public class mainJFrame extends JFrame implements KeyListener {
int relativeTimeMillsec = 0;
Player playerLeft = new Player(5, 150);
Player playerRight = new Player(150, 150);
Timer timer = new Timer();
TimerTask task = new TimerTask() {
#Override
public void run() {
relativeTimeMillsec++;
refreshTimeText(relativeTimeMillsec);
calcMovements();
}
};
//components
JLabel timeCounterLabel = new JLabel("Time: " + 0, SwingConstants.CENTER);
public mainJFrame() {
createComponents();
addKeyListener(this);
}
public void createComponents() {
this.setTitle("The title");
this.setSize(800, 600);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setVisible(true);
timer.scheduleAtFixedRate(task, 0, 10);
JButton testButton = new JButton("Label");
testButton.setSize(100, 25);
testButton.setLocation(this.getWidth() / 2 - testButton.getWidth() / 2, this.getHeight() / 2 - testButton.getHeight() / 2);
timeCounterLabel.setSize(200, 25);
timeCounterLabel.setLocation(this.getWidth() / 2 - timeCounterLabel.getWidth() / 2, 10);
//playerRight = new Player(this.getWidth()-45,this.getHeight()/2);
// this.add(testButton);
this.add(timeCounterLabel);
this.add(playerLeft);
this.add(playerRight);
}
public void paintComponent(Graphics g) {
{
super.repaint();
}
}
#Override
public void keyPressed(KeyEvent e) {
if (e.getKeyCode() == KeyEvent.VK_S) {
playerLeft.movementY = +2;
} else if (e.getKeyCode() == KeyEvent.VK_W) {
playerLeft.movementY = -2;
}
if (e.getKeyCode() == KeyEvent.VK_UP) {
playerRight.movementY = +2;
} else if (e.getKeyCode() == KeyEvent.VK_DOWN) {
playerRight.movementY = -2;
}
}
#Override
public void keyReleased(KeyEvent e) {
}
#Override
public void keyTyped(KeyEvent e) {
}
private double calcRealRelativeTime(int _relTime) {
return relativeTimeMillsec / (double) 100;
}
private void refreshTimeText(int _relTime) {
timeCounterLabel.setText("Time: " + Math.round(calcRealRelativeTime(_relTime)));
}
private void calcMovements() {
playerLeft.move();
playerRight.move();
}
}

Understand that a JFrame's contentPane (the container that holds its components) uses BorderLayout by default, and this code:
this.add(timeCounterLabel);
this.add(playerLeft);
this.add(playerRight);
is adding all components to the same default BorderLayout.CENTER position, meaning any components added will replace components added previously.
But more importantly, yours is a common problem and stems from your having your Player class extend from a GUI component. Don't do this, as then you will have a great deal of difficulty drawing multiple Player objects and having them interact easily (as you're finding out). Instead have Player be a logical (non-component) class, and have only one class extend JPanel and do all the drawing. This class can hold Player objects, perhaps held in a collection such as an ArrayList<Player>, and then iterate through the collection within its paintComponent method.
Other issues:
Do not use java.util.Timer and java.util.TimerTask for Swing animations since these classes do not follow Swing threading rules. Use instead a javax.swing.Timer.
Learn and use Java naming conventions. Variable names should all begin with a lower letter while class names with an upper case letter. Learning this and following this will allow us to better understand your code, and would allow you to better understand the code of others
If/when you do override a painting method such as paintComponent, be sure to call the super's method within your override, usually on the first line, so as not to break the painting chain. Also, use the #Override annotation before this method and any other methods that you think that you may be overriding so that the compiler catches possible errors with this.
For example (but not a complete example)
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
#SuppressWarnings("serial")
public class SimpleAnimation extends JPanel {
private static final int PREF_W = 800;
private static final int PREF_H = 600;
private static final int TIMER_DELAY = 20;
private Player2 playerLeft = new Player2(5, 150, Color.RED);
private Player2 playerRight = new Player2(150, 150, Color.BLUE);
public SimpleAnimation() {
playerLeft.setySpeed(1);
playerRight.setySpeed(-1);
new Timer(TIMER_DELAY, new TimerListener()).start();
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
playerLeft.draw(g);
playerRight.draw(g);
}
#Override
public Dimension getPreferredSize() {
if (isPreferredSizeSet()) {
return super.getPreferredSize();
}
return new Dimension(PREF_W, PREF_H);
}
private class TimerListener implements ActionListener {
#Override
public void actionPerformed(ActionEvent e) {
playerRight.move();
playerLeft.move();
repaint();
}
}
private static void createAndShowGui() {
SimpleAnimation mainPanel = new SimpleAnimation();
JFrame frame = new JFrame("SimpleAnimation");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> createAndShowGui());
}
}
class Player2 {
private static final int RECT_WIDTH = 20;
private static final int RECT_HEIGHT = 50;
private int x;
private int y;
private int ySpeed;
private Color color;
public Player2(int x, int y, Color color) {
this.x = x;
this.y = y;
this.color = color;
}
public void setX(int x) {
this.x = x;
}
public void setY(int y) {
this.y = y;
}
public int getX() {
return x;
}
public int getY() {
return y;
}
public void setySpeed(int ySpeed) {
this.ySpeed = ySpeed;
}
public int getySpeed() {
return ySpeed;
}
public void setLocation(int x, int y) {
setX(x);
setY(y);
}
public void move() {
setLocation(x, y + ySpeed);
}
public void draw(Graphics g) {
g.setColor(color);
g.fillRect(x, y, RECT_WIDTH, RECT_HEIGHT);
}
}

