Develop Reference

Java Game - Not Painting until After Thread.sleep

I'm currently coding a game and I'm trying to have it where if you click on the first button on the front page, it shows a transition screen for 5 seconds, and then shows the game. Here is my code:
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.image.BufferedImage;
import java.io.File;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class ForgottenMain extends JPanel implements KeyListener,MouseListener{
/**
*
*/
private static final int TIMER_DELAY = 35;
private static final long serialVersionUID = -4926251405849574401L;
public static BufferedImage attic,flashlight,player,killer,frontpage,transition;
public static boolean onFrontPage,up,down,left,right,inAttic,onTransition;
public static int px,py,kx,ky;
public static Thread th1,th2;
public static JFrame frame = new JFrame("Forgotten");
public static void main(String[] args){
onFrontPage = true;
px = 600;
py = 400;
ForgottenMain fm = new ForgottenMain();
frame.add(fm);
frame.setSize(1200,800);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLocationRelativeTo(null);
frame.setResizable(false);
frame.setVisible(true);
frame.add(new ForgottenMain());
fm.repaint();
}
public ForgottenMain(){
init();
}
public void init(){
setSize(1200,800);
setVisible(true);
frame.addKeyListener(this);
frame.addMouseListener(this);
try{
player = ImageIO.read(new File("char.png"));
flashlight = ImageIO.read(new File("flashlightimage.png"));
attic = ImageIO.read(new File("attic.png"));
killer = ImageIO.read(new File("killer.png"));
frontpage = ImageIO.read(new File("frontpageoutline.png"));
transition = ImageIO.read(new File("transitionoutline.png"));
} catch (Exception e){
e.printStackTrace();
}
// Gameloop
new javax.swing.Timer(TIMER_DELAY, new ActionListener() {
public void actionPerformed(ActionEvent e) {
gameLoop();
}
}).start();
}
#Override
public void paintComponent(Graphics g){
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
int fx = px - 1033;
int fy = py - 635;
kx = 500;
ky = 500;
// Removes the flickering of the images
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
// Resets the screen to make sure that it only shows the character once
g2.clearRect(0, 0, 1200, 800);
// Draws the background attic
if(inAttic == true){
System.out.println("Drawing attic");
g2.drawImage(attic,0,0,this);
}
if(onFrontPage == true){
g2.drawImage(frontpage, 0, 0, this);
}
// Draws the player
if(onFrontPage == false && onTransition == false){
g2.drawImage(player, px, py, this);
// Draws the Serial Killer
g2.drawImage(killer, kx, ky, this);
// Draws the flashlight
g2.drawImage(flashlight, fx, fy, this);
}
if(onTransition == true){
g2.drawImage(transition, 0, 0, this);
System.out.println("Drawing Transition");
try {
System.out.println("Sleeping for 5 Seconds");
Thread.sleep(5000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("Done sleeping.");
onTransition = false;
inAttic = true;
}
System.out.println(px + " " + py);
}
public void gameLoop(){
}
#Override
public void mouseClicked(MouseEvent arg0) {
System.out.println("MouseLocation: " + arg0.getX() + ", " + arg0.getY());
}
#Override
public void mouseEntered(MouseEvent arg0) {
}
#Override
public void mouseExited(MouseEvent arg0) {
}
#Override
public void mousePressed(MouseEvent e) {
if(e.getX() > 499 && e.getY() > 343 && e.getX() < 748 && e.getY() < 391){
onFrontPage = false;
onTransition = true;
repaint();
}
}
#Override
public void mouseReleased(MouseEvent arg0) {
}
My problem is, in the paint method, in the if statement testing if onTransition is equal to true, it's supposed to draw the image transition, wait 5 seconds, and then draw the game.
However, right now it's waiting 5 seconds, then quickly drawing the transition screen and then the game. For some reason they are out of order.
How can I fix this? I have tried alternate methods of waiting 5 seconds, for example using currentTimeMillis();, but have the same outcome.

