Getting Relative Mouse Coordinates

[Brandon Tom]

Say I have a 400 x 400 JPanel in the middle of a 500 x 500 JFrame. The JPanel has string drawn to it that prints out the mouse coordinates. If my mouse were placed exactly in the middle of the JFrame, the string should read (200, 200). What is the best way to accomplish this?

I've used java.awt.MouseInfo but that has only helped me get the position of the mouse relative to the entire screen.
[ March 23, 2006: Message edited by: Brandon Tom ]

[Sam Codean]

Add a MouseListener to the JPanel. Implements the MouseEntered method. This will have a parameter for the Mouse Event from which you will get the Mouse Co ordinates relative to the JPanel.
hope that helps, Please get back to me in case you have doubts

[Brandon Tom]

Actually, I needed to implement the MouseMotionListener and provide an implementation for mouseMoved (). Thanks anyway!

[Craig Wood]

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
 
public class MouseTest
{
    JLabel label;
    JPanel child;
 
    public void setText(int x, int y)
    {
        String s = "";
        if(x > 0 && y > 0)
            s = "x = " + x + "  y = " + y;
        label.setText(s);
    }
 
    private JPanel getContent()
    {
        label = new JLabel();
        label.setHorizontalAlignment(JLabel.CENTER);
        GridBagLayout gridbag = new GridBagLayout();
        GridBagConstraints gbc = new GridBagConstraints();
        child = new JPanel(gridbag);
        child.setBorder(BorderFactory.createEtchedBorder());
        child.setPreferredSize(new Dimension(400,400));
        child.add(label, gbc);
        JPanel parent = new JPanel(gridbag);
        parent.setOpaque(true);
        parent.add(child, gbc);
        return parent;
    }
 
    public static void main(String[] args)
    {
        MouseTest test = new MouseTest();
        JPanel panel = test.getContent();
        panel.addMouseMotionListener(new MotionSensor(test));
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setContentPane(panel);
        f.setSize(500,500);
        f.setLocation(200,200);
        f.setVisible(true);
    }
}
 
class MotionSensor extends MouseMotionAdapter
{
    MouseTest mouseTest;
    boolean overChild;
 
    public MotionSensor(MouseTest mt)
    {
        mouseTest = mt;
        overChild = false;
    }
 
    public void mouseMoved(MouseEvent e)
    {
        Point p = e.getPoint();
        Rectangle r = mouseTest.child.getBounds();
        if(r.contains(p))
        {
            if(!overChild)
                overChild = true;
            // you can do this by hand
            int x = p.x - r.x;
            int y = p.y - r.y;
            mouseTest.setText(x, y);
 
            //   --- or ---
 
            // let SwingUtilities do the work
            //Component source = (Component)e.getSource();
            //Point xp = SwingUtilities.convertPoint(source, p, mouseTest.child);
            //mouseTest.setText(xp.x, xp.y);
        }
        else if(overChild)  // reset
        {
            overChild = false;
            mouseTest.setText(-1, -1);
        }
    }
}