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Thread: MouseMotionListener is not updating my variable

  1. #1
    Junior Member
    Join Date
    Jan 2010
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    Default [SOLVED]MouseMotionListener is not updating my variable


    I've been having some trouble finding a way writing the code for a pupil following the mouse cursor and staying inside of the bounds. I've got all the math right, but I don't think my mouselistener is getting updated when I move my mouse. All feedback is highly appreciated.

    PS: I am not very good at writing code, so the tiniest mistake could be the solution.

    import java.awt.*;
    import java.awt.geom.*;
    import java.awt.geom.Ellipse2D.Double;
    import javax.swing.*;
    import java.awt.event.*;
    public class oving3stuff extends JApplet{
    	public static void main (String[]args) {
    		JFrame frame = new JFrame();
    		JApplet applet = new oving3stuff();
    	public void init() {
    		JPanel panel = new oving3panel();
    class oving3panel extends JPanel implements MouseMotionListener{
    	private Ellipse2D.Double eye, pupil;
    	private Point2D.Double eyeCenter, pupilCenter;
    	private Point mouseHere = new Point();
    	Point testPoint = new Point(0,0);
    	private double w, h;
    	private double oX, oY, x, y;
    	private double eyeRadius, pupilRadius;
    	public oving3panel() {
    		setPreferredSize(new Dimension(640, 480));
    	@Override public void paintComponent(Graphics g) {
    		Graphics2D g2 = (Graphics2D)g;
    		w = this.getWidth(); h = this.getHeight();
    		oX = w/2; oY = h/2; x = w/20; y = h/20;
    		eyeCenter = new Point2D.Double(oX, oY);
    		eyeRadius = x*5;
    		pupilRadius = x*2;
    		pupilCenter = getPupilCenterLoc(eyeCenter, mouseHere);
    		eye = new Ellipse2D.Double(oX-(x*5), oY-(y*5), x*10, y*10);
    		pupil = new Ellipse2D.Double(pupilCenter.x, pupilCenter.y, pupilRadius, pupilRadius);
    		g2.drawLine(0, (int)oY, (int)w, (int)oY);
    		g2.drawLine((int)oX, 0, (int)oX, (int)h);
    	private Point2D.Double getPupilCenterLoc(Point2D.Double eyeCenter, Point mousePoint) {
    		double x1 = eyeCenter.x;
    		double y1 = eyeCenter.y;
    		double mouseX = mousePoint.getX();
    		double mouseY = mousePoint.getY();
    		Point2D.Double refPoint = new Point2D.Double(mouseX, mouseY);
    		double distance = getDistance(eyeCenter, refPoint);
    		double radius = eyeRadius - pupilRadius;
    		double x2 = x1 + ((mouseX - x1)*(radius/distance));
    		double y2 = y1 + ((mouseY - y1)*(radius/distance));
    		return new Point2D.Double(x2, y2);
    	private double getDistance(Point2D.Double p1, Point2D.Double p2) {
    		return Math.sqrt(square(p1.x - p2.x) + square(p1.y - p2.y));
    	private double square(double d) {
    		return d*d;
    	public void mouseDragged(MouseEvent e) {}
    	public void mouseMoved(MouseEvent e) {
    		mouseHere = e.getPoint();

    When I run this code, the output is the picture under, where the smaller circle isn't moving when I move my cursor.

    Thanks in advance
    //Ole Martin
    Last edited by olemagro; February 8th, 2010 at 03:43 PM.

  2. #2
    Junior Member
    Join Date
    Jan 2010
    Thanked 0 Times in 0 Posts

    Default Re: MouseMotionListener is not updating my variable

    I forgot to add the listener to the constructor in the JPanel class. Minor but fatal error.

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