Mouse Motion Issue

Question

Hi,
I have the following code:
     class MouseMotionHandler extends MouseMotionAdapter {
          public void mouseMoved(MouseEvent m) {
               int x  = m.getX();
               int y  = m.getY();
               int or = mapx[y*800+x];
               country = INDEX.getCountry(new Colour(or));
               if(country != null) {
                    //do something
     }An object country is returned depending on the position of the mouse over an image, which is represented by the array mapx. The if(country != null) statement works fine for preventing an exception being thrown if the mouse is within parts of the image which do not return an object. At the moment though, exceptions are thrown every time the mouse leaves the image area(i.e outside of the array which holds the colour of the underlying pixels). How could i modify it so that this would no longer happen? One way i thought of would be this:
     class MouseMotionHandler extends MouseMotionAdapter {
          public void mouseMoved(MouseEvent m) {
               int x  = m.getX();
               int y  = m.getY();
               if((x (greater than) 10 && x < 810) && (y (greater than)  10 && y < 410)) {
                    int or = mapx[y*800+x];
                    country = INDEX.getCountry(new Colour(or));
                    if(country != null) {
                         //do something
     }This is ok and does work but i was wondering if anyone can think of a better way in dealing with this problem.
Many thanks
Cath

Answer 1

try this code:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Test extends JFrame
     final String filename = "duke.gif";     // This is the image to be loaded
     final int columns   = 10;                    // This is the number of image columns
     final int rows  = 10;                         // This is the number of image rows
     // Note the number of columns and rows define the resolution of your mouse
     // listener... as much more cells you add to the container much more precise
     // will be the mouse listening...
     Test()
          getContentPane().setLayout(new BorderLayout());
          Image map = (new ImageIcon(filename)).getImage();
          getContentPane().add(new ImageMap(map, 10, 10), BorderLayout.CENTER);
          // The bellow line may be changed to a more suitable dimension
          setSize(300, 300);
          setVisible(true);
     static public void main(String[] args)
          new Test();
class ImageMap extends Container
     Image map = null;
     ImageMap(Image map, int width, int height)
          this.map = map;
          setLayout(new GridLayout(width, height));
          for(int i=0; i<width; i++)
               for(int j=0; j<height; j++)
                    add(new TransparentBlock("block " + i + "." + j));
     public void paint(Graphics g)
          if(map != null)
               g.drawImage(map, 0, 0, getWidth(), getHeight(), Color.white, this);
          // Note the components are not painted (transparent effect)
          // but it still active and listen the mouse events... here it is the trick
class TransparentBlock extends JComponent implements MouseListener
     public final String name;
     TransparentBlock(String name)
          this.name = name;
          addMouseListener(this);
     // Here you should process the events.. remember: each component has it own
     // position at the main frame..
     public void mouseClicked(MouseEvent e) {System.out.println("mouse clicked at the " + name);}
     public void mouseEntered(MouseEvent e) {}
     public void mouseExited(MouseEvent e) {}
     public void mousePressed(MouseEvent e) {}
     public void mouseReleased(MouseEvent e){}