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Learning KeyEvents

I am relatively new to java and was trying to learn how to make a program where there is this circle and I can move it around using the arrow keys. After shifting through a bunch of examples I was able to put something together. Although I am unsure how to create a KeyEvent. Any help with what I am missing would be awesome.
This is what I have so far.
import javax.swing.WindowConstants;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.Color;
import java.awt.event.KeyEvent;
#SuppressWarnings("serial")
public class Game extends JPanel
{
int x = 0;
int y = 0;
private void moveBallUP() {
x = x + 0;
y = y + 1;
}
private void moveBallDOWN() {
x = x + 0;
y = y - 1;
}
private void moveBallLEFT() {
x = x + 1;
y = y + 0;
}
private void moveBallRIGHT() {
x = x - 1;
y = y + 0;
}
#Override
public void paint(Graphics g)
{
super.paint(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
g.setColor(Color.red);
g2d.fillOval(y, x, 50, 50);
}
public static void main(String[] args) throws InterruptedException
{
JFrame frame = new JFrame("Sample Frame");
Game game = new Game();
frame.add(game);
frame.setSize(300, 400);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
if (event.getKeyCode() == KeyEvent.VK_UP)
{
game.moveBallUP();
game.repaint();
Thread.sleep(10);
}
if (event.getKeyCode() == KeyEvent.VK_DOWN)
{
game.moveBallDOWN();
game.repaint();
Thread.sleep(10);
}
if (event.getKeyCode() == KeyEvent.VK_LEFT)
{
game.moveBallLEFT();
game.repaint();
Thread.sleep(10);
}
if (event.getKeyCode() == KeyEvent.VK_RIGHT)
{
game.moveBallRIGHT();
game.repaint();
Thread.sleep(10);
}
}
}

There are several steps to solving this: first, use a KeyListener. Add the following code to the Game class; this will represent which buttons are pressed:
private boolean upPressed=false;
private boolean downPressed=false;
private boolean leftPressed=false;
private boolean rightPressed=false;
Then, add this to the main method:
frame.addKeyListener(new KeyListener() {
#Override
public void keyReleased(KeyEvent event) {
switch (event.getKeyCode()) {
case KeyEvent.VK_UP:
game.upPressed=false;
break;
case KeyEvent.VK_DOWN:
game.downPressed=false;
break;
case KeyEvent.VK_LEFT:
game.leftPressed=false;
break;
case KeyEvent.VK_RIGHT:
game.rightPressed=false;
break;
}
}
#Override
public void keyTyped(KeyEvent event) {
}
#Override
public void keyPressed(KeyEvent event) {
switch (event.getKeyCode()) {
case KeyEvent.VK_UP:
game.upPressed=true;
break;
case KeyEvent.VK_DOWN:
game.downPressed=true;
break;
case KeyEvent.VK_LEFT:
game.leftPressed=true;
break;
case KeyEvent.VK_RIGHT:
game.rightPressed=true;
break;
}
}
});
Basically, you are setting the variables we created to true when the buttons are pressed down and false when they are released. Finally, add a Timer in the main method:
Timer timer = new Timer(10,(e)->{
if (game.upPressed)
{
game.moveBallUP();
game.repaint();
}
if (game.downPressed)
{
game.moveBallDOWN();
game.repaint();
}
if (game.leftPressed)
{
game.moveBallLEFT();
game.repaint();
}
if (game.rightPressed)
{
game.moveBallRIGHT();
game.repaint();
}
});
timer.start();
This will fire every 10 milliseconds and call your move methods if the buttons are pressed.
I have tested this and know that it works, however your move methods move the circle in the wrong directions. I assume you can fix that.
EDIT: The mistake is in this line:
g2d.fillOval(y, x, 50, 50);
Change it to:
g2d.fillOval(x,y , 50, 50);

How to see if a keyboard key is pressed without using text fields?