Changing color with KeyListener

I have a project that a circle goes with random x and y values and with selected colors but when the user pressed the space bar the color of the circle must be changed. My circle moves both x and y coordinate and I want to change the color of the circle when I press the space button. But it does not work when I pressed it. It goes with its original color. So how can I make this code right?
public class c {
private int x,y,r;
private Color co;
private int Re,G,B;
private Random ran;
public c() {
// TODO Auto-generated constructor stub
ran= new Random();
x=100;
y=50;
r= ran.nextInt(200)+50;
Re=ran.nextInt(255);
G=ran.nextInt(255);
B=ran.nextInt(255);
co= new Color(Re,G,B);
}
public int getRe() {
return Re;
}
public int getG() {
return G;
}
public int getB() {
return B;
}
public int getX() {
return x;
}
public int getY() {
return y;
}
public int getR() {
return r;
}
public void setCo(int Re,int G,int B) {
co= new Color(Re,G,B);
}
public Color getCo() {
return co;
}
public Random getRan() {
return ran;
}
public void setX(int x) {
this.x=x;
}
public void setY(int y) {
this.y=y;
}
}
public class Circle extends JFrame implements ActionListener,KeyListener{
private Timer timer;
private int x,y,a=5,b=5;
private Random rand;
c circ = new c();
public Circle() {
setLayout(new BorderLayout());
x=circ.getX();
y=circ.getY();
timer=new Timer(50,this);
timer.start();
addKeyListener(this);
setSize(550,550);
setVisible(true);
}
public void paint(Graphics g) {
super.paint(g);
g.fillOval(x,y,100,100);
g.setColor(circ.getCo());
}
public static void main(String[]args) {
new Circle();
}
#Override
public void actionPerformed(ActionEvent e) {
moveWithTimer();
repaint();
}
public void moveWithTimer() {
x=x+b;
y=y+a;
if(x<0) {
b=5;
}
if(x+50>500) {
b=-5;
}
if(y<0){
a=5;
}
if(y+50>500) {
a=-5;
}
}
#Override
public void keyPressed(KeyEvent e) {
// TODO Auto-generated method stub
if(e.getKeyCode()==e.VK_SPACE) {
circ.setCo(rand.nextInt(255),rand.nextInt(255),rand.nextInt(255));
}
}
#Override
public void keyReleased(KeyEvent e) {
// TODO Auto-generated method stub
}
#Override
public void keyTyped(KeyEvent e) {
// TODO Auto-generated method stub
}
}

