Develop Reference

Eclipse Game Lags Too Much

I am making a game and tutorials for how to make it on youtube. Here is the link to the channel. I explain the first part of what I have and why I have it because I know that is helpful for filling you in.
Link to part 1(Then watch the rest of parts. #Chris, this is helpful for solving the problem so don't flag the post).
https://www.youtube.com/watch?v=IRn_ZGhJZ94
I noticed as I was testing out my code for part 4. before recording, the game lagged HORRIBLY. I have alot of code, and any help is appreciated.
Game class:
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import javax.swing.ImageIcon;
import javax.swing.JPanel;
import javax.swing.Timer;
#SuppressWarnings("serial")
public class Game extends JPanel implements ActionListener{
Timer mainTimer;
Paddle paddle;
Ball ball;
int blockCount = 16;
static ArrayList<Block> blocks = new ArrayList<Block>();
public Game() {
setFocusable(true);
paddle = new Paddle(250, 300);
addKeyListener(new KeyAdapt(paddle));
ball = new Ball(275, 280);
mainTimer = new Timer(10, this);
mainTimer.start();
}
public void paint(Graphics g) {
super.paint(g);
Graphics2D g2d = (Graphics2D) g;
ImageIcon ic = new ImageIcon("C:/Users/Elliot/Desktop/Eclipse Game/background.png");
g2d.drawImage(ic.getImage(), 0, 0, null);
paddle.draw(g2d);
ball.draw(g2d);
for(int i = 0; i < blockCount; i++) {
Block b = blocks.get(i);
b.draw(g2d);
}
}
#Override
public void actionPerformed(ActionEvent arg0) {
paddle.update();
ball.update();
for(int i = 0; i < blocks.size(); i++) {
Block b = blocks.get(i);
b.update();
}
repaint();
startGame();
}
public void addBlock(Block b) {
blocks.add(b);
}
public static void removeBlock(Block b) {
blocks.remove(b);
}
public static ArrayList<Block> getBlockList() {
return blocks;
}
public void startGame() {
for(int i = 0; i < blockCount; i++) {
addBlock(new Block(i*60 + 7, 20));
addBlock(new Block(i*60 + 7, 0));
}
}
}
Main class(The frame part):
import javax.swing.JFrame;
public class Main {
public static void main(String[] args) {
JFrame frame = new JFrame("Game");
frame.setSize(500, 400);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new Game());
frame.setResizable(false);
frame.setVisible(true);
}
}
Key Adapt class:
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
public class KeyAdapt extends KeyAdapter{
Paddle p;
public KeyAdapt(Paddle paddle) {
p = paddle;
}
public void keyPressed(KeyEvent e) {
p.keyPressed(e);
}
public void keyReleased(KeyEvent e) {
p.keyReleased(e);
}
}
Paddle class:
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Rectangle;
import java.awt.event.KeyEvent;
import javax.swing.ImageIcon;
public class Paddle {
int velX;
int speed = 3;
static int x1, y1;
public Paddle(int x1, int y1) {
this.x1 = x1;
this.y1 = y1;
}
public void update() {
x1+=velX;
checkCollisions();
}
public void draw(Graphics2D g2d) {
g2d.drawImage(getPaddleImg(), x1, y1, null);
}
public static Image getPaddleImg() {
ImageIcon ic = new ImageIcon("C:/Users/Elliot/Desktop/Eclipse Game/paddle.png");
return ic.getImage();
}
public void keyPressed(KeyEvent e) {
int key = e.getKeyCode();
if(key==KeyEvent.VK_D) {
velX = speed;
} else if(key==KeyEvent.VK_A){
velX = -speed;
}
}
public void keyReleased(KeyEvent e) {
int key = e.getKeyCode();
if(key==KeyEvent.VK_D) {
velX = 0;
} else if(key==KeyEvent.VK_A){
velX = 0;
}
}
public void checkCollisions() {
if(getBounds().getX() + getBounds().getWidth() >= 500) {
x1 = 440;
} else if(getBounds().getX() <= 0) {
x1 = 0;
}
}
public static Rectangle getBounds() {
return new Rectangle(x1, y1 - 1, getPaddleImg().getWidth(null), getPaddleImg().getHeight(null));
}
}
Ball class:
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Rectangle;
import javax.swing.ImageIcon;
import javax.swing.JOptionPane;
public class Ball {
int velX;
int velY;
int speed = 3;
int x, y;
public Ball(int x, int y) {
this.x = x;
this.y = y;
}
public void update() {
x+=velX;
y+=velY;
checkCollisions();
}
public void draw(Graphics2D g2d) {
g2d.drawImage(getBallImg(), x, y, null);
}
public Image getBallImg() {
ImageIcon ic = new ImageIcon("C:/Users/Elliot/Desktop/Eclipse Game/ball.png");
return ic.getImage();
}
public void checkCollisions() {
for(int i = 0; i < Game.getBlockList().size(); i++) {
Block b = Game.getBlockList().get(i);
if(getBounds().intersects(b.getBounds()) && velX!=-speed) {
velY=speed;
velX =- speed;
Game.removeBlock(b);
}
else if(getBounds().intersects(b.getBounds())) {
velY=speed;
velX = speed;
Game.removeBlock(b);
}
}
if(getBounds().intersects(Paddle.getBounds())) {
velY = -speed;
} else if (getBounds().getY() <= 0 && velX!=speed) {
velY = speed;
velX =- speed;
}else if (getBounds().getY() <= 0 && velX!=-speed) {
velY = speed;
velX = speed;
} else if(getBounds().getY() >= 400) {
JOptionPane.showMessageDialog(null, "You Lost! :( ");
System.exit(0);
}
if(getBounds().getX() <= 0) {
velX = speed;
} else if(getBounds().getX() >= 500 - getBounds().getWidth()) {
velX = -speed;
}
}
public Rectangle getBounds() {
return new Rectangle(x, y, getBallImg().getWidth(null), getBallImg().getHeight(null));
}
}
Block class:
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Rectangle;
import javax.swing.ImageIcon;
public class Block {
int x2, y2;
public Block(int x2, int y2) {
this.x2 = x2;
this.y2 = y2;
}
public void update() {
}
public void draw(Graphics2D g2d){
g2d.drawImage(getBlockImg(), x2, y2, null);
}
public static Image getBlockImg() {
ImageIcon ic = new ImageIcon("C:/Users/Elliot/Desktop/Eclipse Game/block.png");
return ic.getImage();
}
public Rectangle getBounds() {
return new Rectangle(x2, y2, getBlockImg().getWidth(null), getBlockImg().getHeight(null));
}
}
I also have a folder called Eclipse Game on my desktop and I refer to it in my code.
Again, I understand this is alot but any idea with making it lag less is helpful. Also, watching the tutorial (look at the beginning for the link) on making what I have finished so far will help make it less confusing for you to understand how the code works. The game seriously lags so much I cannot play.