I am trying to create a very simple game that moves a ball up/right/left/down if you press the keys up/right/left/down. I looked up at different places, and here is what I made:
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.Toolkit;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JFrame;
import javax.swing.JPanel;
#SuppressWarnings("serial")
public class Game extends JPanel implements KeyListener {
static Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
static int width = (int)screenSize.getWidth();
static int height = (int)screenSize.getHeight();
static int x = width/2;
static int y = height/2;
boolean a=true;
boolean b=true;
public void keyTyped(KeyEvent e){
//nothing here
}
public void keyPressed(KeyEvent e) {
int keyCode = e.getKeyCode();
switch( keyCode ) {
case KeyEvent.VK_UP:
x=x+10;
case KeyEvent.VK_DOWN:
x=x-10;
case KeyEvent.VK_LEFT:
y=y+10;
case KeyEvent.VK_RIGHT :
y=y-10;
}
}
public void keyReleased(KeyEvent e){
//nothing here
}
#Override
public void paint(Graphics g) {
super.paint(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
g2d.fillOval(x, y, 30, 30);
}
public static void main(String[] args)throws InterruptedException {
JFrame frame = new JFrame("Sample");
Game game = new Game();
frame.add(game);
frame.setSize(width,height);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
while (true) {
game.keyPressed(null);
game.repaint();
}
}
}
But how do I "run" the keyPressed program? I saw some YouTube videos that said do something like"addKeyListener" or "addActionListener", but that mean adding a text field, text box, or text area, which I don't want. This is suppose to resemble a game after all. Thanks
edited version after looking at answers:
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.Toolkit;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JFrame;
import javax.swing.JPanel;
#SuppressWarnings("serial")
public class Game extends JPanel implements KeyListener {
static Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
static int width = (int)screenSize.getWidth();
static int height = (int)screenSize.getHeight();
static int x = width/2;
static int y = height/2;
boolean a=true;
boolean b=true;
static Game game;
public Game(){
addKeyListener(this);
}
public void keyTyped(KeyEvent e){
//nothing here
}
#Override
public void keyReleased(KeyEvent e) {
// nothing here
}
public void keyPressed(KeyEvent e) {
int keyCode = e.getKeyCode();
switch( keyCode ) {
case KeyEvent.VK_UP:
x=x+100;
case KeyEvent.VK_DOWN:
x=x-100;
case KeyEvent.VK_LEFT:
y=y+100;
case KeyEvent.VK_RIGHT :
y=y-1000;
}
game.repaint();
}
#Override
public void paint(Graphics g) {
super.paint(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
g2d.fillOval(x, y, 30, 30);
}
public static void main(String[] args)throws InterruptedException {
JFrame frame = new JFrame("Sample");
game = new Game();
frame.add(game);
frame.setSize(width,height);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}

In your constructor , add
Game()
{
/*your code*/
addKeyListener(this);
}

You can add the keylistener to your Game object during construction.
addKeyListener(new KeyAdapter()
{
#Override
public void keyPressed(KeyEvent e)
{
myKeyEvt(e, "keyPressed");
}
private void myKeyEvt(KeyEvent e, String text)
{
int key = e.getKeyCode();
if (key == KeyEvent.VK_KP_UP || key == KeyEvent.VK_UP)
{
//up
}
else if (key == KeyEvent.VK_KP_DOWN || key == KeyEvent.VK_DOWN)
{
//down
}
else if (key == KeyEvent.VK_KP_LEFT || key == KeyEvent.VK_LEFT)
{
//left
}
else if (key == KeyEvent.VK_KP_RIGHT|| key == KeyEvent.VK_RIGHT)
{
//right
}
}
});
Also, you will want to update your while loop to give it time to pause and refresh
while (alive)
{
update();
repaint();
try
{
Thread.sleep(100);
}
catch (InterruptedException e)
{
e.printStackTrace();
}
}