But it does not work when I pressed it. It goes with its original color. So how can I make this code right?
KeyListener is fickle, better to use the Key Bindings API which overcomes the primary, focus related, issues of KeyListener
As a general rule of thumb, you shouldn't override paint of top level containers like JFrame, they are compound components and it's just a real mess.
Instead, start with a JPanel and override it's paintComponent method. It's generally more flexible. Have a look at Performing Custom Painting for more details.
Your movement code is wrong. You assign the x/y values of the circle class to some other variables, the problem here is, changing the values of these variables will have no affect on the variables in you circle class, instead, you need assign them back...
public void moveWithTimer() {
int x = circ.getX();
int y = circ.getY();
x = x + b;
y = y + a;
if (x < 0) {
b = 5;
}
if (x + 50 > 500) {
b = -5;
}
if (y < 0) {
a = 5;
}
if (y + 50 > 500) {
a = -5;
}
circ.setX(x);
circ.setY(y);
}
Your "circle" class could also use a couple of additional methods. One to randomise the color (it already has a Random object, might as well use it) and one to paint the object.
public class Circle {
//...
public void paint(Graphics2D g2d) {
g2d.setColor(co);
g2d.fillOval(x, y, r * 2, r * 2);
}
//...
public void randomColor() {
setCo(ran.nextInt(255), ran.nextInt(255), ran.nextInt(255));
}
//...
}
If it was me, I'd be tempted to add a move method as well, but that's me ;)
As a 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.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.util.Random;
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;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class Test {
public static void main(String[] args) {
new Test();
}
public Test() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private Timer timer;
private int a = 5, b = 5;
private Random rand;
private Circle circ = new Circle();
public TestPane() {
timer = new Timer(50, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
moveWithTimer();
repaint();
}
});
timer.start();
InputMap im = getInputMap(WHEN_IN_FOCUSED_WINDOW);
ActionMap am = getActionMap();
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_SPACE, 0), "spaced");
am.put("spaced", new AbstractAction() {
#Override
public void actionPerformed(ActionEvent e) {
circ.randomColor();
repaint();
}
});
}
public void moveWithTimer() {
int x = circ.getX();
int y = circ.getY();
x = x + b;
y = y + a;
if (x < 0) {
b = 5;
}
if (x + 50 > 500) {
b = -5;
}
if (y < 0) {
a = 5;
}
if (y + 50 > 500) {
a = -5;
}
circ.setX(x);
circ.setY(y);
}
#Override
public Dimension getPreferredSize() {
return new Dimension(500, 500);
}
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
circ.paint(g2d);
g2d.dispose();
}
}
public class Circle {
private int x, y, r;
private Color co;
private int Re, G, B;
private Random ran;
public Circle() {
// TODO Auto-generated constructor stub
ran = new Random();
x = 100;
y = 50;
r = ran.nextInt(50) + 50;
Re = ran.nextInt(255);
G = ran.nextInt(255);
B = ran.nextInt(255);
co = new Color(Re, G, B);
}
public void paint(Graphics2D g2d) {
g2d.setColor(co);
g2d.fillOval(x, y, r * 2, r * 2);
}
public int getRe() {
return Re;
}
public int getG() {
return G;
}
public int getB() {
return B;
}
public int getX() {
return x;
}
public int getY() {
return y;
}
public int getR() {
return r;
}
public void randomColor() {
setCo(ran.nextInt(255), ran.nextInt(255), ran.nextInt(255));
}
public void setCo(int Re, int G, int B) {
co = new Color(Re, G, B);
}
public Color getCo() {
return co;
}
public Random getRan() {
return ran;
}
public void setX(int x) {
this.x = x;
}
public void setY(int y) {
this.y = y;
}
}
}

I suggest you should set the color of the graphics object within paint(g) before painting the circle.
public void paint(Graphics g) {
super.paint(g);
g.setColor(circ.getCo());
g.fillOval(x,y,100,100);
}
In general, you should not override the paint() method of the JFrame. Instead, create a JPanel, add it to your frame and override the paintComponent() method of the panel.