There are multiple issues.
The first, as I already mentioned in my comment, is that you're calling startGame() inside your timer action listener:
#Override
public void actionPerformed(ActionEvent arg0) {
paddle.update();
ball.update();
for(int i = 0; i < blocks.size(); i++) {
Block b = blocks.get(i);
b.update();
}
repaint();
startGame();
}
This is adding 3,200 blocks every second to the game, so you don't want that. I think the simplest place to put startGame() is at the end of the game constructor:
public Game() {
setFocusable(true);
paddle = new Paddle(250, 300);
addKeyListener(new KeyAdapt(paddle));
ball = new Ball(275, 280);
mainTimer = new Timer(10, this);
mainTimer.start();
startGame();
}
The other really big problem is that you're constantly reloading the images all the time. For example, look at this snippet:
if(getBounds().intersects(b.getBounds()) && velX!=-speed) {
velY=speed;
velX =- speed;
Game.removeBlock(b);
}
else if(getBounds().intersects(b.getBounds())) {
velY=speed;
velX = speed;
Game.removeBlock(b);
}
That is 4 calls to getBounds(), and if we take a look at that:
return new Rectangle(x2, y2, getBlockImg().getWidth(null), getBlockImg().getHeight(null));
You are loading 2 images which in total is 4*2*blockCount images every 10ms, just for this one method. Instead of loading images all the time, do something like this:
class GameResources {
static Image ballImage;
static Image paddleImage;
static Image blockImage;
// call GameResources.loadResources() at the
// beginning of main() or something
static void loadResources() {
// load all 3 images once here and be done
ballImage = ...;
paddleImage = ...;
blockImage = ...;
}
Then finally, you have an issue with removing items from the list while iterating over it, Ball.checkCollisions:
for(int i = 0; i < Game.getBlockList().size(); i++) {
Block b = Game.getBlockList().get(i);
if(getBounds().intersects(b.getBounds()) && velX!=-speed) {
velY=speed;
velX =- speed;
// removeBlock changes blocks.size()
Game.removeBlock(b);
}
else if(getBounds().intersects(b.getBounds())) {
velY=speed;
velX = speed;
// removeBlock changes blocks.size()
Game.removeBlock(b);
}
}
Instead you need to do something like this:
Iterator<Block> iter = Game.getBlockList().iterator();
while (it.hasNext()) {
Block b = it.next();
if(getBounds().intersects(b.getBounds()) && velX!=-speed) {
velY=speed;
velX =- speed;
// safely removing
it.remove();
}
else if(getBounds().intersects(b.getBounds())) {
velY=speed;
velX = speed;
// safely removing
it.remove();
}
}
And another possible boundary issue in Game.paint:
// using blockCount after possibly
// removing items from the list
// vvvvvvvvvv
for(int i = 0; i < blockCount; i++) {
Block b = blocks.get(i);
b.draw(g2d);
}
For simple iterations like this, you should use for-each:
for(Block b : blocks) {
b.draw(g2d);
}
After all of that the game runs pretty smoothly, except for some type of issue with the key listener which I didn't have time to figure out. I might look at it again after dinner.
edit:
I noticed a lot of other small things, so here is the program fixed up a bit more with my comments.
Some of the classes aren't public anymore just because I had them all in one source file.
import javax.swing.SwingUtilities;
import javax.swing.Timer;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JOptionPane;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyAdapter;
import java.util.ArrayList;
import java.util.Iterator;
import java.awt.Rectangle;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Dimension;
import java.net.URL;
import javax.imageio.ImageIO;
import java.io.IOException;
import java.io.File;
public class BlockGame {
public static void main(String[] args) {
// Swing program should always begin on the Swing
// thread with a call to invokeLater.
// See https://docs.oracle.com/javase/tutorial/uiswing/concurrency/initial.html
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
try {
// change this to
// .loadImages();
GameResources.loadInternetImages();
} catch (IOException x) {
x.printStackTrace();
return;
}
JFrame frame = new JFrame("Game");
// frame.setSize(500, 400);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// frame.add(new Game());
// Instead of calling setSize on the JFrame
// directly, set a preferred size on the game
// panel, then call pack() on the JFrame
Game game = new Game();
game.setPreferredSize(new Dimension(500, 400));
frame.add(game);
frame.pack();
frame.setResizable(false);
frame.setVisible(true);
// I started the game here instead
// of in the game loop, so the panel
// is visible and stuff beforehand.
game.startGame();
}
});
}
}
class Game extends JPanel implements ActionListener {
Timer mainTimer;
Paddle paddle;
Ball ball;
