Move sprite using keyboard

Question

Hi. I am trying to make a simple game where you move a tank around. My problem is that I can't seem to get it to move right.
Here is the code:
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.AffineTransform;
public class JavaGame extends Applet implements KeyListener{
  private Image martin;
  Point pos = new Point(200,200);
  double angle = 0.00;
  double vel = 0;
  public void init() {
    setBackground(Color.white);
    addKeyListener(this);
    martin = getImage(getDocumentBase(),"tank.gif");
  public void paint(Graphics g) {
      Graphics2D g2d = (Graphics2D) g;
             AffineTransform tx = new AffineTransform();
             double scalex = 1;
             double scaley = 1;
             tx.scale(scalex, scaley);
             double x = pos.x;
             double y = pos.y;
             double dx = Math.sin(angle)*vel;
             double dy = -Math.cos(angle)*vel;
             pos.x+=dx;
             pos.y+=dy;
             tx.translate(pos.x, pos.y);
             tx.rotate(angle,16,16);
            g2d.drawImage(martin, tx, this);
  public void keyPressed(KeyEvent e) {
      if (e.getKeyCode() == KeyEvent.VK_UP)   vel = 2;
      else if (e.getKeyCode() == KeyEvent.VK_DOWN) vel = -2;
      else if (e.getKeyCode() == KeyEvent.VK_LEFT) angle -= 0.02;
      else if (e.getKeyCode() == KeyEvent.VK_RIGHT) angle += 0.02;
      repaint();
  public void keyReleased(KeyEvent e) {}
  public void keyTyped(KeyEvent e)    {}
}Any help appreciated

Answer 1

Hehe... Sounds simple enough. I could do that if I could understand why my sprites rotate angle changes after driving forward or backward (see the example at http://www.harme.dk/tank). When the "game" starts and you press left or right, the tank rotates correct, but after you push up, and move the tank, the rotate doesn't work anymore.
I would think it have something to do with either my math, or the transform method?