WindowDragger.java

package com.explodingpixels.widgets;

import java.awt.Component;
import java.awt.Point;
import java.awt.Window;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionAdapter;

import javax.swing.SwingUtilities;

public class WindowDragger {

    private Window fWindow;

    private Component fComponent;

    private int dX;

    private int dY;

    public WindowDragger(Window window, Component component) {

        fWindow = window;
        fComponent = component;

        fComponent.addMouseListener(createMouseListener());
        fComponent.addMouseMotionListener(createMouseMotionListener());
    }

    private MouseListener createMouseListener() {
        return new MouseAdapter() {
            @Override
            public void mousePressed(MouseEvent e) {
                Point clickPoint = new Point(e.getPoint());
                SwingUtilities.convertPointToScreen(clickPoint, fComponent);

                dX = clickPoint.x - fWindow.getX();
                dY = clickPoint.y - fWindow.getY();
            }
        };
    }

    private MouseMotionAdapter createMouseMotionListener() {
        return new MouseMotionAdapter() {
            @Override
            public void mouseDragged(MouseEvent e) {
                Point dragPoint = new Point(e.getPoint());
                SwingUtilities.convertPointToScreen(dragPoint, fComponent);

                fWindow.setLocation(dragPoint.x - dX, dragPoint.y - dY);
            }
        };
    }

}