// I removed this because it's only ever
// used by startGame.
// int blockCount = 16;
// I changed this to an instance variable
// (not static) and passed the game in to
// update so the game objects can access
// it.
ArrayList<Block> blocks = new ArrayList<Block>();
public Game() {
setFocusable(true);
paddle = new Paddle(250, 300);
addKeyListener(new KeyAdapt(paddle));
ball = new Ball(275, 280);
mainTimer = new Timer(10, this);
// I moved this to the startGame() method
// mainTimer.start();
}
// Swing programs should override paintComponent
// instead of paint.
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
// You should create a copy instead of
// directly using the graphics object which
// the component uses.
// This is so any changes you make to it
// don't affect the Swing paint routines.
Graphics2D g2d = (Graphics2D) g.create();
// ImageIcon ic = new ImageIcon("C:/Users/Elliot/Desktop/Eclipse Game/background.png");
// g2d.drawImage(ic.getImage(), 0, 0, null);
// Painting static resource.
g2d.drawImage(GameResources.backgroundImage, 0, 0, null);
paddle.draw(g2d);
ball.draw(g2d);
// This loop will throw an out of bounds
// exception once the first block is removed.
// vvvvvvvvvv
// for(int i = 0; i < blockCount; i++) {
// Block b = blocks.get(i);
// b.draw(g2d);
// }
// using for each
for (Block b : blocks) {
b.draw(g2d);
}
// Dispose the copied graphics when you're done.
g2d.dispose();
}
#Override
public void actionPerformed(ActionEvent arg0) {
paddle.update(this);
ball.update(this);
// for(int i = 0; i < blocks.size(); i++) {
// Block b = blocks.get(i);
// b.update();
// }
for (Block b : blocks) {
b.update(this);
}
repaint();
// I moved this to main
// startGame();
}
public void addBlock(Block b) {
blocks.add(b);
}
public void removeBlock(Block b) {
blocks.remove(b);
}
public ArrayList<Block> getBlockList() {
return blocks;
}
// I added this method so that the
// ball can access the paddle without
// static variables.
public Paddle getPaddle() {
return paddle;
}
public void startGame() {
// So the method won't be called twice
// and put the game in some unexpected
// state.
if (mainTimer.isRunning()) {
throw new IllegalStateException("game already started");
}
int initialBlockCount = 16;
for(int i = 0; i < initialBlockCount; i++) {
addBlock(new Block(i*60 + 7, 20));
addBlock(new Block(i*60 + 7, 0));
}
mainTimer.start();
}
}
// Generally speaking you should use
// Swing key bindings now, instead of
// key listeners.
//
// Key listeners have problems with
// the focus system: Swing components
// only send out key events when they
// have the focus.
//
// Key bindings don't have this issue.
//
// You can set up key bindings so they
// trigger any time the key is pressed
// in the focused window.
//
// https://docs.oracle.com/javase/tutorial/uiswing/misc/keybinding.html
//
class KeyAdapt extends KeyAdapter {
Paddle p;
public KeyAdapt(Paddle paddle) {
p = paddle;
}
public void keyPressed(KeyEvent e) {
p.keyPressed(e);
}
public void keyReleased(KeyEvent e) {
p.keyReleased(e);
}
}
class Paddle {
int velX;
int speed = 3;
// I changed these from static
// to instance variables.
int x1, y1;
// I added these variables to
// help with the key listener
// logic.
boolean leftPressed, rightPressed;
public Paddle(int x1, int y1) {
this.x1 = x1;
this.y1 = y1;
}
public void update(Game game) {
x1 += velX;
checkCollisions();
}
public void draw(Graphics2D g2d) {
g2d.drawImage(GameResources.paddleImage, x1, y1, null);
}
// public static Image getPaddleImg() {
// ImageIcon ic = new ImageIcon("C:/Users/Elliot/Desktop/Eclipse Game/paddle.png");
// return ic.getImage();
// }
public void keyPressed(KeyEvent e) {
int key = e.getKeyCode();
// This logic is a little more robust
// because it handles cases where both
// keys are being held at the same time.
// Also see computeVelX().
if (key == KeyEvent.VK_D) {
leftPressed = true;
// velX = speed;
} else if (key == KeyEvent.VK_A) {
rightPressed = true;
// velX = -speed;
}
computeVelX();
}
public void keyReleased(KeyEvent e) {
int key = e.getKeyCode();
// This logic is a little more robust
// because it handles cases where both
// keys are being held at the same time.
// Also see computeVelX().
if (key == KeyEvent.VK_D) {
leftPressed = false;
// velX = 0;
} else if (key == KeyEvent.VK_A) {
rightPressed = false;
// velX = 0;
}
computeVelX();
}
public void computeVelX() {
// This way the keys will never
// "stick". If both keys are
// held at the same time, velX
// is just 0 until one of the
// keys is released.
velX = 0;
if (leftPressed) {
velX += speed;
}
if (rightPressed) {
velX -= speed;
}
}
public void checkCollisions() {
// I used a variable instead of calling
// getBounds() repeatedly.
Rectangle bounds = getBounds();
