A problem with KeyListener

[Reskaillev]

Hello everyone!

Well I did a lil' bit of Java on university but now I wanted to program an applet Pong clone.
Problem is that I can't seem to get the keyListener listening to my input...

So: How do I get my keylistener to work?

import java.applet.*;
import java.awt.*;
import java.awt.event.*; 

public class main extends Applet implements Runnable,KeyListener {

	/**
	 * 
	 */
	private static final long serialVersionUID = 2305235281454935668L;

	/**
	 * @param args
	 */
	int y;
	boolean pause;
	Graphics offscr;
	Thread runner;
	int Score[] = new int[2];
	static int height,width;
	Image offscreenImage;
	
	public void init()
		{
		pause=false;
		this.setSize(650,400);
		runner = new Thread(this);
		width = getWidth();
		height = getHeight();
		y = height/2;
		offscreenImage = createImage(width, height);
		offscr = offscreenImage.getGraphics();
		addKeyListener(this);
		runner.start();
		} 
	
	public void paint(Graphics g)
	{
		offscr.setColor(Color.black);
		offscr.fillRect(0,0,width,height);
		offscr.setColor(Color.white);
		offscr.fillRect(20,y-50,20,60);
		g.drawImage(offscreenImage, 0, 0, this);
	}
	
	public void update(Graphics g) 
	{
	paint(g);
	}
	
	@Override
	public void keyPressed(KeyEvent e) {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void keyReleased(KeyEvent e) {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void keyTyped(KeyEvent e) {
		int keyCode = e.getKeyCode();
	    switch( keyCode ) { 
	        case KeyEvent.VK_UP:
	        	y++;
				System.out.println("up");
	            break;
	        case KeyEvent.VK_DOWN:
	        	y++;
				System.out.println("up");
	            break;
	        case KeyEvent.VK_SPACE:
				if (pause)
				{ pause=false; }
				else
				{ pause=true; }
	            break;
	        case KeyEvent.VK_ESCAPE:
	            // handle right
	            break;
	     }
	}

	@Override
	public void run() {
		while (true)
		{
		repaint();
		y++;
		try
		{	
			Thread.sleep (20);
		}
		catch (InterruptedException ex){}
		}
	}

}

EDIT: I noticed it might not be necessary to get a runnable aplet for a pong clone, but I still like to know why this program wasn't working

Thanks in advance,

Reskaillev

[Norm]

Does the component with the listener have the focus?

I added a println:

	public void keyTyped(KeyEvent e) {
           System.out.println("kT e=" + e);  //<<<< Show when called

When I click on the window then press a key it prints

[pbrockway2]

I noticed it might not be necessary to get a runnable aplet for a pong clone, but I still like to know why this program wasn't working

You need to be more precise about "wasn't working". Is keyTyped() ever called? Add some debugging code (and remember to click in the applet window to give it focus)

@Override
public void keyTyped(KeyEvent e) {
    [color=green]System.out.println("keyTyped: " + e);[/color]
    int keyCode = e.getKeyCode();
    // etc

Observe the behaviour for each of the keys mentioned in that method. Read the KeyEvent API docs to see what events the keyTyped() method will find out about.

-----

You should observe standard Java coding conventions and give your class a descriptive name starting with an uppercase letter eg call it PongApplet rather than main.

Consider the more modern JApplet class and Swing technologies like timers etc.

[Edit] Slow... ;(

[Reskaillev]

You need to be more precise about "wasn't working". Is keyTyped() ever called? Add some debugging code (and remember to click in the applet window to give it focus)

@Override
public void keyTyped(KeyEvent e) {
    [color=green]System.out.println("keyTyped: " + e);[/color]
    int keyCode = e.getKeyCode();
    // etc

Observe the behaviour for each of the keys mentioned in that method. Read the KeyEvent API docs to see what events the keyTyped() method will find out about.

-----

You should observe standard Java coding conventions and give your class a descriptive name starting with an uppercase letter eg call it PongApplet rather than main.

Consider the more modern JApplet class and Swing technologies like timers etc.

[Edit] Slow... ;(

Thanks for answering! both of you! Its much appreciated

Well I tried the extra code (the console output) and it seems my arrowkeys (VK.UP and VK.DOWN and so on) don't respond to the keylistner...
When typing any other key it does respond properly ...

EDIT: to rule it out: yes my arrowkeys do work :p

[Norm]

Did you look at the definition of keytyped vs the other key events?

Also there are methods for getting the focus and for making a component focusable. Not all components can be in focus.