Key Ghosting Problems

I am making a game and I ran into a key ghosting problem (where the program only detects one keypress at a time, so the player can't go diagonally). I was watching this tutorial: https://www.youtube.com/watch?v=5UaEUrbpDPE
I followed everything they said and it still only detects one key at a time.
Main:
public class Main extends JApplet implements Runnable, KeyListener {
private static final long serialVersionUID = 1L;
public static int width = 900;
public static int height = 600;
public static int fps = 60;
public static Main instance;
public static Ailoid ailoid = new Ailoid();
public static Player player = new Player();
// Initialize
public void init() {
setSize(width, height);
setBackground(Color.white);
addKeyListener(this);
setFocusable(true);
setFocusTraversalKeysEnabled(false);
requestFocus();
instance = this;
ailoid.setLocation(new Location(100, 100));
AlienManager.registerAlien(ailoid);
player.setLocation(new Location(400, 400));
}
// Paint graphics
public void paint(Graphics g) {
super.paint(g);
paintComponent(g);
}
public void paintComponent(Graphics g) {
for (Alien alien : AlienManager.getAliens()) {
Location loc = alien.getLocation();
g.setColor(Color.GREEN);
g.fillRect(loc.getX(), loc.getY(), 10, 25);
}
g.setColor(Color.BLUE);
Location loc = Main.player.getLocation();
g.fillRect(loc.getX(), loc.getY(), 10, 25);
}
// Thread start
#Override
public void start() {
Thread thread = new Thread(this);
thread.start();
}
// Thread stop
#Override
public void destroy() {
}
// Thread run
#Override
public void run() {
Thread thread = new Thread(this);
while (thread != null) {
Updater.run();
repaint();
try {
// 1000 divided by fps to get frames per second
Thread.sleep(1000 / fps);
}
catch (InterruptedException e) {
e.printStackTrace();
}
}
}
#Override
public void keyPressed(KeyEvent evt) {
if (!KeysDown.get().contains(evt.getKeyCode()))
KeysDown.add(new Integer(evt.getKeyCode()));
KeyPress.run(evt);
}
#Override
public void keyReleased(KeyEvent evt) {
KeysDown.remove(new Integer(evt.getKeyCode()));
}
#Override
public void keyTyped(KeyEvent evt) {
}
}
KeysDown:
public class KeysDown {
private static ArrayList<Integer> keysDown = new ArrayList<Integer>();
public static ArrayList<Integer> get() {
return keysDown;
}
public static void add(Integer key) {
keysDown.add(key);
}
public static void remove(Integer key) {
keysDown.remove(key);
}
}
KeyPress:
public class KeyPress {
public static void run(KeyEvent evt) {
if (KeysDown.get().contains(KeyEvent.VK_RIGHT)) {
Main.player.moveRight();
}
else if (KeysDown.get().contains(KeyEvent.VK_LEFT)) {
Main.player.moveLeft();
}
else if (KeysDown.get().contains(KeyEvent.VK_DOWN)) {
Main.player.moveDown();
}
else if (KeysDown.get().contains(KeyEvent.VK_UP)) {
Main.player.moveUp();
}
}
}
Thank you!

Again as I have mentioned in previous comments:
Don't draw directly on the JApplet or in any top-level window.
If you give your applet a paintComponent method, it won't override any applet methods and won't gain the benefit of double buffering.
Instead draw in the paintComponent method of a JPanel, an thereby gain the benefit of double buffering.
Use Key Bindings not a KeyListener.
Also, I like to use a Swing Timer for simple game loops.
In the code below, I use an enum called Direction to encapsulate the idea of directions on the screen.
I then put the for Directions together with Boolean.FALSE in a Map<Direction, Boolean> called dirMap.
I run a Swing Timer continuously, polling the state of this Map and move a sprite based on the state of Booleans held by the dirMap.
I change the state of the map held values in my Key Binding Actions. So if the down key is pressed, its action will change the Direction.DOWN associated value in the Map to true, and when released, the Direction.DOWN associated value will be changed back to false.
For example:
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.EnumMap;
import javax.imageio.ImageIO;
import javax.swing.*;
#SuppressWarnings("serial")
public class AnimateExample extends JPanel {
public static final String DUKE_IMG_PATH = // https://duke.kenai.com/iconSized/duke.gif
"https://duke.kenai.com/iconSized/duke4.gif";
private static final int PREF_W = 800;
private static final int PREF_H = 800;
private static final int TIMER_DELAY = 20;
private static final String KEY_DOWN = "key down";
private static final String KEY_RELEASE = "key release";
public static final int TRANSLATE_SCALE = 3;
private static final String BACKGROUND_STRING = "Use Arrow Keys to Move Image";
private static final Font BG_STRING_FONT = new Font(Font.SANS_SERIF,
Font.BOLD, 32);
private EnumMap<Direction, Boolean> dirMap =
new EnumMap<AnimateExample.Direction, Boolean>(Direction.class);
private BufferedImage image = null;
private int imgX = 0;
private int imgY = 0;
private int bgStringX;
private int bgStringY;
public AnimateExample() {
for (Direction dir : Direction.values()) {
dirMap.put(dir, Boolean.FALSE);
}
try {
URL imgUrl = new URL(DUKE_IMG_PATH);
image = ImageIO.read(imgUrl);
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
new Timer(TIMER_DELAY, new TimerListener()).start();
// here we set up our key bindings
int condition = JComponent.WHEN_IN_FOCUSED_WINDOW;
InputMap inputMap = getInputMap(condition);
ActionMap actionMap = getActionMap();
for (final Direction dir : Direction.values()) {
// for the key down key stroke
KeyStroke keyStroke = KeyStroke.getKeyStroke(dir.getKeyCode(), 0,
false);
inputMap.put(keyStroke, dir.name() + KEY_DOWN);
actionMap.put(dir.name() + KEY_DOWN, new AbstractAction() {
#Override
public void actionPerformed(ActionEvent arg0) {
dirMap.put(dir, true);
}
});
// for the key release key stroke
keyStroke = KeyStroke.getKeyStroke(dir.getKeyCode(), 0, true);
inputMap.put(keyStroke, dir.name() + KEY_RELEASE);
actionMap.put(dir.name() + KEY_RELEASE, new AbstractAction() {
#Override
public void actionPerformed(ActionEvent arg0) {
dirMap.put(dir, false);
}
});
}
FontMetrics fontMetrics = getFontMetrics(BG_STRING_FONT);
int w = fontMetrics.stringWidth(BACKGROUND_STRING);
int h = fontMetrics.getHeight();
bgStringX = (PREF_W - w) / 2;
bgStringY = (PREF_H - h) / 2;
}
#Override
public Dimension getPreferredSize() {
return new Dimension(PREF_W, PREF_H);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g.setFont(BG_STRING_FONT);
g.setColor(Color.LIGHT_GRAY);
g2.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING,
RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
g.drawString(BACKGROUND_STRING, bgStringX, bgStringY);
if (image != null) {
g.drawImage(image, imgX, imgY, this);
}
}
private class TimerListener implements ActionListener {
public void actionPerformed(java.awt.event.ActionEvent e) {
for (Direction dir : Direction.values()) {
if (dirMap.get(dir)) {
imgX += dir.getX() * TRANSLATE_SCALE;
imgY += dir.getY() * TRANSLATE_SCALE;
}
}
repaint();
};
}
enum Direction {
Up(KeyEvent.VK_UP, 0, -1), Down(KeyEvent.VK_DOWN, 0, 1), Left(
KeyEvent.VK_LEFT, -1, 0), Right(KeyEvent.VK_RIGHT, 1, 0);
private int keyCode;
private int x;
private int y;
private Direction(int keyCode, int x, int y) {
this.keyCode = keyCode;
this.x = x;
this.y = y;
}
public int getKeyCode() {
return keyCode;
}
public int getX() {
return x;
}
public int getY() {
return y;
}
}
private static void createAndShowGui() {
AnimateExample mainPanel = new AnimateExample();
JFrame frame = new JFrame("Animate Example");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
For more on Key Bindings, please check out the informative tutorial which you can find here.