if (bounds.getX() + bounds.getWidth() >= 500) {
x1 = 440;
} else if (bounds.getX() <= 0) {
x1 = 0;
}
}
// I change this from static to an instance method.
public Rectangle getBounds() {
// return new Rectangle(x1, y1 - 1, getPaddleImg().getWidth(null), getPaddleImg().getHeight(null));
int width = GameResources.paddleImage.getWidth(null);
int height = GameResources.paddleImage.getHeight(null);
return new Rectangle(x1, y1 - 1, width, height);
}
}
class Ball {
int velX;
int velY;
int speed = 3;
int x, y;
public Ball(int x, int y) {
this.x = x;
this.y = y;
}
public void update(Game game) {
x += velX;
y += velY;
checkCollisions(game);
}
public void draw(Graphics2D g2d) {
// g2d.drawImage(getBallImg(), x, y, null);
g2d.drawImage(GameResources.ballImage, x, y, null);
}
// public Image getBallImg() {
// ImageIcon ic = new ImageIcon("C:/Users/Elliot/Desktop/Eclipse Game/ball.png");
// return ic.getImage();
// }
public void checkCollisions(Game game) {
// Using an iterator instead of looping with size()
// directly, because we want to remove items from
// the list while iterating.
// The problem with removing while iterating with
// size() is that once you remove an element, the
// list shifts all the other elements back by 1,
// so on the next iteration of the loop you end
// up skipping an item.
// (Say you remove the element at index 5. Then
// all the elements shift back, so that e.g. the
// element at index 6 is now at index 5. The variable
// i is incremented, so you end up skipping the element
// that was at index 6 before the removal.
Iterator<Block> iter = game.getBlockList().iterator();
Rectangle bounds = getBounds();
while (iter.hasNext()) {
Block b = iter.next();
Rectangle bBounds = b.getBounds();
if (bounds.intersects(bBounds) && velX != -speed) {
velY = speed;
velX =- speed;
// Game.removeBlock(b);
iter.remove();
} else if (bounds.intersects(bBounds)) {
velY = speed;
velX = speed;
// Game.removeBlock(b);
iter.remove();
}
}
//
Rectangle pBounds = game.getPaddle().getBounds();
if (bounds.intersects(pBounds)) {
velY = -speed;
} else if (bounds.getY() <= 0 && velX != speed) {
velY = speed;
velX =- speed;
} else if (bounds.getY() <= 0 && velX != -speed) {
velY = speed;
velX = speed;
} else if (bounds.getY() >= 400) {
JOptionPane.showMessageDialog(null, "You Lost! :( ");
System.exit(0);
}
if (bounds.getX() <= 0) {
velX = speed;
} else if(bounds.getX() >= 500 - bounds.getWidth()) {
velX = -speed;
}
}
public Rectangle getBounds() {
// return new Rectangle(x, y, getBallImg().getWidth(null), getBallImg().getHeight(null));
int width = GameResources.ballImage.getWidth(null);
int height = GameResources.ballImage.getHeight(null);
return new Rectangle(x, y, width, height);
}
}
class Block {
int x2, y2;
public Block(int x2, int y2) {
this.x2 = x2;
this.y2 = y2;
}
public void update(Game game) {
}
public void draw(Graphics2D g2d){
// g2d.drawImage(getBlockImg(), x2, y2, null);
g2d.drawImage(GameResources.blockImage, x2, y2, null);
}
// public static Image getBlockImg() {
// ImageIcon ic = new ImageIcon("C:/Users/Elliot/Desktop/Eclipse Game/block.png");
// return ic.getImage();
// }
public Rectangle getBounds() {
// return new Rectangle(x2, y2, getBlockImg().getWidth(null), getBlockImg().getHeight(null));
int width = GameResources.blockImage.getWidth(null);
int height = GameResources.blockImage.getHeight(null);
return new Rectangle(x2, y2, width, height);
}
}
class GameResources {
public static Image backgroundImage;
public static Image blockImage;
public static Image ballImage;
public static Image paddleImage;
public static void loadImages() throws IOException {
// Load images once here.
// I didn't test this method since I don't have the images, but it
// should work. ImageIO.read will give better error messages than
// using ImageIcon. ImageIcon.getImage() will just return null if
// there was a problem, which doesn't tell you what the problem
// actually was.
paddleImage =
ImageIO.read(new File("C:/Users/Elliot/Desktop/Eclipse Game/paddle.png"));
ballImage =
ImageIO.read(new File("C:/Users/Elliot/Desktop/Eclipse Game/ball.png"));
blockImage =
ImageIO.read(new File("C:/Users/Elliot/Desktop/Eclipse Game/block.png"));
backgroundImage =
ImageIO.read(new File("C:/Users/Elliot/Desktop/Eclipse Game/background.png"));
}
public static void loadInternetImages() throws IOException {
// These images are from
// http://stackoverflow.com/questions/19209650/example-images-for-code-and-mark-up-qas
paddleImage =
ImageIO.read(new URL("http://i.stack.imgur.com/gYxHm.png"));
ballImage =
ImageIO.read(new URL("http://i.stack.imgur.com/gJmeJ.png"));
blockImage =
ImageIO.read(new URL("http://i.stack.imgur.com/F0JHK.png"));
backgroundImage =
ImageIO.read(new URL("http://i.stack.imgur.com/P59NF.png"));
}
}

