Mouseover with continuous updating?

I am currently working on a simple swing application which requires shifting the coordinates of an image. This shifting is supposed to occur whenever the mouse if over a rectangle placed near the edges of the screen. If you have played any RTS games such as Starcraft, C&C, or Warcraft 3, it is similar to their shifting movement. Currently, I can only think of writing a loop which constantly checks if the mouse is inside this rectangle, and if so, add some integer to the locations of the image. I feel this is not a proper way to use swing, so...

What is the proper way of doing this with Swing? I can't seem to find any listeners which would constantly be called when the mouse is over something. mouseMoved is the only event I could find that gave me decent results, but the image stops moving when my mouse does; I need it to continue to shift.

What about detecting mouse entered/exited events and using that to determine whether motion is currently required.

Or, again, mouse moved could be used to turn motion on or off.

I am not sure I understand you. Lets say I use mouseEntered/mouseExited or mouseMoved. The cursor is over a rectangle in the right side of the screen; therefore, I should be shifting the image. In the case for mouseEntered, shouldn't it only be called once? This would not solve my problem. mouseMoved will also no solve my problem because I need this image to continue to shift even if the mouse is not moving.

Is there some event I can set so that the swing panel will continue to call some function every update? Or trick Swing into calling mouseMoved, even though my mouse is not moving?

I am not sure you understand my problem, but if you do, I must be lacking some knowledge on how to use swing events.

I think I found a solution. I just created a swing.Timer and call it every 100ms to shift the image if the mouse was inside the rectangle. Thank you for you help though.

I think you're right to use a timer. The following is what I had in mind:

Code:

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import java.awt.Dimension;
import java.awt.Point;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.Timer;
import javax.swing.UIManager;

public class PanelEdgeEg extends JPanel {
       
        private Point target;
        private JLabel thing; // something to move
        private Timer timer;
       
        public PanelEdgeEg() {
                setLayout(null);
                addMouseListener(listener);
                addMouseMotionListener(listener);
                thing = new JLabel("*");
                add(thing);
                thing.setSize(20, 20);
                thing.setLocation(50, 50);
                timer = new Timer(100, moveAL);
        }
       
                /*
                * Mouse event are used, not to move things, but to turn
                * motion on or off.
                */
        private MouseAdapter listener = new MouseAdapter() {
                @Override
                public void mouseEntered(MouseEvent e) {
                        setTarget(e.getPoint());
                }

                @Override
                public void mouseExited(MouseEvent e) {
                        setTarget(null);
                }

                @Override
                public void mouseMoved(MouseEvent e) {
                        setTarget(e.getPoint());
                }
        };
       
        private void setTarget(Point p) {
                if(p == null) {
                        timer.stop();
                        return;
                } else {
                        target = p.getLocation();
                        if(!timer.isRunning()) {
                                timer.start();
                        }
                }
        }

                /*
                * Something to represent onscreen motion
                */
        private ActionListener moveAL = new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                        Point loc = thing.getLocation();
                        double dist = loc.distance(target);
                        int deltaX = (int)(10 * (target.x - loc.x) / dist);
                        int deltaY = (int)(10 * (target.y - loc.y) / dist);
                       
                        thing.setLocation(loc.x + deltaX, loc.y + deltaY);
                }
        };
       
        public static void main(String[] args) {
                try {
                        UIManager.setLookAndFeel( UIManager.getSystemLookAndFeelClassName());
                } catch (Exception e) {}
                final JFrame frame = new JFrame("PanelEdgeEg");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

                SwingUtilities.invokeLater(new Runnable() {
                        @Override
                        public void run() {
                                frame.add(new PanelEdgeEg());
                                frame.setSize(new Dimension(500, 500));
                                frame.setLocationRelativeTo(null);
                                frame.setVisible(true);
                        }
                });
        }
}

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