Useful Code of the Day: Button fires events while held

Question

Have you ever been making a GUI application with Swing and used some JButtons? Fun, right? Have you ever wanted to have the button fire action events while the button was being held down? Well, if you just stick a plain JButton in your application and press and hold the mouse button on it, you'll see it doesn't do anything except sit there looking pressed in. Insolent button!
RepeatButton (code below, couldn't think of a better name) is a JButton subclass which contains a timer that is set when the mouse button presses the button, and after a slight initial delay (configurable), fires action events to all registered action listeners repeatedly (with another configurable delay between events) until either the mouse is released or the mouse moves out of the button (it starts up again if the mouse moves back over without releasing the mouse button) or the button is disabled. The event modifiers are passed on as well, so you know if the shift or control buttons (or whatever) are being pressed at the same time.
There is also a method to disable the repeated action firing while holding. This, in effect, turns the button into a normal JButton, if needed.
There is a main method for testing which will show a button in a frame and print out the action command for each action event fired.
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import javax.swing.*;
import javax.swing.event.*;
* <code>RepeatButton</code> is a <code>JButton</code> which contains a timer
* for firing events while the button is held down.  There is a default
* initial delay of 300ms before the first event is fired and a 60ms delay
* between subsequent events.  When the user holds the button down and moves
* the mouse out from over the button, the timer stops, but if the user moves
* the mouse back over the button without having released the mouse button,
* the timer starts up again at the same delay rate.  If the enabled state is
* changed while the timer is active, it will be stopped.
* NOTE:  The normal button behavior is that the action event is fired after
* the button is released.  It may be important to konw then that this is
* still the case.  So in effect, listeners will get 1 more event then what
* the internal timer fires.  It's not a "bug", per se, just something to be
* aware of.  There seems to be no way to suppress the final event from
* firing anyway, except to process all ActionListeners internally.  But
* realistically, it probably doesn't matter. 
public class RepeatButton extends JButton
          implements ActionListener, MouseListener {
      * The pressed state for this button.
     private boolean pressed = false;
      * Flag to indicate that the button should fire events when held. 
      * If false, the button is effectively a plain old JButton, but
      * there may be times when this feature might wish to be disabled. 
     private boolean repeatEnabled = true;
      * The hold-down timer for this button.
     private Timer timer = null;
      * The pressed state for this button.
     private int delay = 60;
      * The pressed state for this button.
     private int initialDelay = 300;
      * Holder of the modifiers used when the mouse pressed the button. 
      * This is used for subsequently fired action events.  This may change
      * after mouse pressed if the user moves the mouse out, releases a key
      * and then moves the mouse back in. 
     private int modifiers = 0;
      * Creates a button with no set text or icon.
     public RepeatButton() {
          super();
          init();
      * Creates a button where properties are taken from the Action supplied.
      * @param  a  the button action
     public RepeatButton(Action a) {
          super(a);
          init();
      * Creates a button with an icon.
      * @param  icon  the button icon
     public RepeatButton(Icon icon) {
          super(icon);
          init();
      * Creates a button with text.
      * @param  text  the button text
     public RepeatButton(String text) {
          super(text);
          init();
      * Creates a button with initial text and an icon.
      * @param  text  the button text
      * @param  icon  the button icon
     public RepeatButton(String text, Icon icon) {
          super(text, icon);
          init();
      * Initializes the button.
     private void init() {
          this.addMouseListener(this);
          // initialize timers for button holding...
          this.timer = new Timer(this.delay, this);
          this.timer.setRepeats(true);
      * Gets the delay for the timer of this button. 
      * @return  the delay
     public int getDelay() {
          return this.delay;
      * Set the delay for the timer of this button. 
      * @param  d  the delay
     public void setDelay(int d) {
          this.delay = d;
      * Gets the initial delay for the timer of this button. 
      * @return  the initial delay
     public int getInitialDelay() {
          return this.initialDelay;
      * Sets the initial delay for the timer of this button. 
      * @param  d  the initial delay
     public void setInitialDelay(int d) {
          this.initialDelay = d;
      * Checks if the button should fire events when held.  If false, the
      * button is effectively a plain old JButton, but there may be times
      * when this feature might wish to be disabled. 
