Thread: Problem with Animation and Button Action

Hello all,

I'm new to this forum and to Java programming as well.

I've been trying to write down a code that run a simple animation of a ball on the screen (code is added below).

The ball itself wanders around the screen in one of four random directions (North-East, North-West, South-East, South-West) until it hits one of the panel borders or button #1 is pressed and then it changes direction.

The animation itself works fine: when no user input is involved (just a loop) the ball wanders around and changes direction whenever it changes direction. However, the button action does not.

Instead of changing the ball's direction, as it supposed to behave, clicking the button causes the program to freeze and not responding until the ball disappears & reappears in its new location with no animation on the way. Much as there is no-pause between the animation steps and the "repaint()" method having no effect. All there is a big delay after the button is pressed, and the ball changes it's location, rather than moving.

What I would like the program to do is to have the button to change the course of the ball, and while the button is not pressed - the ball keeps wandering the panel independently until it reaches the next border or the button is pressed again.

I know the program is pretty much crude, but right now I would like to cause it to work first and than temper with it.
You can see that some lines in the code have nothing to do with what I try to achieve, while other can use a more elegant substitutions. I've all entered Println's here and there to try and find where the problem is - yet no success.

I understand this is pretty much a long explanation, but I want to make my idea crystal clear for anyone who tries to help me. If you have any further questions - I will gladly answer.

Yoav.

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.Dimension;
import java.applet.AudioClip;
import java.io.*;
import java.net.*;
import java.awt.event.ItemListener;
import java.awt.event.ItemEvent;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.FlowLayout;
import java.applet.*;
import sun.audio.*;
import java.util.ArrayList;

public class go9 extends JFrame {
JTextArea displayArea;
JTextField typingArea;
static JPanel panel;
static Grp G1;
JFrame frame;
JButton button1;
JButton button2;
public static void main (String[] args) {
go9 gui = new go9();
gui.start();
}

public void start() {
frame = new JFrame();
G1= new Grp();
frame.repaint();
panel=new JPanel (new GridLayout(1,2));

button1 = new JButton("Buttons #1");
button1.addActionListener(new B1Listener());
button2 = new JButton("Button #2");
button2.addActionListener(new B2Listener());
panel.add(button1);
panel.add(button2);

frame.getContentPane().add(G1, BorderLayout.CENTER);
frame.getContentPane().add(panel, BorderLayout.PAGE_END);

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOS E);
frame.setSize(400,400);
frame.setVisible(true);
// for (int i=0; i<10; i++) {G1.run();}


}

class B1Listener implements ActionListener {
public void actionPerformed (ActionEvent e) {G1.run();}
}
class B2Listener implements ActionListener {
public void actionPerformed (ActionEvent e) {System.out.println(e.getID());}
}
}

class Grp extends JPanel {
static int x=100;
static int y=100;
int rand;
void run() {
if (x==0 || x==getWidth() || y==0 || y==getHeight()) {
if (x==0) {
rand=(int)((Math.random())*2);
System.out.println(rand);
if (rand==0) {NW();}
if (rand==1) {SW();}
}
if (y==0) {
rand=(int)((Math.random())*2);
System.out.println(rand);
if (rand==0) {SW();}
if (rand==1) {SE();}
}
if (x==getWidth()) {
rand=(int)((Math.random())*2);
System.out.println(rand);
if (rand==0) {NE();}
if (rand==1) {SE();}
}
if (y==getHeight()) {
rand=(int)((Math.random())*2);
System.out.println(rand);
if (rand==0) {NW();}
if (rand==1) {NE();}
}
} else {
rand=(int)((Math.random())*4);
if (rand==0) {NE();}
if (rand==1) {NW();}
if (rand==2) {SE();}
if (rand==3) {SW();}
}
}

void SW() {
x++;
y++;
while (x>0 && x<getWidth() && y>0 && y<getHeight()) {
x++;
y++;
repaint();
try {
Thread.sleep(10);
} catch (Exception e) {}
}
}

void SE() {
x--;
y++;
while (x>0 && x<getWidth() && y>0 && y<getHeight()) {
x--;
y++;
repaint();
try {
Thread.sleep(10);
} catch (Exception e) {}
}
}

void NE() {
x--;
y--;
while (x>0 && x<getWidth() && y>0 && y<getHeight()) {
x--;
y--;
repaint();
try {
Thread.sleep(10);
} catch (Exception e) {}
}
}

void NW() {
x++;
y--;
while (x>0 && x<getWidth() && y>0 && y<getHeight()) {
x++;
y--;
repaint();
try {
Thread.sleep(10);
} catch (Exception e) {}
}
}

public void paintComponent (Graphics g) {
//System.out.println(x+" "+this.getWidth()+" and "+y+" "+this.getHeight());
g.setColor(Color.WHITE);
g.fillRect(0,0,this.getWidth(),this.getHeight());

g.setColor(Color.RED);
g.fillOval(x,y,30,30);
}
}

Please edit your post and wrap the code in code tags.
See: BB Code List - Java Programming Forums - The Java Community

Unformatted code is hard to read and understand.

