Re: Event Dispatching Thread Problem

Knute Johnson <>
Thu, 14 Jan 2010 20:42:01 -0800
On 1/14/2010 3:54 PM, Thanasis wrote:

i describe what i want to achieve.
 From within run method I call repaint() which in turn calls paint().
The paint() includes a for loop.
In the 1st iteration I draw a rectangle say at point(x,y). Then the
Thread sleeps 2 seconds.
In the 2nd iteration I draw another rectangle at some other point
(x+i,y+i).Then the Thread sleeps 2 seconds.
And so on.
During this drawing process I want that a user be able to stop the
applet by pressing a button.

Here's one way to do that.

import java.awt.*;
import java.awt.event.*;
import java.util.*;

public class test extends Canvas implements ActionListener,Runnable {
     private final ArrayList<Rect> list = new ArrayList<Rect>();
     private volatile boolean drawingFlag;
     private final Random rand = new Random(System.currentTimeMillis());
     private volatile int count;
     private volatile Thread thread;

     public test() {
         setPreferredSize(new Dimension(400,300));

     public void actionPerformed(ActionEvent ae) {
         String ac = ae.getActionCommand();
         if (ac.equals("Draw")) {
             if (drawingFlag)
             int w = getWidth();
             int h = getHeight();
             Rect rect = new Rect(
              new Color(rand.nextInt()));
             drawingFlag = true;
             thread = new Thread(this);
         } else if (ac.equals("Stop")) {

     public void run() {
         try {
             for (int i=0; i<=list.size(); ++i) {
                 count = i;
         } catch (InterruptedException ie) {
         drawingFlag = false;

     public void paint(Graphics g) {
         for (int i=0; count>0 && i<count; i++) {
             Rect rect = list.get(i);

     class Rect extends Rectangle {
         public Color color;

         public Rect(int x, int y, int width, int height, Color color) {
             this.color = color;

     public static void main(String[] args) {
         test t = new test();
         final Frame f = new Frame();
         f.addWindowListener(new WindowAdapter() {
             public void windowClosing(WindowEvent we) {
         Button b = new Button("Draw");
         Button s = new Button("Stop");


Knute Johnson
email s/nospam/knute2010/

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