You have some serious problems:
you add panels twice
you have some circuitous use of frame etc
Beyond that the following will work: you have to realize that you don't have control of the painting process. Therefore you should launch a new thread to count the sleep and let the paint do its work uninhibited.
(Also I have removed static - if you really want them you can try to put them back in - if it doesnt work you just throw them out)
class F extends JPanel implements MouseListener{
/**
*
*/
private static final int TIMER_DELAY = 35;
private static final long serialVersionUID = -4926251405849574401L;
public BufferedImage attic,flashlight,player,killer,frontpage,transition;
public boolean onFrontPage,up,down,left,right,inAttic,onTransition;
public int px,py,kx,ky;
public static Thread th1,th2;
public JFrame frame = new JFrame("Forgotten");
public F(){
init();
}
public void init(){
setSize(1200,800);
setVisible(true);
onFrontPage = true;
px = 600;
py = 400;
frame.add(this);
frame.setSize(1200,800);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLocationRelativeTo(null);
frame.setResizable(false);
frame.setVisible(true);
frame.addMouseListener(this);
try{
// player = ImageIO.read(new File("char.png"));
// flashlight = ImageIO.read(new File("flashlightimage.png"));
// attic = ImageIO.read(new File("attic.png"));
// killer = ImageIO.read(new File("killer.png"));
attic = ImageIO.read(new File(...));
frontpage = ImageIO.read(new File(...));
transition = ImageIO.read(new File(...));
} catch (Exception e){
e.printStackTrace();
}
}
#Override
public void paintComponent(Graphics g){
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
int fx = px - 1033;
int fy = py - 635;
kx = 500;
ky = 500;
// Removes the flickering of the images
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
// Resets the screen to make sure that it only shows the character once
g2.clearRect(0, 0, 1200, 800);
// Draws the background attic
if(inAttic == true){
System.out.println("Drawing attic"+System.currentTimeMillis());
g2.drawImage(attic,0,0,this);
}
if(onFrontPage == true){
g2.drawImage(frontpage, 0, 0, this);
}
// Draws the player
if(onFrontPage == false && onTransition == false){
g2.drawImage(player, px, py, this);
// Draws the Serial Killer
g2.drawImage(killer, kx, ky, this);
// Draws the flashlight
g2.drawImage(flashlight, fx, fy, this);
}
if(onTransition == true){
Graphics gt=transition.getGraphics();
gt.setColor(Color.red);
gt.drawString("xxx"+System.currentTimeMillis(), 10, 100);
g2.drawImage(transition, 0, 0, this);
onTransition = false;
inAttic = true;
}
System.out.println(px + " " + py);
}
public void gameLoop(){
}
#Override
public void mouseClicked(MouseEvent arg0) {
System.out.println("MouseLocation: " + arg0.getX() + ", " + arg0.getY());
}
#Override
public void mouseEntered(MouseEvent arg0) {
}
#Override
public void mouseExited(MouseEvent arg0) {
}
#Override
public void mousePressed(MouseEvent e) {
onFrontPage = false;
onTransition = true;
Thread th=new Thread() {
public void run() {
repaint();
System.out.println("Drawing Transition"+System.currentTimeMillis());
try {
System.out.println("Sleeping for 5 Seconds"+System.currentTimeMillis());
Thread.sleep(5000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("Done sleeping."+System.currentTimeMillis());
repaint();
}
};
th.start();
}
#Override
public void mouseReleased(MouseEvent arg0) {
}
}

