How disable button when nothing in textfield

Question

I have a quick question. Im making a little program here but now im stuck on a point.

I have a TextField and a button with which you can see the amount if you click on it. But i want to disable the button when nothing is written in the TextField, so when you write something in the textfield the button must be able to press again.

Can anyone help me on this? i've been searching for a answer but i cant find it.

Thank you.

Answer 1

Simple! All you need to do is add an listener to the document created for the text field you are using and then call an enable method whenever a change is detected. Within this method you enable the button

Eg

textField.getDocument().addDocumentListener(new DocumentListener() {
  public void changedUpdate(DocumentEvent e) {
    enableButton();
  }
  public void removeUpdate(DocumentEvent e) {
    enableButton();
  }
  public void insertUpdate(DocumentEvent e) {
    enableButton();
}

public void enableButton() {
     if (textField.getText().equals(""))
     {
        button.setEnabled(false);
     }
     else
     {
        button.setEnabled(true);
     }
  }
});

Answer 2

Already discussed. This link might help Disable button whenever a text field is empty dynamically

If you are not looking for it, please be specific.

Answer 3

 /*
     * jsch-0.1.50 - MyPane.java, Feb 3, 2014 3:05:03 PM
     * 
     * Copyright 2014 Varra Ltd, Inc. All rights reserved.
     * Varra proprietary/confidential. Use is subject to license terms.
     */
    package com.varra.threading.voltaile;

    import java.awt.event.ActionEvent;
    import java.awt.event.ActionListener;

    import javax.swing.JButton;
    import javax.swing.JFrame;
    import javax.swing.JPanel;
    import javax.swing.JTextField;

    /**
     * TODO Description go here.
     * 
     * @author <a href="mailto:varra@outlook.com">Rajakrishna V.
     *         Reddy</a>
     * @version 1.0
     * 
     */
    public class MyPane extends JPanel
    {

        /** The Constant serialVersionUID. */
        private static final long serialVersionUID = 3089223598850357054L;

        /** The tf. */
        final JTextField tf = new JTextField(30);

        /** The button. */
        final JButton button = new JButton("BUTTON");

        /**
         * Instantiates a new my pane.
         */
        public MyPane()
        {
            add(tf);
            add(button);
            button.setEnabled(false);
            new Thread(target).start();
            tf.addActionListener(actionListener);
        }

        final ActionListener actionListener = new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                if (e.getActionCommand().equalsIgnoreCase("Enable"))
                {
                    button.setEnabled(true);
                }
                else if (e.getActionCommand().equalsIgnoreCase("Disable"))
                {
                    button.setEnabled(false);
                }
            }
        };

        final Runnable target = new Runnable()
        {

            public void run()
            {
                while (true)
                {
                    final ActionListener[] listeners = tf.getActionListeners();
                    for (ActionListener listener : listeners)
                    {
                        if (tf.getText().trim().length() > 0)
                        {
                            final ActionEvent event = new ActionEvent(tf, 1, "Enable");
                            listener.actionPerformed(event);
                        }
                        else
                        {
                            final ActionEvent event = new ActionEvent(tf, 1, "Disable");
                            listener.actionPerformed(event);
                        }
                    }
                }
            }
        };

        /**
         * Entry point to the entire application, contains the list of args to pass
         * the user defined values.
         * 
         * @param args
         *            the arguments
         */
        public static void main(String... args)
        {
            final JFrame frame = new JFrame();
            frame.getContentPane().add(new MyPane());
            frame.setSize(800, 600);
            frame.setVisible(true);
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        }
    }