Mouseover with continuous updating?

[fivetenmontrail]

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.

[pbrockway2]

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.

[fivetenmontrail]

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.

[fivetenmontrail]

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.

[pbrockway2]

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

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);
			}
		});
	}
}