Call paintComponent method

I am trying to paint a line when my variable readyToDraw is TRUE by using an if... statement in class's Paint method paintComponent() . I guess I'm doing something wrong because the line never gets painted. How do I fix this? Is there a way to call paintComponent() from another method?
Full code:
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.Rectangle2D;
import java.awt.Graphics2D;
import java.util.Iterator;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JButton;
import javax.swing.SwingWorker;
import javax.swing.border.LineBorder;
import javax.swing.AbstractAction;
import javax.swing.Action;
public class MainFrame {
public int x1, x2, y1, y2;
private boolean readyToDraw = false;
private int clickCount = 0;
private JFrame frame;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
MainFrame window = new MainFrame();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the application.
*/
public MainFrame() {
initialize();
}
/**
* Initialize the contents of the frame.
*/
private void initialize() {
frame = new JFrame();
frame.setBounds(100, 100, 800, 600);
frame.setResizable(false);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().setLayout(null);
JPanel buttonPanel = new JPanel();
buttonPanel.setBackground(Color.WHITE);
buttonPanel.setBorder(new LineBorder(new Color(0, 0, 0), 2, true));
buttonPanel.setBounds(10, 11, 100, 85);
frame.getContentPane().add(buttonPanel);
buttonPanel.setLayout(null);
JPanel paint = new Paint();
frame.getContentPane().add(paint);
JButton btnLine = new JButton("Line");
btnLine.setBackground(Color.LIGHT_GRAY);
btnLine.setBounds(4, 4, 92, 25);
btnLine.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
// Execute when button is pressed
if (readyToDraw == true) {
System.out.println("Let's draw!");
}
else {
}
System.out.println("Line");
}
});
JButton btnRectangle = new JButton("Rectangle");
btnRectangle.setBackground(Color.LIGHT_GRAY);
btnRectangle.setBounds(4, 30, 92, 25);
btnRectangle.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
// Execute when button is pressed
if (readyToDraw == true) {
System.out.println("Let's draw!");
}
else {
}
System.out.println("Rectangle");
}
});
JButton btnCircle = new JButton("Circle");
btnCircle.setBackground(Color.LIGHT_GRAY);
btnCircle.setBounds(4, 56, 92, 25);
btnCircle.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
// Execute when button is pressed
if (readyToDraw == true) {
System.out.println("Let's draw!");
}
else {
}
System.out.println("Circle");
}
});
buttonPanel.add(btnLine);
buttonPanel.add(btnRectangle);
buttonPanel.add(btnCircle);
}
private class Paint extends JPanel implements MouseListener {
public Paint() {
this.setBackground(Color.WHITE);
this.setBounds(120, 11, 664, 550);
this.addMouseListener(this);
}
#Override
public void paintComponent(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
super.paintComponent(g);
//if (readyToDraw) {
g2.setStroke(new BasicStroke(4));
g2.setColor(Color.BLACK);
g2.drawLine(x1, y1, x2, y2);
//}
}
#Override
public void mouseEntered(MouseEvent arg0) {
Toolkit toolkit = Toolkit.getDefaultToolkit();
Image image = toolkit.getImage("cursor.png");
Point hotSpot = new Point(15, 15);
Cursor cursor = toolkit.createCustomCursor(image, hotSpot, "Dot");
this.setCursor(cursor);
}
#Override
public void mouseExited(MouseEvent arg0) {
Cursor dotCursor = new Cursor(Cursor.DEFAULT_CURSOR);
this.setCursor(dotCursor);
}
public void mouseClicked(MouseEvent e) {
int x1 = 0;
int y1 = 0;
int x2 = 0;
int y2 = 0;
if (clickCount == 0) {
x1 = e.getX();
y1 = e.getY();
clickCount++;
} else if (clickCount == 1) {
x2 = e.getX();
y2 = e.getY();
clickCount++;
readyToDraw = true;
} else {
clickCount = 0;
readyToDraw = false;
repaint();
}
System.out.println(x1 + " " + y1 + " " + clickCount + " " + x2
+ " " + y2 + readyToDraw);
}
public void mousePressed(MouseEvent arg0) {
// TODO Auto-generated method stub
}
public void mouseReleased(MouseEvent arg0) {
// TODO Auto-generated method stub
}
}
}