Java: Problems with KeyListener in a Space Invaders game

I'm trying to implement a KeyListener in a Space Invaders game in Java to move the ship (by now, it's just a red rectangle).
I think it's fine implemented, but i can't make it works.
Here is the ship's one:
import java.awt.Color;
import java.awt.Graphics;
public class Nave{
int x, y;
int AnchoNave = 40, AltoNave = 40; // WIDTH_SHIP and HIGH_SHIP
Finestra f; // WINDOW
int velocidad = 4, v = 0; // VELOCITY
Joc j;
Nave(Finestra f, int x, int y){
this.f = f;
this.x = x;
this.y = y;
}
void pintaNave(Graphics g){
g.setColor(Color.RED);
g.drawRect(x, y, AnchoNave, AltoNave);
g.setColor(Color.RED);
g.fillRect(x, y, AnchoNave, AltoNave);
}
void movimiento(){ // this is not in the loop now.
x+=velocidad;
if (x>f.AMPLE-AnchoNave-10){
x=0;
}
}
}
Here is the Window's one:
import java.awt.Color;
import java.awt.Component;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.event.*;
import javax.swing.JFrame;
public class Finestra extends JFrame implements ActionListener, KeyListener{
Image im;
Graphics g;
int AMPLE=600,ALT=500; // WIDTH and HIGH
Joc j;
Nave nave; // Nave = SHIP
int velocidad = 10; // VELOCITY
public static void main(String[] args) {
new Finestra(); // Finestra = WINDOW
}
Finestra(){
super("-+- Space Invaders -+-");
setVisible(true);
setSize(AMPLE,ALT);
im=this.createImage(AMPLE, ALT);
g=im.getGraphics();
j=new Joc(this);
j.playing();
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setResizable(false);
addKeyListener(this);
setFocusable(true);
setFocusTraversalKeysEnabled(false);
}
public void update(Graphics g) {
paint(g);
}
public void paint(Graphics g) {
g.drawImage(im, 0,0, null);
}
#Override
public void actionPerformed(ActionEvent e) {
j.nave.x =j.nave.x + j.nave.v;
repaint();
}
#Override
public void keyPressed(KeyEvent e) {
int tecla = e.getKeyCode();
if (tecla == KeyEvent.VK_RIGHT)
j.nave.v = +10;
if (tecla == KeyEvent.VK_LEFT)
j.nave.v = -10;
}
#Override
public void keyReleased(KeyEvent e) {
j.nave.v = 0;
}
#Override
public void keyTyped(KeyEvent e) {}
}
And finally this is the class that contains the loop of the game:
import java.awt.Color;
import java.awt.Graphics;
public class Joc{
Finestra f; // WINDOW
Enemigos c1[]; // ENEMIES
Nave nave; // SHIP
Joc(Finestra f){ // JOC = GAME
this.f=f;
}
void playing() {
initicalitzaJoc();
do {
moviments(); // MOVEMENTS
detectaColisions(); // COLLISION DETECTION
pintarPantalla(f.g); // PAINT SCREEN
f.repaint();
try {
Thread.sleep(20);
} catch (InterruptedException e) {
e.printStackTrace();
}
}while(true);
}
private void detectaColisions() {
}
private void moviments() {
for(int i=0;i<c1.length;i++)
c1[i].movimiento();
}
private void initicalitzaJoc() {
c1 = new Enemigos[15]; // ENEMIES
for (int i=0; i<5; i++)
c1[i] = new Enemigos(f, 100+i*80, 100, 5);
for (int i=5; i<10; i++)
c1[i] = new Enemigos(f, 100+(i-5)*80, 150, 5);
for (int i=10; i<15; i++)
c1[i] = new Enemigos(f, 100+(i-10)*80, 200, 5);
// Nave del jugador: // PLAYER'S SHIP
nave = new Nave(f,300-40/2, 500-40-5);
}
void pintarPantalla(Graphics g) {
g.setColor(Color.WHITE);
g.fillRect(0, 0, 600,500);
for (int i=0; i<5; i++)
c1[i].pinta(g,1);;
for (int i=5; i<10; i++)
c1[i].pinta(g,3);
for (int i=10; i<15; i++)
c1[i].pinta(g,6);
nave.pintaNave(g);
}
}
I don't know where the mistake could be, maybe in the loop... i don't know.
The question is how can i fixed it to can move the ship using the keyboard?
This Space Invaders is a homework, I'm obliged to use the KeyListener... How can I make it works ?

