import javax.swing.*;
import java.awt.*;
import java.util.*;

/** Simple custom cell renderer. The idea here is to augment
 *  the default renderer instead of building one from scratch. 
 *  The advantage of this approach is that you don't have to 
 *  handle the highlighting of the selected entries yourself, 
 *  plus values that aren't of the new type you want to draw can 
 *  be handled automatically. The disadvantage is that you are 
 *  limited to a variation of a JLabel, which is what the default 
 *  renderer returns.
 *  <P>
 *  Note that this method can get called lots and lots of times
 *  as you click on entries. We don't want to keep generating 
 *  new ImageIcon objects, so we make a Hashtable that associates 
 *  previously displayed values with icons, reusing icons for 
 *  entries that have been displayed already.
 *  <P>
 *  Note that in the first release of JDK 1.2, the default 
 *  renderer  has a bug: the renderer doesn't clear out icons for 
 *  later entries. So if you mix plain strings and ImageIcons in 
 *  your JList, the plain strings still get an icon. The 
 *  call below clears the old icon when the value is not a 
 *  JavaLocation.
 *
 *  Taken from Core Web Programming from 
 *  Prentice Hall and Sun Microsystems Press,
 *  http://www.corewebprogramming.com/.
 *  &copy; 2001 Marty Hall and Larry Brown;
 *  may be freely used or adapted. 
 */

public class JavaLocationRenderer extends 
                                  DefaultListCellRenderer {
  private Hashtable iconTable = new Hashtable();
  
  public Component getListCellRendererComponent(JList list,
                                                Object value,
                                                int index,
                                                boolean isSelected,
                                                boolean hasFocus) {
    // First build the label containing the text, then 
    // later add the image.
    JLabel label =
      (JLabel)super.getListCellRendererComponent(list,
                                                 value,
                                                 index,
                                                 isSelected,
                                                 hasFocus);
    if (value instanceof JavaLocation) {
      JavaLocation location = (JavaLocation)value;
      ImageIcon icon = (ImageIcon)iconTable.get(value);
      if (icon == null) {
        icon = new ImageIcon(location.getFlagFile());
        iconTable.put(value, icon);
      }
      label.setIcon(icon);
    } else {
      // Clear old icon; needed in 1st release of JDK 1.2.
      label.setIcon(null); 
    }
    return(label);
  }
}