KeyListener VS Key Binding for JField

Question

I'm trying to do a dynamic search using JTextField, this is, I need to query a list of objects every time I strike a key (for example, I press an "A" and get all entries containing an "A", then I add an "l" and all the entries that don't have "Al" in it get filtered out, then come "Ali", "Alic" and finally "Alice" ). I don't really need to associate the keys with any specific actions, so my question is: is it enough to use KeyListener to cover this functionality?

Answer 1

I actually wouldn't use either of those tools. There is a tool that was custom built to do exactly what you are talking about. It is called a DocumentListener.

Here is a demo code.

import javax.swing.*;
import javax.swing.event.*;
import javax.swing.text.*;

public class DocumentListenerExample
{

   public static void main(String[] args)
   {
   
      JFrame frame = new JFrame();
      frame.setSize(500, 500);
      frame.setLocationByPlatform(true);
      
      JTextField field = new JTextField();
      
      Document doc = field.getDocument();
      
      doc.addDocumentListener(
         new DocumentListener()
         {
         
            public void changedUpdate(DocumentEvent e) {}
            public void removeUpdate(DocumentEvent e) {}
            
            public void insertUpdate(DocumentEvent e)
            {
               
               try
               {
                  System.out.println(e.getDocument().getText(e.getOffset(), e.getLength()));
               } 
               catch (Exception exception) 
               {
                  System.err.println(exception);
               }
            
            }
         
         }
         );
      
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(field);
      frame.setVisible(true);
   
   }

}

I extracted the Document out of my JTextField, then I added an anonymous DocumentListener to it, whose DocumentListener::insertUpdate method just prints out the String that was just inserted by using Document::getText, DocumentEvent::getOffset, and DocumentEvent::getLength.

For your purposes, you may want to just grab all of the text as opposed to just the String that was just inserted. But regardless, this gives you a decent Proof of Concept on how to do it.