i made simple game by java , it’s about “tennis background” and “tennis ball” , and the ball is randomally move automatically ,
my game consist of two file , 1st file fore Jpanel , and 2nd file for JFrame ,
my question is : i need to control of “stopping and resuming” the ball by clicking the mouse , i tried to put wait() during thread running loop , but it’s faild , i don’t know what is the reason ! , so please review my code and then tell me what is the wrong , and what is the true method of “pause&resume” thread in my simple game !
tennis.java file (which contain the thread):
/*
* tennis.java
*
* Created on Nov 15, 2011, 3:35:28 PM
*/
package io;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
public class tennis extends javax.swing.JPanel implements Runnable{
BufferedImage ball;
BufferedImage bg;
int ball_h = 0;
int ball_w = 0;
int height = 0;
int width = 0;
int yPos = -1;
int xPos = 10;
int pause = 20;
// Move Speed
int xMov = 5;
int yMov = 10;
boolean clicked = false;
int play = 0;
Thread runner;
/** Creates new form tennis */
public tennis() throws IOException {
ball = ImageIO.read(new File("tennis/ball.png"));
bg = ImageIO.read(new File("tennis/bg.jpg"));
ball_h = 50;
ball_w = 50;
height = 600 - ball_h;
width = 800 - ball_w;
runner = new Thread(this);
runner.start();
}
public void start(){
if(play == 0){
play = 1;
clicked = true;
}else{
play = 0;
clicked = true;
}
System.out.println(play);
}
public void stop(){
runner = null;
}
@Override
public void paint(Graphics g){
Graphics2D g2D = (Graphics2D) g;
g2D.drawImage(bg, 0, 0, 800,600, this);
g2D.drawImage(ball, xPos, yPos,50,50, this);
}
/** This method is called from within the constructor to
* initialize the form.
* WARNING: Do NOT modify this code. The content of this method is
* always regenerated by the Form Editor.
*/
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(this);
this.setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 400, Short.MAX_VALUE)
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 300, Short.MAX_VALUE)
);
}// </editor-fold>
// Variables declaration - do not modify
// End of variables declaration
@Override
public void run() {
while(runner == runner){
if(xPos >= (width))
{
xMov *= -1;
}
xPos += xMov;
if(xPos < 1)
{
xMov *= -1;
}
if(yPos >= (height-ball_h))
{
yMov *= -1 ;
}
yPos += yMov;
if(yPos < 1)
{
yMov *= -1 ;
}
repaint();
try {
if(play == 1){
Thread.sleep(pause);
}else{
synchronized(this){
while(play == 0){
wait();
}
}
}
} catch (InterruptedException ex) {
Logger.getLogger(tennis.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
}
Tennis3D.java file(frame for starting the game and define the thread) :
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
/*
* Tennis3D.java
*
* Created on Nov 15, 2011, 3:42:42 PM
*/
package io;
import io.tennis;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
public class Tennis3D extends javax.swing.JFrame implements MouseListener{
tennis tennis;
/** Creates new form Tennis3D */
public Tennis3D() {
super("Tennis3D");
setSize(800,600);
try {
tennis = new tennis();
add(tennis);
tennis.addMouseListener(this);
} catch (IOException ex) {
Logger.getLogger(Tennis3D.class.getName()).log(Level.SEVERE, null, ex);
}
setVisible(true);
}
/** This method is called from within the constructor to
* initialize the form.
* WARNING: Do NOT modify this code. The content of this method is
* always regenerated by the Form Editor.
*/
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 400, Short.MAX_VALUE)
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 300, Short.MAX_VALUE)
);
pack();
}// </editor-fold>
/**
* @param args the command line arguments
*/
public static void main(String args[]) {
Tennis3D tennis = new Tennis3D();
}
// Variables declaration - do not modify
// End of variables declaration
@Override
public void mouseClicked(MouseEvent e) {
tennis.start();
}
@Override
public void mousePressed(MouseEvent e) {
}
@Override
public void mouseReleased(MouseEvent e) {
}
@Override
public void mouseEntered(MouseEvent e) {
}
@Override
public void mouseExited(MouseEvent e) {
}
}
Thank you for your help 🙂
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Answer
This is piggy-backing on what Nerdtron wrote in the comment above. Typically a game loop looks like this
while (!game.isOver())
{
if (!game.isPaused())
game.update() // this moves your ball, players, etc
}