Java ping pong game (form youtube tutorial), paddles doesn't work

I made a ping pong game in Java but the paddles doesn't work, and I can't figure out the problem.
Main class: in the main class I give the thread and run the program:
package pingpong;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import javax.swing.*;
public class PingPong extends JFrame {
int Gwidth=400,Gheight=300;
Dimension screenSize = new Dimension(Gwidth,Gheight);
//double Buffering
Image dbImage;
Graphics dbg;
//ball objects
static Ball b = new Ball(193,143);
//constructor
public PingPong() {
this.setTitle("ping pong Game");
this.setResizable(false);
this.setSize(screenSize);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setBackground(Color.black);
this.setVisible(true);
}
#Override
public void paint(Graphics g) {
dbImage = createImage(getWidth(), getHeight());
dbg = dbImage.getGraphics();
draw(dbg);
g.drawImage(dbImage, 0, 0, this);
}
public void draw(Graphics g) {
b.draw(g);
b.p1.draw(g);
b.p2.draw(g);
g.setColor(Color.white);
g.drawString(""+b.p1Score,15,50);
g.drawString(""+b.p2Score,370,50);
repaint();
}
//event listining class
public class AL extends KeyAdapter { //key buildings
#Override
public void keyPressed(KeyEvent e) {
b.p1.keyPressed( e);
b.p2.keyPressed( e);
}
public void keyRealesed(KeyEvent e){
b.p1.keyReleased( e);
b.p2.keyReleased( e);
}
}
public static void main(String[] args) {
PingPong pp = new PingPong();
//create and start threads
Thread ball=new Thread(b);
ball.start();
Thread p1=new Thread(b.p1);
Thread p2= new Thread(b.p2);
p1.start();
p2.start();
}
}
this is my ball class:
package pingpong;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Rectangle;
import java.util.Random;
public class Ball implements Runnable{
//global variables
int x,y,XDir,YDir;
//score
int p1Score,p2Score;
Paddle p1=new Paddle(15 , 140, 1);
Paddle p2=new Paddle(370, 140 ,2 );
Rectangle ball;
public Ball(int x,int y){
p1Score=p2Score=0;
this.x=x;
this.y=y;
//randomly moving the ball
Random r=new Random();
int rDir = r.nextInt(1);
if (rDir == 0) {
rDir--;
}setXDir(rDir);
int yrDir = r.nextInt(1);
if (yrDir == 0) {
yrDir--;
}setYDir(yrDir);
//create 'ball'
ball = new Rectangle(this.x, this.y,7, 7);
}
public void collision(){
if(ball.intersects(p1.paddle)){
setXDir(+1);}
if(ball.intersects(p2.paddle)){
setXDir(-1);}
}
public void draw(Graphics g){
g.setColor(Color.cyan);
g.fillRect(ball.x,ball.y,ball.width,ball.height);
}
public void move(){
collision();
ball.x +=XDir;
ball.y +=YDir;
//bounce the ball when edge is detected
if(ball.x<0){
setXDir(+1);
//add to score
p1Score++; //?
}
if(ball.x>=385){
setXDir(-1);
//add to score
p2Score++; //?
}
if(ball.y<=15)
setYDir(+1);
if(ball.y>=270)
setYDir(-1);
}
public void setXDir(int xdir){
XDir=xdir;
}
public void setYDir(int ydir){
YDir=ydir;
}
public void run(){
try{
while(true){
move();
Thread.sleep(4);
}
}catch(Exception e) {System.out.println("sorry"+e.getMessage());}
}
}
and there is my paddle class :
package pingpong;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Rectangle;
import java.awt.event.KeyEvent;
public class Paddle implements Runnable {
int x, y, yDir, id;
Rectangle paddle;
public Paddle(int x, int y, int id) {
this.x = x;
this.y = y;
this.id = id;
paddle = new Rectangle(x, y, 15, 50);
}
public void keyPressed(KeyEvent e) {
switch (id) {
default:
System.out.println("please enter a valid id");
break;
case 1:
if (e.getKeyCode() == e.VK_UP) {
setYDir(-1);
}
if (e.getKeyCode() == e.VK_DOWN) {
setYDir(+1);
}
break;
case 2:
if (e.getKeyCode() == e.VK_W) {
setYDir(-1);
}
if (e.getKeyCode() == e.VK_S) {
setYDir(+1);
}
break;
}
}
public void keyReleased(KeyEvent e) {
switch (id) {
default:
System.out.println("please enter a valid id");
break;
case 1:
if (e.getKeyCode() == e.VK_UP) {
setYDir(0);
}
if (e.getKeyCode() == e.VK_DOWN) {
setYDir(0);
}
break;
case 2:
if (e.getKeyCode() == e.VK_W) {
setYDir(0);
}
if (e.getKeyCode() == e.VK_S) {
setYDir(0);
}
break;
}
}
public void draw(Graphics g) {
switch (id) {
default:
System.out.println("please enter a valid id");
break;
case 2:
g.setColor(Color.YELLOW);
//draw paddle #1
g.fillRect(paddle.x, paddle.y, paddle.width, paddle.height);
break;
case 1:
g.setColor(Color.white);
// draw paddle #2
g.fillRect(paddle.x, paddle.y, paddle.width, paddle.height);
break;
}
}
public void setYDir(int ydir) {
yDir = ydir;
}
public void move() {
paddle.x += yDir;
if (paddle.y <= 15) {
paddle.y = 15;
}
if (paddle.y >= 250) {
paddle.y = 250;
}
}
#Override
public void run() {
try {
while (true) {
move();
Thread.sleep(6);
}
} catch (Exception e) {
System.out.println("try again" + e.getMessage());
}
}
}
I personally think I have a problem in the paddle but I can't figure it out.

