Author: Nobuo Tamemasa

You can group the items in the popup window by using divider lines.

// File: BlockComboBoxExample.java
/* (swing1.1) */
//package jp.gr.java_conf.tame.swing.examples;

import java.util.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
import javax.swing.plaf.metal.*;
import javax.swing.plaf.basic.*;


/**
 * @version 1.0 12/25/98
 */  
public class BlockComboBoxExample extends JFrame {
  final String SEPARATOR = "SEPARATOR";

  public BlockComboBoxExample() {
    super("Block ComboBox Example");  
    
    String[][] str = {{"A"  ,"B"  ,"C"  },
                      {"1"  ,"2"  ,"3"  },
                      {"abc","def","ghi"}
    };
                      
    JComboBox combo = new JComboBox(makeVectorData(str));
    combo.setRenderer(new ComboBoxRenderer());
    combo.addActionListener(new BlockComboListener(combo));
    
    getContentPane().setLayout(new FlowLayout());
    getContentPane().add(combo);
    setSize(300, 100);
    setVisible(true);
  }
  
  private Vector makeVectorData(String[][] str) {
    boolean needSeparator = false;
    Vector data = new Vector();
    for (int i=0;i<str.length;i++) {
      if (needSeparator) {
        data.addElement(SEPARATOR);
      }
      for (int j=0;j<str[i].length;j++) {
        data.addElement(str[i][j]);
        needSeparator = true;
      }
    }
    return data;    
  }

  public static void main (String args[]) {
    BlockComboBoxExample frame = new BlockComboBoxExample();
    frame.addWindowListener(new WindowAdapter() {
      public void windowClosing(WindowEvent e) {
        System.exit(0);
      }
    });
  }
  
    
  class ComboBoxRenderer extends JLabel implements ListCellRenderer {
    JSeparator separator;

    public ComboBoxRenderer() {
      setOpaque(true);
      setBorder(new EmptyBorder(1, 1, 1, 1));
      separator = new JSeparator(JSeparator.HORIZONTAL);
    }

    public Component getListCellRendererComponent( JList list, 
           Object value, int index, boolean isSelected, boolean cellHasFocus) {
      String str = (value == null) ? "" : value.toString();
      if (SEPARATOR.equals(str)) {
        return separator;
      }
      if(isSelected) {
        setBackground(list.getSelectionBackground());
        setForeground(list.getSelectionForeground());
      } else {
        setBackground(list.getBackground());
        setForeground(list.getForeground());
      } 
      setFont(list.getFont());
      setText(str);
      return this;
    }  
  }
  
  class BlockComboListener implements ActionListener {
    JComboBox combo;
    Object currentItem;
    
    BlockComboListener(JComboBox combo) {
      this.combo  = combo;
      combo.setSelectedIndex(0);
      currentItem = combo.getSelectedItem();
    }
    
    public void actionPerformed(ActionEvent e) {
      String tempItem = (String)combo.getSelectedItem();
      if (SEPARATOR.equals(tempItem)) {
        combo.setSelectedItem(currentItem);
      } else {
        currentItem = tempItem;
      }
    }
  }
}

Posted On: 7-Jan-1999

internet.commerce