I'have found the answer.
The problem was that the class "Finestra" ejecute the function "playing" (so the loop starts) before reading the keys.
It's enough chasing the order:
Finestra(){
super("-+- Space Invaders -+-");
setVisible(true);
setSize(AMPLE,ALT);
im=this.createImage(AMPLE, ALT);
g=im.getGraphics();
j=new Joc(this);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setResizable(false);
addKeyListener(this);
setFocusable(true);
setFocusTraversalKeysEnabled(false);
System.out.println("hola");
j.playing(); // enter the loop after reading the keys.
}

Looking at your key event handler:
#Override
public void keyPressed(KeyEvent e) {
int tecla = e.getKeyCode();
if (tecla == KeyEvent.VK_RIGHT)
j.nave.v = +10;
if (tecla == KeyEvent.VK_LEFT)
j.nave.v = -10;
}
It changes a variable called 'v' on your ship (nave).
Then your movimiento (presumably 'move') method on your ship uses another variable, velocidad. It completely ignores v!
Delete the variable v and just use velocidad.
Also, you only ever call movimiento on your enemy ships, never on your player's ship! So naturally, it never moves.

Eclipse vs BlueJ issue

I tried this code in BlueJ which should create a rectangle and move it around but it does not function. Then I put the same exact code into Eclipse and it functions as I thought it would. Any ideas to why this works in Eclipse but not in BlueJ?
import javax.swing.*;
import java.awt.*;
public class Shapes
{
public static void main(String[] args)
{
JFrame frame = new JFrame("Test");
Draw object = new Draw();
frame.add(object);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(400,400);
frame.setVisible(true);
}
}
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class Draw extends JPanel implements ActionListener, KeyListener
{
Timer tm = new Timer(5,this);
int x = 0, y = 0, velX = 0, velY = 0;
public Draw()
{
tm.start();
addKeyListener(this);
setFocusable(true);
setFocusTraversalKeysEnabled(false);
}
public void paintComponent(Graphics g)
{
super.paintComponent(g);
g.setColor(Color.BLUE);
g.fillRect(x,y,100,20);
}
public void actionPerformed(ActionEvent e)
{
x += velX;
y += velY;
repaint();
}
public void keyPressed(KeyEvent e)
{
int c = e.getKeyCode();
if(c == KeyEvent.VK_LEFT)
{
velX = -1;
velY = 0;
}
if(c == KeyEvent.VK_UP)
{
velX = 0;
velY = 1;
}
if(c == KeyEvent.VK_RIGHT)
{
velX = 1;
velY = 0;
}
if(c == KeyEvent.VK_DOWN)
{
velX = 0;
velY = -1;
}
}
public void keyTyped(KeyEvent e){}
public void keyReleased(KeyEvent e)
{
velX = 0;
velY = 0;
}
}

I can see what you mean I believe it attaches it to that corner of the screen because when I resize the screen it moves with that corner. I think its not that BlueJ can't Run it properly i believe it can but it does it differently than what eclipse does.
I believe this question asks the same thing and it gets pretty good answers you should look at it first.

