Swing Hack 6: Ghost Mouse

I've been playing with Swing a lot lately for my new series of articles. In my research I came across another interesting class java.awt.Robot. It's a class that can automate the UI, mainly for testing. One particularly cool feature is the mouseMove function. Once I saw this I got evil ideas. :) Imagine rogue java programs that move the mouse cursor to mystify and befuddle the user. Spelling out hideous horrible messages. Redrum! Redrum!. :)

But I'm getting ahead of myself. The code below illustrates the technique. This creates a window with a button. When you click on the button the mouse will swirl around in an ever expanding circle of zombie horror! Or maybe just in a circle. Anyway, it was a good excuse to brush up on my parametric equations. Have fun!

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.awt.Robot;

public class GhostMouse {
public static Dimension size;
public static void main(String[] args) throws Exception {
Robot robot = new Robot();
size = Toolkit.getDefaultToolkit().getScreenSize();

JFrame frame = new JFrame("Ghost Mouse (tm)!");
JButton button = new JButton("Gho Ghost");
button.addActionListener(new CircleListener(robot));


class CircleListener implements ActionListener {
Robot robot;
public CircleListener(Robot robot) {
this.robot = robot;

public void actionPerformed(ActionEvent evt) {
int originx = (int)GhostMouse.size.getWidth()/2;
int originy = (int)GhostMouse.size.getHeight()/2;
double pi = 3.1457;

for(double theta = 0; theta < 4*pi; theta=theta+0.1) {
double radius = theta * 20;
double x = Math.cos(theta) * radius + originx;
double y = Math.sin(theta) * radius + originy;
try{Thread.sleep(25);} catch (Exception ex) { }
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Posted December 9th, 2003

Tagged: java swing-hacks java.net