Found a simple JComboBox sample on java2 and expanded it to include both a DocumentListener and KeyListener hoping to capture keystrokes done within the JComboBox.

Eventually those keystrokes will be captured to display the data which matches the keys entered. For example, as the user types APP, all records beginning with A is return then AP is return and then all data beginning with APP. Basically doing a Filter on "APP*".

But for now, I am unable to get either a KeyListener or DocumentListener working.

Actually, it works sporadically and can't narrow down why. It seems to only work for the Enter key but would like for it to capture for all keystrokes.

Here is the code.

import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

import javax.swing.ComboBoxEditor;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
import javax.swing.plaf.metal.MetalFileChooserUI;

public class JComboBoxFilter extends JPanel implements ItemListener {
  public JComboBoxFilter () {
      JComboBox jc = new JComboBox(); 
      jc.addItem("A"); 
      jc.addItem("AA");
      jc.addItem("AAA");
      
      jc.addItem("C"); 
      jc.addItem("CC");
      jc.addItem("CCC");

      jc.addItem("B"); 
      jc.addItem("BB"); 
      jc.addItem("BBB"); 
      jc.addItemListener(this);
      add(jc);
      ComboBoxEditor editor = jc.getEditor();
      JTextField textField = (JTextField)editor.getEditorComponent();

      textField.addKeyListener(new KeyListener()
      {

        @Override
        public void keyPressed(KeyEvent arg0) {
            runThisKeyListener();
            
        }

        @Override
        public void keyReleased(KeyEvent arg0) {
            runThisKeyListener();
            
        }

        @Override
        public void keyTyped(KeyEvent arg0) {
            runThisKeyListener();
            
        }
        
        private void runThisKeyListener()
        {
            System.out.println("Inside runThisKeyListener() : " + textField.getText());
        }
      });
      
      
      DocumentListener textFieldDL = new DocumentListener()
      {
              @Override
              public void insertUpdate(DocumentEvent e) 
              {
                  runThis();
              }

              @Override
              public void removeUpdate(DocumentEvent e) 
              {
                  runThis();
              }

              @Override
              public void changedUpdate(DocumentEvent e) 
              {
                  runThis();
              }

              private void runThis()
              {
                  System.out.println("Inside runThis() : " + textField.getText());
              }
      };
      
      textField.getDocument().addDocumentListener(textFieldDL);
      
  }

  public void itemStateChanged(ItemEvent ie) {
      String s = (String)ie.getItem(); 
      System.out.println(s); 
  }

  public static void main(String[] args) {
    JFrame frame = new JFrame();
    frame.getContentPane().add(new JComboBoxFilter ());

    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setSize(200, 200);
    frame.setVisible(true);
  }

}

Is there anything wrong with the code or is there a Java rule or restriction not allowing this type of functionality?