Java: white frames while painting canvas

public class Screen extends Canvas implements Runnable {
private static final int MAX_FPS = 60;
private static final int FPS_SAMPLE_SIZE = 6;
private boolean[] keysPressed = new boolean[256];
private ArrayList<Character> characters = new ArrayList<>();
private ArrayList<Character> ai = new ArrayList<>();
private Thread thread;
private BufferedImage bg;
//for testing putposes
private Player slime = new Player("Slime.png", 100, 100);
private Player bird = new Player("Bird.png", 250, 250);
private Player giant = new Player("Giant.png", 250, 500);
private Player swordsman = new Player("Swordsman.png", 500, 250);
//screen dimensions
private int height = ((Toolkit.getDefaultToolkit().getScreenSize().height-32)/5*4);
private int width = Toolkit.getDefaultToolkit().getScreenSize().width;
private long prevTick = -1;
private LinkedList<Long> frames = new LinkedList<>();
private int averageFPS;
private boolean running;
public Screen() {
setSize(width, height);
try {bg = ImageIO.read(new File("GUI Images/success.jpg"));}
catch (Exception e) {Utilities.showErrorMessage(this, e);}
characters.add(slime);
// ai.add(bird);
//ai.add(giant);
// ai.add(swordsman);
addKeyListener(new KeyListener() {
public void keyPressed(KeyEvent e) {keysPressed[e.getKeyCode()] = true;}
public void keyReleased(KeyEvent e) {keysPressed[e.getKeyCode()] = false;}
public void keyTyped(KeyEvent e) {}
});
addMouseListener(new MouseListener() {
public void mouseClicked(MouseEvent e) {}
public void mouseEntered(MouseEvent e) {}
public void mouseExited(MouseEvent e) {}
public void mousePressed(MouseEvent e) {}
public void mouseReleased(MouseEvent e) {}
});
addMouseMotionListener(new MouseMotionListener() {
public void mouseDragged(MouseEvent e) {}
public void mouseMoved(MouseEvent e) {}
});
addMouseWheelListener(new MouseWheelListener() {
public void mouseWheelMoved(MouseWheelEvent e) {}
});
setVisible(true);
start();
}
public void paint(Graphics g){
BufferStrategy bs = getBufferStrategy();
if(getBufferStrategy() == null){
createBufferStrategy(3);
return;
}
g = bs.getDrawGraphics();
g.drawImage(bg,0,0,width,height, null);
g.drawString(String.valueOf(averageFPS), 0, 0);
for (Character character : ai){
character.setY(character.getY() + (int)(Math.random() * 10 - 5));
character.setX(character.getX() + (int)(Math.random() * 10 - 5));
}
for (Character character : ai) {g.drawImage(character.getImage(), character.getX(), character.getY(), null);}
for (Character character : characters) {g.drawImage(character.getImage(), character.getX(), character.getY(), null);}
g.dispose();
bs.show();
}
public void run() {
while (running) {
tick();
repaint();
}
}
public synchronized void start() {
running = true;
thread = new Thread(this);
thread.start();
}
public synchronized void stop() {
try {thread.join();}
catch (InterruptedException e) {Utilities.showErrorMessage(this, e);}
}
public void tick() {
if (keysPressed[KeyEvent.VK_W] && (slime.getY() > 0)) {slime.setY(slime.getY() - 1);}
if (keysPressed[KeyEvent.VK_S] && (slime.getY() < height)) {slime.setY(slime.getY() + 1);}
if (keysPressed[KeyEvent.VK_A] && (slime.getY() > 0)) {slime.setX(slime.getX() - 1);}
if (keysPressed[KeyEvent.VK_D] && (slime.getY() < width)) {slime.setX(slime.getX() + 1);}
// System.out.println(slime.getX() + ", " + slime.getY());
long pastTime = System.currentTimeMillis() - prevTick;
prevTick = System.currentTimeMillis();
if (frames.size() == FPS_SAMPLE_SIZE) {
frames.remove();
}
frames.add(pastTime);
// Calculate average FPS
long sum = 0;
for (long frame : frames) {
sum += frame;
}
long averageFrame = sum / FPS_SAMPLE_SIZE;
averageFPS = (int)(1000 / averageFrame);
// Only if the time passed since the previous tick is less than one
// second divided by the number of maximum FPS allowed do we delay
// ourselves to give Time time to catch up to our rendering.
if (pastTime < 1000.0 / MAX_FPS) {
try {
Thread.sleep((1000 / MAX_FPS) - pastTime);
System.out.println(averageFPS);
} catch (InterruptedException e) {
System.out.println(e);
}
}
}
}
There's my code, essentially this is just test code for the screen to see if I can properly paint objects to the screen, but there's erratic white frames that keep getting painted. They don't seem to be caused by any sort of input in particular, they just happen seemingly randomly during frame refreshes. Any ideas as to what it might be?

