Using Gradients in motion

Question

I'm working on a project that has used the DnD package to create an interface where users can create various shaped objects and drag them about the screen. The user can change the colour of the objects. I'm trying to make it possible for the user to select a gradient instead of just a colour. However, when the object is made gradient, the gradient changes as I move the object. Is seems like the gradient is set to the background, and then the shape allows you to see through to the background.
Does anyone have any ideas on how to keep the gradient consistant as the object moves?
I don't know how helpful this code will be out of context, but here it is:
     public void drawObject(Graphics2D g2) {
          /* Fill shape */
          g2.setColor(((NodeStyleSheet) attributes).getBackgroundColor());
          g2.setPaint(theGradient);
          if (drawableShape == null )
               g2.fill( ShapeObject.getObject(ShapeObject.DEFAULT_NAME).getShape());
          else
               g2.fill(drawableShape);
Thank you
Brina

Answer 1

import java.awt.*;
import java.awt.geom.Ellipse2D;
import javax.swing.*;
public class GradientMotion extends JPanel
    Ellipse2D.Double ball;
    int dx = 2;
    int dy = 1;
    public GradientMotion()
        ball = new Ellipse2D.Double(50, 50, 50, 50);
    protected void paintComponent(Graphics g)
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);
        Rectangle r = ball.getBounds();
        int x = r.x + r.width;
        int y = r.y + r.height;
        GradientPaint gradient = new GradientPaint(r.x, r.y, Color.blue,
                                                   x, y, Color.yellow);
        g2.setPaint(gradient);
        g2.fill(ball);
    public void moveBall()
        checkBoundries();
        ball.x += dx;
        ball.y += dy;
        repaint();
    private void checkBoundries()
        if(ball.x + dx < 0 || ball.x + ball.width + dx > getWidth())
            dx *= -1;
        if(ball.y + dy < 0 || ball.y + ball.height + dy > getHeight())
            dy *= -1;
    public static void main(String[] args)
        GradientMotion gradientMotion = new GradientMotion();
        Locomoter locomoter = new Locomoter(gradientMotion);
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(gradientMotion);
        f.setSize(400,400);
        f.setLocation(200,200);
        f.setVisible(true);
        locomoter.start();
class Locomoter implements Runnable
    GradientMotion gradientMotion;
    int delay = 25;
    boolean animate = false;
    Thread thread;
    public Locomoter(GradientMotion gm)
        gradientMotion = gm;
    public void run()
        while(animate)
            try
                Thread.sleep(delay);
            catch(InterruptedException ie)
                System.err.println(ie.getMessage());
            gradientMotion.moveBall();
    public void start()
        if(!animate)
            animate = true;
            thread = new Thread(this);
            thread.setPriority(Thread.NORM_PRIORITY);
            thread.start();
}