Source Code : Block ComboBox Example

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Block ComboBox Example

  
// Example from http://www.crionics.com/products/opensource/faq/swing_ex/SwingExamples.html

/* (swing1.1) */


import java.awt.Component;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.util.Vector;

import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JSeparator;
import javax.swing.ListCellRenderer;
import javax.swing.UIManager;
import javax.swing.border.EmptyBorder;

/**
 * @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[]) {
    try {
        UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
    } catch (Exception evt) {}
  
    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;
      }
    }
  }
}

           
         
    
  

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