KeyListener deja de funcionar

[Neoff224]

Código:

import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.Graphics;
import java.awt.Toolkit;
import java.awt.Image;

import java.util.Iterator;
import java.util.ArrayList;

import javax.swing.Timer;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;


/**
 * Write a description of class MenuInicial2 here.
 * 
 * @author (your name) 
 * @version (a version number or a date)
 */
public class Ventana extends JPanel implements ActionListener 
{   
    /*****************************
     * Declaration Variable Zone *
     *****************************/
    private int level = 0;
    private int counter = 0;
     
    /***************************
     * Declaration Object Zone *
     ***************************/
    Background background;
    Spacecraft spacecraft;
    ArrayList<MartianGroup1> martianGroup1;
    ArrayList<MartianGroup2> martianGroup2;
    ArrayList<MartianGroup3> martianGroup3;
    ArrayList<MartianGroup4> martianGroup4;
    
    /********************
     * Auxiliar Objects *
     ********************/
    Timer timer;
    
    public Ventana(int level)
    {
        this.level = level;
        addKeyListener(new KeyboardInterface());
        setFocusable(true);
        setDoubleBuffered(true);
        
        initializeMartianGroup1();
        initializeMartianGroup2();
        initializeMartianGroup3();
        initializeMartianGroup4();
        
        background = new Background();
        spacecraft = new Spacecraft();
        
        timer = new Timer(5, this);
        timer.start();
    }
    
    public void initializeMartianGroup1()
    {
        martianGroup1 = new ArrayList<MartianGroup1>();
        if (martianGroup1.isEmpty() == false)
        {
            martianGroup1.clear();
        }
        
        for (int position=0; position < 5; position++)
        {
            martianGroup1.add(position, new MartianGroup1(position));
        } 
    }
    
    public void paint (Graphics g)
    {
        super.paint(g);
        
        g.drawImage(background.getImage(), background.getX(), background.getY(), this);
        
        switch(counter)
        {
            case 0: paintGroup1(g); break;
            case 1: paintGroup2(g); break;
            case 2: paintGroup3(g); break;
            case 3: paintGroup4(g); break;
            default: break;
        }
        
        paintShots(g);
        
        g.drawImage(spacecraft.getImage(), spacecraft.getX(), spacecraft.getY(), this);
        Toolkit.getDefaultToolkit().sync();
        g.dispose();
    }
    
    public void actionPerformed(ActionEvent e)
    {
        switch(counter)
        {
            case 0: moveGroup1(); checkCollisionsGroup1(); break;
            case 1: moveGroup2(); checkCollisionsGroup2(); break;
            case 2: moveGroup3(); checkCollisionsGroup3(); break;
            case 3: moveGroup4(); checkCollisionsGroup4(); break;
            default: break;
        }
        
        ArrayList<Shot> activeShots = spacecraft.getShots();
        
        for (int i = 0; i < activeShots.size(); i++)
        {
            Shot shot = activeShots.get(i);
            if (shot.esVisible())
            {
                shot.move();
            }
            else { activeShots.remove(i); }
        }
        
        spacecraft.move();
        repaint();
    }
    
    public void paintGroup1(Graphics g)
    {
        MartianGroup1 martianInUse;
        Iterator<MartianGroup1> martianIterator  = martianGroup1.iterator();
        while(martianIterator.hasNext())
        {
            martianInUse = martianIterator.next();
            if (martianInUse.getVisible() == true)
            {
                g.drawImage(martianInUse.getImage(), martianInUse.getX(), martianInUse.getY(), this);
            }
        }
    }
    
    public void paintShots(Graphics g)
    {
        ArrayList<Shot> activeShots = spacecraft.getShots();
        
        for (int i = 0; i < activeShots.size(); i++)
        {
            Shot shot = activeShots.get(i);
            if (shot.esVisible())
            {
                g.drawImage(shot.getImage(), shot.getX(), shot.getY(), this);
            }
        }
    }
    
    public void moveGroup1() 
    {
        int martianCounter = 0;
        boolean visible = false;
        MartianGroup1 martianInUse;
        Iterator<MartianGroup1> martianIterator  = martianGroup1.iterator();
        while(martianIterator.hasNext())
        {
            martianInUse = martianIterator.next();
            martianInUse.move(martianCounter);
            if (martianIterator.hasNext() == false && martianInUse.getX() == (-60))
            {
                int position = 0;
                Iterator<MartianGroup1> martianIterator2  = martianGroup1.iterator();
                while(martianIterator2.hasNext())
                {
                    martianIterator2.next().restart(position);
                    position++;
                }
                counter++;
            }
            if (martianInUse.getVisible()) { visible = true; }
            martianCounter++;
        }
        if (!visible) { counter++; }
    }
    
    public void checkCollisionsGroup1()
    {
        Rectangle r3 = spacecraft.getBounds();
        
        for (int i = 0; i < martianGroup1.size(); i++)
        {
            Rectangle r2 = martianGroup1.get(i).getBounds();
            
            if (r3.intersects(r2))
            {
                spacecraft.setVisible(false);
            }
        }
        
        ArrayList<Shot> activeShots = spacecraft.getShots();
        
        for (int j = 0; j < activeShots.size(); j++)
        {
            Shot shot = activeShots.get(j);
            
            Rectangle r1 = shot.getBounds();
            for (int i = 0; i < martianGroup1.size(); i++)
            {
                if(martianGroup1.get(i).getVisible())
                {
                    Rectangle r2 = martianGroup1.get(i).getBounds();
                    
                    if (r1.intersects(r2))
                    {
                        shot.setVisible(false);
                        martianGroup1.get(i).setVisible(false);
                    }
                }
            }
        }
    }
    
    public class KeyboardInterface extends KeyAdapter
    {        
        public void keyPressed(KeyEvent e)
        {
            spacecraft.keyPressed(e);
        }
        
        public void keyReleased(KeyEvent e)
        {
            spacecraft.keyReleased(e);
        }
    }
}