      * @return  if true, the button should fire events when held
     public boolean isRepeatEnabled() {
          return this.repeatEnabled;
      * Sets if the button should fire events when held.  If false, the
      * button is effectively a plain old JButton, but there may be times
      * when this feature might wish to be disabled.  If false, it will
      * also stop the timer if it's running.
      * @param  en  if true, the button should fire events when held
     public void setRepeatEnabled(boolean en) {
          if(!en) {
               this.pressed = false;
               if(timer.isRunning()) {
                    timer.stop();
          this.repeatEnabled = en;
      * Sets the enabled state of this button.  Overridden to stop the timer
      * if it's running.
      * @param  en  if true, enables the button
     public void setEnabled(boolean en) {
          if(en != super.isEnabled()) {
               this.pressed = false;
               if(timer.isRunning()) {
                    timer.stop();
          super.setEnabled(en);
      * Handle action events.
      * @param  ae  the action event
     public void actionPerformed(ActionEvent ae) {
          // process events only from this components
          if(ae.getSource() == this.timer) {
               ActionEvent event = new ActionEvent(
                    this, ActionEvent.ACTION_PERFORMED,
                    super.getActionCommand(), this.modifiers);
               super.fireActionPerformed(event);
          // testing code...
          else if(testing && ae.getSource() == this) {
               System.out.println(ae.getActionCommand());
      * Handle mouse clicked events.
      * @param  me  the mouse event
     public void mouseClicked(MouseEvent me) {
          // process events only from this components
          if(me.getSource() == this) {
               this.pressed = false;
               if(this.timer.isRunning()) {
                    this.timer.stop();
      * Handle mouse pressed events.
      * @param  me  the mouse event
     public void mousePressed(MouseEvent me) {
          // process events only from this components
          if(me.getSource() == this && this.isEnabled() && this.isRepeatEnabled()) {
               this.pressed = true;
               if(!this.timer.isRunning()) {
                    this.modifiers = me.getModifiers();
                    this.timer.setInitialDelay(this.initialDelay);
                    this.timer.start();
      * Handle mouse released events.
      * @param  me  the mouse event
     public void mouseReleased(MouseEvent me) {
          // process events only from this components
          if(me.getSource() == this) {
               this.pressed = false;
               if(this.timer.isRunning()) {
                    this.timer.stop();
      * Handle mouse entered events.
      * @param  me  the mouse event
     public void mouseEntered(MouseEvent me) {
          // process events only from this components
          if(me.getSource() == this && this.isEnabled() && this.isRepeatEnabled()) {
               if(this.pressed && !this.timer.isRunning()) {
                    this.modifiers = me.getModifiers();
                    this.timer.setInitialDelay(this.delay);
                    this.timer.start();
      * Handle mouse exited events.
      * @param  me  the mouse event
     public void mouseExited(MouseEvent me) {
          // process events only from this components
          if(me.getSource() == this) {
               if(this.timer.isRunning()) {
                    this.timer.stop();
      * Testing flag.  Set in main method.
     private static boolean testing = false;
      * Main method, for testing.  Creates a frame with both styles of menu.
      * @param  args  the command-line arguments
     public static void main(String[] args) {
          testing = true;
          JFrame f = new JFrame("RepeatButton Test");
          f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          JPanel p = new JPanel();
          RepeatButton b = new RepeatButton("hold me");
          b.setActionCommand("test");
          b.addActionListener(b);
          p.add(b);
          f.getContentPane().add(p);
          f.pack();
          f.show();
"Useful Code of the Day" is supplied by the person who posted this message. This code is not guaranteed by any warranty whatsoever. The code is free to use and modify as you see fit. The code was tested and worked for the author. If anyone else has some useful code, feel free to post it under this heading.