Don't override paint and use a BufferStrategy within it. Painting is usually done on a need to do bases (AKA "passive" rendering). BufferStrategy is a "active" rendering approach, where you take control of the paint process and update the buffer directly, the two don't tend to play well together
Take the logic from the current paint method and place it within your game loop.
This will require you to remove your call to start within the constructor, as the component won't have been added to a valid native peer (a component which is displayed on the screen).
Instead, create an instance of Screen, add it to your frame and then call start, for example...
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.FontMetrics;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Toolkit;
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.awt.event.MouseWheelEvent;
import java.awt.event.MouseWheelListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.image.BufferStrategy;
import java.awt.image.BufferedImage;
import java.io.File;
import java.util.ArrayList;
import java.util.LinkedList;
import javax.imageio.ImageIO;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class TestScreen {
public static void main(String[] args) {
new TestScreen();
}
public TestScreen() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
Frame frame = new Frame("Testing");
frame.addWindowListener(new WindowAdapter() {
#Override
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
Screen screen = new Screen();
frame.add(screen);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
screen.start();
}
});
}
public class TestPane extends JPanel {
public TestPane() {
}
#Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
g2d.dispose();
}
}
public class Screen extends Canvas implements Runnable {
private static final int MAX_FPS = 60;
private static final int FPS_SAMPLE_SIZE = 6;
private boolean[] keysPressed = new boolean[256];
private ArrayList<Character> characters = new ArrayList<>();
private ArrayList<Character> ai = new ArrayList<>();
private Thread thread;
private BufferedImage bg;
private long prevTick = -1;
private LinkedList<Long> frames = new LinkedList<>();
private int averageFPS;
private boolean running;
public Screen() {
try {
bg = ImageIO.read(new File("GUI Images/success.jpg"));
} catch (Exception e) {
e.printStackTrace();
}
addKeyListener(new KeyListener() {
public void keyPressed(KeyEvent e) {
keysPressed[e.getKeyCode()] = true;
}
public void keyReleased(KeyEvent e) {
keysPressed[e.getKeyCode()] = false;
}
public void keyTyped(KeyEvent e) {
}
});
addMouseListener(new MouseListener() {
public void mouseClicked(MouseEvent e) {
}
public void mouseEntered(MouseEvent e) {
}
public void mouseExited(MouseEvent e) {
}
public void mousePressed(MouseEvent e) {
}
public void mouseReleased(MouseEvent e) {
}
});
addMouseMotionListener(new MouseMotionListener() {
public void mouseDragged(MouseEvent e) {
}
public void mouseMoved(MouseEvent e) {
}
});
addMouseWheelListener(new MouseWheelListener() {
public void mouseWheelMoved(MouseWheelEvent e) {
}
});
}
#Override
public Dimension getPreferredSize() {
int height = ((Toolkit.getDefaultToolkit().getScreenSize().height - 32) / 5 * 4);
int width = Toolkit.getDefaultToolkit().getScreenSize().width;
return new Dimension(width, height);
}
public void run() {
createBufferStrategy(3);
BufferStrategy bs = null;
while (running) {
bs = getBufferStrategy();
Graphics g = bs.getDrawGraphics();
g.drawImage(bg, 0, 0, getWidth(), getHeight(), null);
FontMetrics fm = g.getFontMetrics();
g.setColor(Color.RED);
g.drawString(String.valueOf(averageFPS), 0, fm.getAscent());
g.dispose();
bs.show();
tick();
}
}
public synchronized void start() {
running = true;
thread = new Thread(this);
thread.start();
}
public synchronized void stop() {
try {
thread.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
public void tick() {
// if (keysPressed[KeyEvent.VK_W] && (slime.getY() > 0)) {
// slime.setY(slime.getY() - 1);
// }
// if (keysPressed[KeyEvent.VK_S] && (slime.getY() < height)) {
// slime.setY(slime.getY() + 1);
// }
// if (keysPressed[KeyEvent.VK_A] && (slime.getY() > 0)) {
// slime.setX(slime.getX() - 1);
// }
// if (keysPressed[KeyEvent.VK_D] && (slime.getY() < width)) {
// slime.setX(slime.getX() + 1);
// }
// // System.out.println(slime.getX() + ", " + slime.getY());
long pastTime = System.currentTimeMillis() - prevTick;
prevTick = System.currentTimeMillis();
if (frames.size() == FPS_SAMPLE_SIZE) {
frames.remove();
}
frames.add(pastTime);
// Calculate average FPS
long sum = 0;
for (long frame : frames) {
sum += frame;
}
long averageFrame = sum / FPS_SAMPLE_SIZE;
averageFPS = (int) (1000 / averageFrame);
// Only if the time passed since the previous tick is less than one
// second divided by the number of maximum FPS allowed do we delay
// ourselves to give Time time to catch up to our rendering.
if (pastTime < 1000.0 / MAX_FPS) {
try {
Thread.sleep((1000 / MAX_FPS) - pastTime);
System.out.println(averageFPS);
} catch (InterruptedException e) {
System.out.println(e);
}
}
}
}
}