If you're moving your paddle in Y axis (inside move, this looks wrong:
paddle.x += yDir;
Should be
paddle.y += yDir;

Java image following my cursor

I'd like to make something similar to a cursor, ( I get no errors )
So basically I get the coordinates once I enter the applet, and based on them I have my image drawn.
Here's the code... Can you please tell me where I'm wrong ? Thanks
import java.applet.Applet;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.Point;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.io.IOException;
import java.net.URL;
import javax.imageio.ImageIO;
public class Z_applets extends Applet implements
KeyListener, MouseListener, MouseMotionListener {
int z = 100;
int t = 100;
// boolean gigel = true;
//----------------- Images
Image image;
//-----------------
//----------------- Mouse Coordinates
Point p = null;
int x;
int y;
//----------------------------------
Color color = Color.GREEN;
public void init() {
addKeyListener(this);
addMouseListener(this);
}
public void paint(Graphics g) {
setBackground(Color.BLACK);
g.setColor(color);
g.drawImage(image, x, y, this);
g.fillOval(z, t, 15, 15);
}
public void update(Graphics g) {
paint(g);
}
public void loadImage() {
//URL url = getClass().getResource("borat.jpg");
//image = getToolkit().getImage(url);
try {
URL url = new URL(getCodeBase(), "trollface.png");
System.out.println(getCodeBase());
image = ImageIO.read(url);
} catch (IOException e) {
System.out.println("error" + e.getMessage());
}
}
#Override
public void keyTyped(KeyEvent ke) {
}
#Override
public void keyPressed(KeyEvent ke) {
char option;
option = ke.getKeyChar();
switch (option) {
case 'w': {
t--;
repaint();
break;
}
case 's': {
t++;
repaint();
break;
}
case 'a': {
z--;
repaint();
break;
}
case 'd': {
z++;
repaint();
break;
}
case '1': {
color = Color.GREEN;
break;
}
case '2': {
color = Color.RED;
break;
}
case '3': {
color = Color.YELLOW;
break;
}
// case 'r':
// {
// loadImage();
// repaint();
// break;
// }
}
}
#Override
public void keyReleased(KeyEvent ke) {
}
#Override
public void mouseClicked(MouseEvent me) {
// p = me.getPoint();
// x = p.x;
// y = p.y;
// repaint();
}
#Override
public void mousePressed(MouseEvent me) {
}
#Override
public void mouseReleased(MouseEvent me) {
}
#Override
public void mouseEntered(MouseEvent me) {
// p=me.getPoint();
//-------Debug--------
System.out.println(p);
System.out.println(p.x);
System.out.println(p.y);
//----------------------
// x = p.x;
// y = p.y;
// repaint();
}
#Override
public void mouseExited(MouseEvent me) {
}
#Override
public void mouseDragged(MouseEvent me) {
}
#Override
public void mouseMoved(MouseEvent me) {
p = me.getPoint();
x = p.x;
y = p.y;
repaint();
}
}