Java KeyEvent square movement

I have a piece of code in which a KeyEvent is triggered when any of the arrow keys are pressed. This in turn causes a square to move across the screen.
Now I've noticed that when I press and hold the key, the square moves but the time after the initial movement to the subsequent movements is quite long if you understand what I mean? How would I go about diminishing this time?
Thanks!
import java.awt.*;
import javax.swing.*;
import squarequest.sprites.*;
import java.awt.event.*;
public class GamePanel extends JPanel{
private final int HEIGHT = 400;
private final int WIDTH = 600;
private Square square;
private Circle circle;
public GamePanel(){
addKeyListener(new DirectionListener());
setBackground (Color.white);
setPreferredSize(new Dimension(WIDTH, HEIGHT));
setFocusable(true);
square = new Square();
}
public void paintComponent(Graphics g){
super.paintComponent(g);
square.display(g);
}
public class DirectionListener implements KeyListener{
#Override
public void keyReleased(KeyEvent event) {}
#Override
public void keyTyped(KeyEvent event) {}
#Override
public void keyPressed(KeyEvent event) {
switch(event.getKeyCode()){
case KeyEvent.VK_UP:
square.moveUp();
break;
case KeyEvent.VK_DOWN:
square.moveDown();
break;
case KeyEvent.VK_LEFT:
square.moveLeft();
break;
case KeyEvent.VK_RIGHT:
square.moveRight();
break;
}
repaint();
}
}
}