JPanel creates twice

I am trying to make a GUI for a battleship game. One class is for creating the GUI itself and a second class is on top of it to manage the board in the game. My problem is that the JPanel creates twice once a mouse click happens (the mouse click is supposed to be where one is firing in the game and then marks that as a hit/miss). I'm not sure why it is creating twice. Is it because of the passing of a panel? Code below and a photo of what the code generates.
import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import javax.swing.BorderFactory;
import javax.swing.JApplet;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JPanel;
public class BattleshipApplet extends JApplet implements MouseListener {
private final JButton playButton = new JButton("Play");
private final JLabel msgBar = new JLabel("Click Play to start game");
private BoardPanel panel;
public BattleshipApplet(){
playButton.addActionListener(this::playButtonClicked);
addMouseListener(this);
}
public void init(){
configureGui();
}
private void configureGui(){
setLayout(new BorderLayout());
JPanel buttons = new JPanel(new FlowLayout(FlowLayout.LEFT));
buttons.setBorder(BorderFactory.createEmptyBorder(0,5,0,0));
buttons.add(playButton);
add(buttons, BorderLayout.NORTH);
msgBar.setBorder(BorderFactory.createEmptyBorder(10,10,5,5));
add(createBoardPanel(), BorderLayout.CENTER);
add(msgBar, BorderLayout.SOUTH);
}
private BoardPanel createBoardPanel(){
panel = new BoardPanel();
return panel;
}
private void displayMessage(String msg){
msgBar.setText(msg);
}
private void playButtonClicked(ActionEvent event){
displayMessage("Play button clicked!");
}
public void mouseClicked(MouseEvent e) {
panel.mouseClickedAt(e.getX(), e.getY());
e.consume();
}
public void mouseEntered(MouseEvent e) {
}
public void mouseExited(MouseEvent e) {
}
public void mousePressed(MouseEvent e) {
}
public void mouseReleased(MouseEvent e) {
}
}
The board class using JPanel
[![import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JPanel;
public class BoardPanel extends JPanel {
int mx, my;
boolean rect1Clicked;
//gamePlay a;
public void init(){
rect1Clicked = false;
}
/***Your applet shall show the status of the board before and after
each shot, including the number of shots made and the status of
each place (no shot or hit/miss shot). ***/
public void paint(Graphics g){
boolean miss = false;
for (int i=0; i<11; i++){
g.setColor(Color.blue);
g.drawLine(20,20+i*28, 300, 20+i*28);
}
for (int i=0; i<11; i++)
g.drawLine(20+i*28,20,20+i*28,300);
//if inside board
if(rect1Clicked == true){
g.setColor(Color.green);
//aligns to square to check in computer board for hit/miss
int bx =(my-20)/28;
int by =(mx-20)/28;
//check hit on board
//if shot was a miss
if(miss == true ){
//update to white
g.setColor(Color.white);
}
//if shot was a hit
if(miss == false){
//update to red
g.setColor(Color.red);
}
//compare to line for fill
int fillx = mx/2;
int filly = my/2 ;
if(mx<=47){
fillx = 20;
}
if(mx>47 && mx<=75){
fillx = 48;
}
if(mx>75 && mx<=103){
fillx = 76;
}
if(mx>103 && mx <=131){
fillx = 104;
}
if(mx>131 && mx<=159){
fillx = 132;
}
if(mx>159 && mx<=187){
fillx = 160;
}
if(mx>187 && mx <=215){
fillx = 188;
}
if(mx>215 && mx <=243){
fillx = 216;
}
if(mx>243 && mx <=271){
fillx = 244;
}
if(mx>271 && mx<=299){
fillx = 272;
}
if(mx>299){
fillx = 300;
}
//y comparisons
if(my<=47){
filly = 20;
}
if(my>47 && my<=75){
filly = 48;
}
if(my>75 && my<=103){
filly = 76;
}
if(my>103 && my <=131){
filly = 104;
}
if(my>131 && my<=159){
filly = 132;
}
if(my>159 && my<=187){
filly = 160;
}
if(my>187 && my <=215){
filly = 188;
}
if(my>215 && my <=243){
filly = 216;
}
if(my>243 && my <=271){
filly = 244;
}
if(my>271 && my<=299){
filly = 272;
}
if(my>299){
filly = 300;
}
g.drawString("("+mx+","+my+")",mx,my);
//25 describes size of square
g.fillOval(fillx, filly, 25, 25);
}
}
public void game(BoardPanel p){
//while game plays
}
public void mouseClickedAt(int x, int y){
mx = x;
my = y;
//user clicked inside of board space
if(mx>20 && mx<300 && my>20 && my<300){
//send to board in MainBattleship
rect1Clicked = true;
}
//updates board
repaint();
}
}][1]][1]
I am so lost, thank you for any help!

Suggestions:
Don't override a JPanel's paint method but rather its paintComponent method as this is safer, and later when you want to do animation, will result in smoother animation.
Most important you almost always need to call the super's painting method within your own, else the JPanel will not remove previous image artifacts that need to be cleaned up. So if you continue to override paint (although I recommend against, this) the first line of your override should be super.paint(g);, or if you override paintComponent then the first line should be super.paintComponent(g);, of course assuming that you're methods use a Graphics parameter named g.
Also, add the MouseListener to the JPanel, not to the applet, since it is the mouse click location on the panel that matters to you.
Also, use a grid of components or some math to greatly simplify your code -- that ugly list of if blocks should be replaced by a much simpler for loop, one using basic math.
Consider extracting that logic discussed in the point above out of your painting method and into a model of some kind, perhaps a 2D array of boolean.
You're using a lot of "magic" numbers in your code, numbers that should be changed to a combination of constants and mathematically derived numbers.
Notice what happens if you click on your GUI, and then resize it, or if you minimize and then restore it -- you lose all red circles except for the last one pressed. This is another reason to use a grid of boolean or other model to hold state of the game, and then use this model when drawing your GUI.
On further thinking, you might want a 2D array of an enum or an int array, since the grid cell state will likely be more than 2 values (true or false), but rather will be three values -- untested, hit, and miss, and you'll likely want to fill your oval with red if a hit or white if a miss.
For example:
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.*;
import javax.swing.*;
public class GridExample {
private static void createAndShowGui() {
final GridPanel gridPanel = new GridPanel();
JButton resetBtn = new JButton(new AbstractAction("Reset") {
#Override
public void actionPerformed(ActionEvent e) {
gridPanel.reset();
}
});
JPanel btnPanel = new JPanel();
btnPanel.add(resetBtn);
JFrame frame = new JFrame("GridExample");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(gridPanel);
frame.getContentPane().add(btnPanel, BorderLayout.PAGE_END);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
#SuppressWarnings("serial")
class GridPanel extends JPanel {
private static final int ROWS = 10;
private static final int CELL_WIDTH = 28;
private static final int PAD = 20;
private static final int PREF_W = ROWS * CELL_WIDTH + 2 * PAD;
private static final int PREF_H = PREF_W;
private static final Color GRID_COLOR = Color.blue;
private static final Color CIRCLE_COLOR = Color.red;
private static final int SML_GAP = 2;
private boolean[][] grid = new boolean[ROWS][ROWS];
public GridPanel() {
addMouseListener(new MyMouse());
}
#Override
public Dimension getPreferredSize() {
if (isPreferredSizeSet()) {
return super.getPreferredSize();
}
return new Dimension(PREF_W, PREF_H);
}
public void reset() {
grid = new boolean[ROWS][ROWS]; // fills grid with false
repaint();
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D)g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
// draw grid:
g2.setColor(GRID_COLOR);
for (int i = 0; i <= ROWS; i++) {
int x1 = PAD + i * CELL_WIDTH;
int y1 = PAD;
int x2 = x1;
int y2 = PAD + CELL_WIDTH * ROWS;
g2.drawLine(x1, y1, x2, y2);
g2.drawLine(y1, x1, y2, x2);
}
// iterate through the grid boolean array
// draw red circles if the grid value is true.
g2.setColor(CIRCLE_COLOR);
int w = CELL_WIDTH - 2 * SML_GAP; // width of the circle to draw
int h = w;
// nested for loop to go through the grid array
for (int r = 0; r < grid.length; r++) {
for (int c = 0; c < grid[r].length; c++) {
if (grid[r][c]) {
int x = PAD + c * CELL_WIDTH + SML_GAP;
int y = PAD + r * CELL_WIDTH + SML_GAP;
g2.fillOval(x, y, w, h);
}
}
}
}
private class MyMouse extends MouseAdapter {
public void mousePressed(MouseEvent e) {
int x = e.getPoint().x;
int y = e.getPoint().y;
if (x < PAD || y < PAD) {
// clicked above or to right of grid
return;
}
int r = (y - PAD) / CELL_WIDTH;
int c = (x - PAD) / CELL_WIDTH;
// if clicked to right or below grid.
// the < 0 part is likely unnecessary, but why not be extra safe?
if (r >= ROWS || c >= ROWS || r < 0 || c < 0) {
return;
}
grid[r][c] = true;
repaint();
}
}
}