Without knowing what problem you have exactly, I suppose the image isn't being moved.
I looks you don't register a MouseMotionListener so do that and implement the mouseMoved method.

eclipse applet blank screen

I'm trying to make a game in Eclipse that runs on Windows 8 using type keys.
Whenever I run the app using extends Applet I just get a blank screen. I can change the color of the background but none of my images are showing. I can even play with the app and use my arrow keys to get the returns but I can't see anything on the screen. I'm not sure if I should extend Applet or JApplet.
Here's my code
package kiloboltgame;
import java.applet.Applet;
import java.awt.*;
import java.awt.Color;
import java.awt.Frame;
import java.awt.Image;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.Graphics;
import java.net.URL;
public class StartingClass extends Applet implements Runnable, KeyListener {
private Robot robot;
private Image image, currentSprite, character, characterDown, characterJumped, background;
private Graphics second;
private URL base;
private static Background bg1, bg2;
#Override
public void init() {
setSize(800, 480);
setBackground(Color.BLACK);
setFocusable(true);
addKeyListener(this);
Frame frame = (Frame) this.getParent().getParent();
frame.setTitle("Q-Bot Alpha");
try {
base = getDocumentBase();
} catch (Exception e){
//TODO: handle exception
}
character = getImage(base, "data/character.png");
characterDown = getImage(base, "data/down.png");
characterJumped = getImage(base, "data/jumped.png");
currentSprite = character;
background = getImage(base, "data/background.png");
}
#Override
public void start() {
bg1 = new Background(0,0);
bg2 = new Background(2160, 0);
robot = new Robot();
Thread thread = new Thread(this);
thread.start();
}
#Override
public void stop() {
//super.stop();
}
#Override
public void destroy() {
//super.destroy();
}
#Override
public void run() {
while (true) {
robot.update();
if (robot.isJumped()){
currentSprite = characterJumped;
} else if (robot.isJumped() == false && robot.isDucked() == false){
currentSprite = character;
}
bg1.update();
bg2.update();
repaint();
try {
Thread.sleep(17);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
#Override
public void update(Graphics g){
if (image == null){
image = createImage(this.getWidth(), this.getHeight());
second = image.getGraphics();
}
second.setColor(getBackground());
second.fillRect(0, 0, getWidth(), getHeight());
second.setColor(getForeground());
paint(second);
g.drawImage(image, 0, 0, this);
}
#Override
public void paint(Graphics g){
g.drawImage(background, bg1.getBgX(), bg1.getBgY(), this);
g.drawImage(background, bg2.getBgX(), bg2.getBgY(), this);
g.drawImage(currentSprite, robot.getCenterX()-61, robot.getCenterY()-63, this);
}
#Override
public void keyPressed(KeyEvent e) {
switch (e.getKeyCode()) {
case KeyEvent.VK_UP:
System.out.println("Move Up");
break;
case KeyEvent.VK_DOWN:
currentSprite = characterDown;
if (robot.isJumped() == false){
robot.setDucked(true);
robot.setSpeedX(0);
}
break;
case KeyEvent.VK_LEFT:
robot.moveLeft();
robot.setMovingLeft(true);
break;
case KeyEvent.VK_RIGHT:
robot.moveRight();
robot.setMovingRight(true);
break;
case KeyEvent.VK_SPACE:
robot.jump();
break;
}
}
#Override
public void keyReleased(KeyEvent e) {
switch (e.getKeyCode()) {
case KeyEvent.VK_UP:
System.out.println("Stop moving up");
break;
case KeyEvent.VK_DOWN:
currentSprite = character;
break;
case KeyEvent.VK_LEFT:
robot.stopLeft();
break;
case KeyEvent.VK_RIGHT:
robot.stopRight();
break;
case KeyEvent.VK_SPACE:
//System.out.println("Stop jumping");
break;
}
}
#Override
public void keyTyped(KeyEvent arg0) {
// TODO Auto-generated method stub
}
public static Background getBg1(){
return bg1;
}
public static Background getBg2(){
return bg2;
}
}