KeyListener kinda deaf (in simple game)

Question

Hey everyone...
I'm trying to write a simple word-guessing game (Lingo, user should guess 5 letter words etc).
I've created some custom AWT Components (sorry for the dutch naming):
Lettervak: extends Canvas
Woordveld: extends Container and contains Lettervak's
Speelveld: extends Container and contains Woordveld's
The Speelveld (playing field in english) is the main component I want to talk to from the applet itself.
I don't care where a key is typed, I just want to be able to send the message to the correct component so the letter can be drawn in a Lettervak. So I though I'd add a KeyListener to the Applet itself.
It registers (I can see in the debugger), but it doesn't receive any key events (I can tell by adding a breakpoint there, so it's not in code further down).
Can anyone tell me what I'm doing wrong? Below is the code of the Applet itself:
(may look a bit messy, because I've been fooling around to get it to work, sorry...)
package lingo;
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
public class LingoWeb
extends Applet {
private boolean isStandalone = false;
// Components
Speelveld grid;
//Get a parameter value
public String getParameter(String key, String def) {
return isStandalone ? System.getProperty(key, def) :
(getParameter(key) != null ? getParameter(key) : def);
//Construct the applet
public LingoWeb() {
this.addKeyListener( new SpeelveldListener() );
//Initialize the applet
public void init() {
try {
jbInit();
catch (Exception e) {
e.printStackTrace();
//Component initialization
private void jbInit() throws Exception {
Speelveld grid = new Speelveld( 10, 20, 5, 5, 40 );
this.setFocusable( true );
this.requestFocusInWindow();
this.setLayout(null);
this.add(grid);
this.repaint();
//Get Applet information
public String getAppletInfo() {
return "Applet Information";
//Get parameter info
public String[][] getParameterInfo() {
return null;
class SpeelveldListener implements KeyListener {
public void keyTyped( KeyEvent e ) {
char c = e.getKeyChar();
grid.invoer(c);
public void keyPressed( KeyEvent e ) {
System.out.println( e.getKeyChar() );
public void keyReleased( KeyEvent e ) {}
Thanks!
Tim.

Answer 1

/*  <applet code="AppletKeyTest" width="400"
height="300"></applet>
*  use: >appletviewer AppletKeyTest.java
import java.applet.Applet;
import java.awt.*;
import java.awt.font.*;
import java.awt.event.*;
public class AppletKeyTest extends Applet
public void init()
setLayout(new BorderLayout());
add(new Speelveld());
public static void main(String[] args)
Applet applet = new AppletKeyTest();
Frame f = new Frame(applet.getClass().getName());
f.addWindowListener(new WindowAdapter()
public void windowClosing(WindowEvent e)
System.exit(0);
f.add(applet);
f.setSize(400,300);
f.setLocation(200,200);
applet.init();
applet.start();
f.setVisible(true);
class Speelveld extends Canvas
Font font;
String text;
public Speelveld()
font = new Font("lucida bright regular", Font.PLAIN,
48);
text = "a";
addKeyListener(new SpeelveldListener(this));
setFocusable(true);
requestFocusInWindow();
public void paint(Graphics g)
super.paint(g);
Graphics2D g2 = (Graphics2D)g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
int w = getWidth();
int h = getHeight();
g2.setFont(font);
FontRenderContext frc = g2.getFontRenderContext();
float textWidth = (float)font.getStringBounds(text,
frc).getWidth();
LineMetrics lm = font.getLineMetrics(text, frc);
float x = (w - textWidth)/2;
float y = (h + lm.getHeight())/2 - lm.getDescent();
g2.drawString(text, x, y);
public void update(Graphics g)
paint(g);
public void setText(String text)
this.text = text;
repaint();
class SpeelveldListener extends KeyAdapter
Speelveld speelveld;
public SpeelveldListener(Speelveld s)
speelveld = s;
public void keyPressed(KeyEvent e)
String s = KeyEvent.getKeyText(e.getKeyCode());
speelveld.setText(s);
}Yikes!
don't do much processing in the listener methods.
Certainly DONT call drawn out methods. I wouldn't call ANY methods.
Here is a quote...
"The most important rule to keep in mind about event listeners that they should execute very quickly. Because all drawing and event-listening methods are executed in the same thread, a slow event-listener method can make the program seem unresponsive and slow to repaint itself. If you need to perform some lengthy operation as the result of an event, do it by starting up another thread (or somehow sending a request to another thread) to perform the operation. For help on using threads, see How to Use Threads."
From here.
http://java.sun.com/docs/books/tutorial/uiswing/events/generalrules.html
There are those who will tell you that calling methods and adding other
general inefficiencies to you code doesn't matter, but it in fact does and this
is one area where it is readilly apparent.
In my HyperView API my listener routines simply bit codes the event,
pops it on a list, and then calls notify() to another thread which then does the processing.
This allows more cycles for the AWT-Event thread to grab events because it doesn't
have to then process them. It also smooths out the differences between different
operating system event models.
Good Luck!
(T)