Author: Real Gagnon
Author's WebSite: http://tactika.com/realhome/realhome.html

 import java.awt.*;
 import com.sun.java.swing.*;
 import com.sun.java.swing.text.*;
 import com.sun.java.swing.event.*;
 //import javax.swing... *  if Java 2;

 public class tswing extends JApplet implements DocumentListener{
   JButton button;
   JTextField textfield;
   Document document;
   public void init() {
     getContentPane().setLayout(new FlowLayout());
     textfield = new JTextField(10);
     getContentPane().add(textfield);
     document = textfield.getDocument();
     document.addDocumentListener(this);
     button = new JButton("foo");
     getContentPane().add(button);
     button.setEnabled(false);
     }

    public void changedUpdate(DocumentEvent e ) {
      if (e.getDocument()==document) 
        disableIfEmpty(document);
       }   
      
    public void insertUpdate( DocumentEvent e ){
      if (e.getDocument()==document)
        disableIfEmpty(document);
       }   

    public void removeUpdate( DocumentEvent e ){
      if (e.getDocument()==document) 
        disableIfEmpty(document);
       }   

    public void disableIfEmpty(Document d) {
       button.setEnabled(d.getLength() > 0);
       }
 }

NOTE: With the JDK1.2 release, it's recommended to use

 import javax.swing.*;

instead of

 import com.sun.java.swing.*;

Posted On: 5-Jul-1999

internet.commerce