how can i use an array to make random circles

I have been working on a school assignment and the teacher wants us to make 7 circles appear on a JPanel and move downwards. Once a circle reaches the bottom a new circle should be made to replace the circle that reached the bottom of the JPanel. I decided to use an array to continue to make random circles but I cant get it to work right. I used a for loop to populate the array with circles that have a random radius and color. The code compiles but when I run it I get an exception. I am having a hard time getting the array to work properly. The other thing that I am not sure about is how to draw the circles so that they are space out across the JPanel.
The Code
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.util.Random;
public class keyExample extends JPanel implements ActionListener, KeyListener {
private Circle[] circles = new Circle[7];
Timer t = new Timer(5, this);
//current x and y
double x = 150, y = 200;
double changeX = 0, changeY = 0;
private Circle;
private int circlex = 0, circley = 0; // makes initial starting point of circles 0
private javax.swing.Timer timer2;
public keyExample() {
t.start();
addKeyListener(this);
setFocusable(true);
setFocusTraversalKeysEnabled(false);
}
timer2 = new javax.swing.Timer(33, new MoveListener());
timer2.start();
}
public void NewCircle() {
Random colors = new Random();
Color color = new Color(colors.nextInt(256), colors.nextInt(256), colors.nextInt(256));
Random num = new Random();
int radius = num.nextInt(45);
for (int i = 0; i < circles.length; i++) {
circles[i] = new Circle(circlex, circley, radius, color);
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.setColor(Color.BLUE);
g2.fill(new Rectangle2D.Double(x, y, 40, 40));
NewCircle();
for (int i = 0; i < circles.length; i++)
circles[i].fill(g);
}
public void actionPerformed(ActionEvent e) {
repaint();
x += changeX;
y += changeY;
changeX = 0;
changeY = 0;
}
public void up() {
if (y != 0) {
changeY = -3.5;
changeX = 0;
}
}
public void down() {
if (y <= 350) {
changeY = 3.5;
changeX = 0;
}
}
public void left() {
if (x >= 0) {
changeX = -3.5;
changeY = 0;
}
}
public void right() {
if (x <= 550) {
changeX = 3.5;
changeY = 0;
}
}
private class MoveListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
repaint();
Random speed = new Random();
int s = speed.nextInt(8);
circle.move(0, s);
}
}
public void keyPressed(KeyEvent e) {
int code = e.getKeyCode();
if (code == KeyEvent.VK_UP) {
up();
}
if (code == KeyEvent.VK_DOWN) {
down();
}
if (code == KeyEvent.VK_RIGHT) {
right();
}
if (code == KeyEvent.VK_LEFT) {
left();
}
}
public void keyTyped(KeyEvent e) {
}
public void keyReleased(KeyEvent e) {
}
}

Your problem is that you're trying to paint with the circle variable, a variable that you never assign a valid reference to.
One solution is to give it a valid reference via circle = new Circle(...), but having said that, I'll tell you to ignore it since you shouldn't even be using the variable circle. Just get rid of it. What you want to do is to use your circles array -- that's what you should be painting in your paintComponent method. Use a for loop inside of paintComponent and iterate through the array painting each circle item that the array holds.