Mouse pressed and released in java applet

My code below is for a checkers program. If the user either clicks on a stop button or holds the mouse, it stops, and the go button or mouse release moves the checkers from the beginning.
I am not able to figure out how to move the checkers from the same position that they were stopped at. Help Please!
import java.awt.Button;
import java.awt.Graphics;
import java.awt.Color;
import java.awt.Image;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
public class Checkers extends java.applet.Applet implements Runnable,
ActionListener {
Thread runner;
int xpos;
Image offscreenImg;
Graphics offscreenG;
Button goButton, stopButton, exitButton;
private ExitButtonHandler ebHandler;
public void init() {
// offscreenImg = createImage(getWidth(), getHeight());
offscreenImg = createImage(this.size().width, this.size().height);
offscreenG = offscreenImg.getGraphics();
setSize(200, 250);
addMouseListener(new Mouse());
goButton = new Button("Go");
goButton.setBounds(10, 200, 90, 20);
setLayout(null);
stopButton = new Button("Stop");
stopButton.setBounds(100, 200, 90, 20);
setLayout(null);
exitButton = new Button("Exit");
ebHandler = new ExitButtonHandler();
exitButton.addActionListener(ebHandler);
exitButton.setBounds(55, 220, 90, 20);
setLayout(null);
add(goButton);
add(stopButton);
add(exitButton);
stopButton.addActionListener(this);
goButton.addActionListener(this);
}
public void start() {
if (runner == null) {
runner = new Thread(this);
runner.start();
}
}
public void stop() {
if (runner != null) {
runner.stop();
runner = null;
}
}
public void run() {
while (true) {
for (xpos = 5; xpos <= 105; xpos += 4) {
repaint();
try {
Thread.sleep(100);
} catch (InterruptedException e) {
}
}
xpos = 5;
for (xpos = 105; xpos >= 5; xpos -= 4) {
repaint();
try {
Thread.sleep(100);
} catch (InterruptedException e) {
}
}
xpos = 5;
}
}
public void update(Graphics g) {
paint(g);
}
public void paint(Graphics g) {
// Draw background onto the buffer area
offscreenG.setColor(Color.blue);
offscreenG.fillRect(0, 0, 100, 100);
offscreenG.setColor(Color.red);
offscreenG.fillRect(0, 100, 100, 100);
offscreenG.setColor(Color.red);
offscreenG.fillRect(100, 0, 100, 100);
offscreenG.setColor(Color.blue);
offscreenG.fillRect(100, 100, 100, 100);
// Draw checker
offscreenG.setColor(Color.green);
offscreenG.fillOval(xpos, 5, 90, 90);
offscreenG.setColor(Color.yellow);
offscreenG.fillOval(-xpos + 110, 105, 90, 90);
// Now, transfer the entire buffer onto the screen
g.drawImage(offscreenImg, 0, 0, this);
}
public void destroy() {
offscreenG.dispose();
}
// Mouse events
public class Mouse extends MouseAdapter {
public void mousePressed(MouseEvent e) {
stop();
}
public void mouseReleased(MouseEvent e) {
start();
}
}
// Button events
public void actionPerformed(ActionEvent e) {
if (e.getSource() == stopButton) {
stop();
} else if (e.getSource() == goButton) {
start();
}
}
// exit button
public class ExitButtonHandler implements ActionListener {
public void actionPerformed(ActionEvent e) {
System.exit(0);
}
}
}

You are recreating a new Thread which starts from the beginning every time you call the start function. Also, after you call stop you will not be able to "resume" where you left off.
You will want to change your Thread to use a flag of some type (boolean stopped;) and then change that flag when you call stop and start, so the Thread doesn't actually end but just "pauses." (stops moving, but is actually still running)
if (stopped) {
//dont do stuff
}
else {
//do stuff
}

How do i use KeyListener in java?