Use a Swing Timer for the actual movement.
Start the Timer on key press
Stop it on key release.
Or better still, keep the timer always running, but only moving the sprite based on the state of a map, one that holds a Direction enum key and a Boolean value.
Better to use key bindings rather than KeyListeners.
e.g.,
import java.awt.*;
import javax.swing.*;
//!! import squarequest.sprites.*;
import java.awt.event.*;
import java.util.EnumMap;
import java.util.HashMap;
import java.util.Map;
public class GamePanel extends JPanel {
private static final int ANIMATION_DELAY = 15;
private final int HEIGHT = 400;
private final int WIDTH = 600;
private Square square;
private EnumMap<Direction, Boolean> dirMap = new EnumMap<>(Direction.class);
private Map<Integer, Direction> keyToDir = new HashMap<>();
// !! private Circle circle;
private Timer animationTimer;
public GamePanel() {
for (Direction dir : Direction.values()) {
dirMap.put(dir, Boolean.FALSE);
}
keyToDir.put(KeyEvent.VK_UP, Direction.UP);
keyToDir.put(KeyEvent.VK_DOWN, Direction.DOWN);
keyToDir.put(KeyEvent.VK_LEFT, Direction.LEFT);
keyToDir.put(KeyEvent.VK_RIGHT, Direction.RIGHT);
// !! addKeyListener(new DirectionListener());
setKeyBindings();
setBackground(Color.white);
setPreferredSize(new Dimension(WIDTH, HEIGHT));
setFocusable(true);
square = new Square();
animationTimer = new Timer(ANIMATION_DELAY, new AnimationListener());
animationTimer.start();
}
private void setKeyBindings() {
int condition = WHEN_IN_FOCUSED_WINDOW;
final InputMap inputMap = getInputMap(condition);
final ActionMap actionMap = getActionMap();
boolean[] keyPressed = { true, false };
for (Integer keyCode : keyToDir.keySet()) {
Direction dir = keyToDir.get(keyCode);
for (boolean onKeyPress : keyPressed) {
boolean onKeyRelease = !onKeyPress; // to make it clear how bindings work
KeyStroke keyStroke = KeyStroke.getKeyStroke(keyCode, 0,
onKeyRelease);
Object key = keyStroke.toString();
inputMap.put(keyStroke, key);
actionMap.put(key, new KeyBindingsAction(dir, onKeyPress));
}
}
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
square.display(g);
}
// public class DirectionListener implements KeyListener {
// #Override
// public void keyReleased(KeyEvent event) {
// int keyCode = event.getKeyCode();
// if (keyToDir.keySet().contains(keyCode)) {
// Direction dir = keyToDir.get(keyCode);
// dirMap.put(dir, false);
// }
// }
//
// #Override
// public void keyTyped(KeyEvent event) {
// }
//
// #Override
// public void keyPressed(KeyEvent event) {
// int keyCode = event.getKeyCode();
// if (keyToDir.keySet().contains(keyCode)) {
// Direction dir = keyToDir.get(keyCode);
// dirMap.put(dir, true);
// }
// }
// }
private class AnimationListener implements ActionListener {
#Override
public void actionPerformed(ActionEvent evt) {
boolean repaint = false;
for (Direction dir : Direction.values()) {
if (dirMap.get(dir)) {
square.move(dir);
repaint = true;
}
}
if (repaint) {
repaint();
}
}
}
private class KeyBindingsAction extends AbstractAction {
private Direction dir;
boolean pressed;
public KeyBindingsAction(Direction dir, boolean pressed) {
this.dir = dir;
this.pressed = pressed;
}
#Override
public void actionPerformed(ActionEvent evt) {
dirMap.put(dir, pressed);
}
}
private static void createAndShowGUI() {
GamePanel gamePanel = new GamePanel();
JFrame frame = new JFrame("GamePanel");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(gamePanel);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
gamePanel.requestFocusInWindow();
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
}
enum Direction {
UP(0, -1), DOWN(0, 1), LEFT(-1, 0), RIGHT(1, 0);
private int incrX;
private int incrY;
private Direction(int incrX, int incrY) {
this.incrX = incrX;
this.incrY = incrY;
}
public int getIncrX() {
return incrX;
}
public int getIncrY() {
return incrY;
}
}
class Square {
private int x = 0;
private int y = 0;
private int w = 20;
private int h = w;
private int step = 1;
private Color color = Color.red;
private Color fillColor = new Color(255, 150, 150);
private Stroke stroke = new BasicStroke(3f, BasicStroke.CAP_ROUND,
BasicStroke.JOIN_ROUND);
public void display(Graphics g) {
Graphics2D g2d = (Graphics2D) g.create();
g2d.setColor(fillColor);
g2d.fillRect(x, y, w, h);
g2d.setStroke(stroke);
g2d.setColor(color);
g2d.drawRect(x, y, w, h);
g2d.dispose();
}
public void setStep(int step) {
this.step = step;
}
public void move(Direction dir) {
x += step * dir.getIncrX();
y += step * dir.getIncrY();
}
// public void moveRight() {
// x++;
// }
//
// public void moveLeft() {
// x--;
// }
//
// public void moveUp() {
// y--;
// }
//
// public void moveDown() {
// y++;
// }
}