PHP Code:

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.Dimension;
import java.applet.AudioClip;
import java.io.*;
import java.net.*;
import java.awt.event.ItemListener;
import java.awt.event.ItemEvent;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.FlowLayout;
import java.applet.*;
import sun.audio.*;
import java.util.ArrayList;

public class go9 extends JFrame {
JTextArea displayArea;
JTextField typingArea;
static JPanel panel;
static Grp G1;
JFrame frame;
JButton button1;
JButton button2;
public static void main (String[] args) {
go9 gui = new go9();
gui.start();
}

public void start() {
frame = new JFrame();
G1= new Grp();
frame.repaint();
panel=new JPanel (new GridLayout(1,2));

button1 = new JButton("Buttons #1");
button1.addActionListener(new B1Listener());
button2 = new JButton("Button #2");
button2.addActionListener(new B2Listener());
panel.add(button1);
panel.add(button2);

frame.getContentPane().add(G1, BorderLayout.CENTER);
frame.getContentPane().add(panel, BorderLayout.PAGE_END);

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOS E);
frame.setSize(400,400);
frame.setVisible(true);
//     for (int i=0; i<10; i++) {G1.run();}


}

class B1Listener implements ActionListener {
public void actionPerformed (ActionEvent e) {G1.run();}
}
class B2Listener implements ActionListener {
public void actionPerformed (ActionEvent e) {System.out.println(e.getID());}
}
}

class Grp extends JPanel {
static int x=100;
static int y=100;
int rand;
void run() {
if (x==0 || x==getWidth() || y==0 || y==getHeight()) {
if (x==0) {
rand=(int)((Math.random())*2);
System.out.println(rand);
if (rand==0) {NW();}
if (rand==1) {SW();}
}
if (y==0) {
rand=(int)((Math.random())*2);
System.out.println(rand);
if (rand==0) {SW();}
if (rand==1) {SE();}
}
if (x==getWidth()) {
rand=(int)((Math.random())*2);
System.out.println(rand);
if (rand==0) {NE();}
if (rand==1) {SE();}
}
if (y==getHeight()) {
rand=(int)((Math.random())*2);
System.out.println(rand);
if (rand==0) {NW();}
if (rand==1) {NE();}
}
} else {
rand=(int)((Math.random())*4);
if (rand==0) {NE();}
if (rand==1) {NW();}
if (rand==2) {SE();}
if (rand==3) {SW();}
}
}

void SW() {
x++;
y++;
while (x>0 && x<getWidth() && y>0 && y<getHeight()) {
x++;
y++;
repaint();
try {
Thread.sleep(10);
} catch (Exception e) {}
}
}

void SE() {
x--;
y++;
while (x>0 && x<getWidth() && y>0 && y<getHeight()) {
x--;
y++;
repaint();
try {
Thread.sleep(10);
} catch (Exception e) {}
}
}

void NE() {
x--;
y--;
while (x>0 && x<getWidth() && y>0 && y<getHeight()) {
x--;
y--;
repaint();
try {
Thread.sleep(10);
} catch (Exception e) {}
}
}

void NW() {
x++;
y--;
while (x>0 && x<getWidth() && y>0 && y<getHeight()) {
x++;
y--;
repaint();
try {
Thread.sleep(10);
} catch (Exception e) {}
}
}

public void paintComponent (Graphics g) {
//System.out.println(x+" "+this.getWidth()+" and "+y+" "+this.getHeight());
g.setColor(Color.WHITE);
g.fillRect(0,0,this.getWidth(),this.getHeight());

g.setColor(Color.RED);
g.fillOval(x,y,30,30);
}
} 


Your code is still unformatted. There are no indentions at each {} pair.
Your posted code is still all start in the left most column. It should look something like this:

 static void pyrmin(int i,int j,int x,int z)  {           
    if (i>0)     {
            System.out.print("a");
            i--;
    } else     {
            System.out.print("b");
            j++;
    }

The indentations should be 3-4 spaces

Alright. I have added comments to the code to explain the logic to it (See above).
As I have explained - when the animation runs automatically (with no buttons involved) it runs great. But when I try to activate it by the button - it simply doesn't respond well.

If calling the run method works as you want it to, change the actionPerformed method to start a new Thread that calls the run method.
The problem with calling the run method directly in the actionPerformed method is that that method is executing on the GUI's thread which prevents repaint() from being called until the actionPerformed method returns, which it doesn't do for several seconds while run() is executing.

Threads. Alright, thanks. Haven't got there yet in the book, so it will take me some time. Again - thanks!