How do I use KeyListener on this code to move up and down? Ii know how to use KeyListener but I don't know where it put it on this code.
import java.awt.*;
import java.awt.image.*;
import java.awt.event.*;
import java.awt.geom.*;
import javax.swing.*;
public class ControlPanel extends JPanel implements Runnable,ActionListener,KeyListener,MouseListener{
private MainPanel main;
private final static int maxWidth = 800, maxHeight = 600; //width & height of JPanel
private boolean running; //keeps track of state of the program
private Thread thread;
private Graphics2D graphics;
private Image image; //used for double buffering
private BufferedImage bgImage;
private String s = "";
Font f = new Font("Times New Roman",Font.PLAIN,50);
Timer t = new Timer(2000,this);
private int typed = 0;
private int x = 50,y = 500;
public ControlPanel(MainPanel main) {
this.setDoubleBuffered(false); //we'll use our own double buffering method
this.setBackground(Color.black);
this.setPreferredSize(new Dimension(maxWidth, maxHeight));
this.setFocusable(true);
this.requestFocus();
this.main = main;
addKeyListener(this);
addMouseListener(this);
t.start();
}
public static void main(String[] args) {
new MainPanel();
}
public void addNotify() {
super.addNotify();
startGame();
}
public void stopGame() {
running = false;
}
//Creates a thread and starts it
public void startGame() {
if (thread == null || !running) {
thread = new Thread(this);
}
thread.start(); //calls run()
}
public void run() {
running = true;
init();
while (running) {
createImage(); //creates image for double buffering
///////////////USE THESE 2 METHODS////////////////////
update(); //use this to change coordinates, update values, etc
draw(); //use this to draw to the screen
//////////////////////////////////////////////////////
drawImage(); //draws on the JPanel
}
System.exit(0);
}
//Use this to create or initialize any variables or objects you have
public void init() {
}
public void initGame(){
}
//Use this to update anything you need to update
public void update() {
}
//Use this to draw anything you need to draw
public void draw() {
graphics.setColor(Color.WHITE);
graphics.fillRect(250, 450, 300,100);
graphics.setColor(Color.WHITE);
graphics.fillRect(250, 320, 300,100);
graphics.setColor(Color.GREEN);
graphics.setFont(f);
graphics.drawString(s, x, y);
typed = 0;
graphics.setFont(f);
graphics.setColor(Color.blue);
graphics.drawString("HANGMAN", 270,75);
graphics.setFont(f);
graphics.setColor(Color.blue);
graphics.drawString("PLAY", 330, 390);
graphics.setFont(f);
graphics.setColor(Color.blue);
graphics.drawString("QUIT", 330, 520);
graphics.setColor(Color.red);
graphics.drawRect(248, 318, 304,104);
}
//creates an image for double buffering
public void createImage() {
if (image == null) {
image = createImage(maxWidth, maxHeight);
if (image == null) {
System.out.println("Cannot create buffer");
return;
}
else
graphics = (Graphics2D)image.getGraphics(); //get graphics object from Image
}
if (bgImage == null) {
graphics.setColor(Color.black);
graphics.fillRect(0, 0, maxWidth, maxHeight);
//System.out.println("No background image");
}
else {
//draws a background image on the Image
graphics.drawImage(bgImage, 0, 0, null);
}
}
//outputs everything to the JPanel
public void drawImage() {
Graphics g;
try {
g = this.getGraphics(); //a new image is created for each frame, this gets the graphics for that image so we can draw on it
if (g != null && image != null) {
g.drawImage(image, 0, 0, null);
g.dispose(); //not associated with swing, so we have to free memory ourselves (not done by the JVM)
}
image = null;
}catch(Exception e) {System.out.println("Graphics objects error");}
}
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
}
public void keyPressed(KeyEvent e) {
}
public void keyReleased(KeyEvent e) {
}
public void keyTyped(KeyEvent e) {
typed = 1;
s+=Character.toString(e.getKeyChar());
s+=" ";
System.out.println(s);
}
#Override
public void mouseClicked(MouseEvent e) {
System.out.println(e.getPoint());
}
#Override
public void mouseEntered(MouseEvent arg0) {
// TODO Auto-generated method stub
}
#Override
public void mouseExited(MouseEvent arg0) {
// TODO Auto-generated method stub
}
#Override
public void mousePressed(MouseEvent arg0) {
// TODO Auto-generated method stub
}
#Override
public void mouseReleased(MouseEvent arg0) {
// TODO Auto-generated method stub
}
}

KeyListener isn‘t designated for listening of keyboard events for Swing JComponents, use KeyBindings instead, output to the Swing GUI should be from Swing Action

You have added key listener by calling this      
addKeyListener(this);