Answer 1

This makes word completion possible for JTextArea:
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import javax.swing.event.*;
import javax.swing.text.*;
import java.util.*;
* This class provides word completion for JTextArea.
public class WordCompleteArea extends JTextArea {
    private boolean isTextComplete = true;
    public WordCompleteArea (Document doc, String text,
                                  int rows, int columns, KeyStroke expandKey) {
        super (doc, text, rows, columns);
        String s = "word-complete";
        Action wordComplete = new AbstractAction () {
            public void actionPerformed (ActionEvent e) {
                wordComplete ();
        getInputMap ().put (expandKey, s);
        getActionMap ().put (s, wordComplete);
    public WordCompleteArea (Document doc, String text, int rows, int columns) {
        this (doc, text, rows, columns,
                        KeyStroke.getKeyStroke ("ctrl pressed SPACE"));
    public WordCompleteArea (Document doc) {
        this (doc, null, 0, 0);
    public WordCompleteArea (String text, int rows, int columns) {
        this (new PlainDocument (), text, rows, columns);
    public WordCompleteArea (int rows, int columns) {
        this (null, rows, columns);
    public WordCompleteArea (String text) {
        this (text, 0, 0);
    public WordCompleteArea () {
        this (0, 0);
     * Define if text already written in the JTextArea will be used
     * for expansion.
    public void setTextComplete (boolean b) {
        isTextComplete = b;
     * Find out if text already written in the JTextArea will be used
     * for expansion.
    public boolean isTextComplete () {
        return isTextComplete;
    private String tokenDelimiters = "\t\r\n ,;()[]{}%+/-*<>=&|!\"\'.@#";
     * Get delimiters that form a word.
    public String getTokenDelimiters () {
        return tokenDelimiters;
     * Set delimiters that form a word.
    public void setTokenDelimiters (String s) {
        tokenDelimiters = s;
    // Additional words used for expansion.
    private LinkedList wordCompleteList = new LinkedList ();
     * Add words that will be used as expansion.
    public void addCompleteWords (java.util.List words) {
        wordCompleteList.add (words);
     * Add a word that will be used as expansion.
    public void addCompleteWord (String word) {
        wordCompleteList.add (word);
    private String lastExpanded = null;
    private String lastExpansion = null;
    private Set dontAccept = new HashSet ();
    protected void wordComplete () {
        int caret = getCaretPosition ();
        if (caret == 0)
            return;
        String text = getText ();
        if (caret != text.length () && isCompletionLetter (text.charAt (caret)))
            return;
        StringBuffer sb = new StringBuffer ();
        int index = caret - 1;
        char ch;
        while (index >= 0 && isCompletionLetter ((ch = text.charAt (index)))) {
            sb.append (ch);
            index--;
        if (sb.length () == 0)
            return;
        sb.reverse ();
        String word = sb.toString ();
        String toExpand = word;
        if (toExpand.equals (lastExpansion)) {
            dontAccept.add (lastExpansion);
            toExpand = lastExpanded;
        } else {
            dontAccept.clear ();
        String s = findExpansion (toExpand, caret);
        if (s != null) {
            lastExpanded = toExpand;
            lastExpansion = s;
            replaceRange (s, caret - word.length (), caret);
        } else {
            dontAccept.clear ();
            lastExpanded = null;
            lastExpansion = null;
            int diff = word.length () - toExpand.length ();
            replaceRange ("", caret - diff, caret);
    private boolean isCompletionLetter (char ch) {
        return tokenDelimiters.indexOf (ch) < 0;
    protected String findExpansion (String word, int caret) {
        StringTokenizer st;
        if (isTextComplete) {
            st = new StringTokenizer (getText (), getTokenDelimiters ());
            while (st.hasMoreTokens ()) {
                String s = st.nextToken ();
                if (    s.startsWith (word)
                        && s.length () != word.length ()
                        && !dontAccept.contains (s)      ) {
                    return s;
        for (Iterator it = wordCompleteList.iterator (); it.hasNext (); ) {
            st = new StringTokenizer
                            ((String) it.next (), getTokenDelimiters ());
            while (st.hasMoreTokens ()) {
                String s = st.nextToken ();
                if (    s.startsWith (word)
                        && s.length () != word.length ()
                        && !dontAccept.contains (s)      ) {
                    return s;
        return null;
    // TEST
    public static void main (String[] args) {
        WordCompleteArea a = new WordCompleteArea ();
        JFrame window = new JFrame ();
        window.getContentPane ().add (a, BorderLayout.CENTER);
        window.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
        window.setSize (300, 300);
        window.setVisible (true);
}