Curso - Programación de un Space Invaders en Java

1     package version10;
2     /**
3      * Curso Básico de desarrollo de Juegos en Java - Invaders
4      * 
5      * (c) 2004 Planetalia S.L. - Todos los derechos reservados. Prohibida su reproducción
6      * 
7      * http://www.planetalia.com
8      * 
9      */
10    
11    
12    import java.awt.Canvas;
13    import java.awt.Dimension;
14    import java.awt.Graphics;
15    import java.awt.event.WindowAdapter;
16    import java.awt.event.WindowEvent;
17    import java.awt.image.BufferedImage;
18    import java.net.URL;
19    import java.util.HashMap;
20    
21    import javax.imageio.ImageIO;
22    import javax.swing.JFrame;
23    import javax.swing.JPanel;
24    
25    public class Invaders extends Canvas {
26      public static final int WIDTH = 640;
27      public static final int HEIGHT = 480;
28      public static final int SPEED = 10;
29      
30      public HashMap sprites;
31      public int posX,posY,vX;

32      public BufferedImage buffer;

33      
34      public Invaders() {
35        sprites = new HashMap();
36        posX = WIDTH/2;
37        posY = HEIGHT/2;
38        vX = 2;

39        buffer = new BufferedImage(WIDTH,HEIGHT, BufferedImage.TYPE_INT_RGB);

40      
41        JFrame ventana = new JFrame("Invaders");
42        ventana.createBufferStrategy(2);
43        
44        
45        JPanel panel = (JPanel)ventana.getContentPane();
46        setBounds(0,0,WIDTH,HEIGHT);
47        panel.setPreferredSize(new Dimension(WIDTH,HEIGHT));
48        panel.setLayout(null);
49        panel.add(this);
50        ventana.setBounds(0,0,WIDTH,HEIGHT);
51        ventana.setVisible(true);
52        ventana.addWindowListener( new WindowAdapter() {
53          public void windowClosing(WindowEvent e) {
54            System.exit(0);
55          }
56        });
57        ventana.setIgnoreRepaint(true);
58        ventana.setResizable(false);
59      }
60      
61      public BufferedImage loadImage(String nombre) {
62        URL url=null;
63        try {
64          url = getClass().getClassLoader().getResource(nombre);
65          return ImageIO.read(url);
66        } catch (Exception e) {
67          System.out.println("No se pudo cargar la imagen " + nombre +" de "+url);
68          System.out.println("El error fue : "+e.getClass().getName()+" "+e.getMessage());
69          System.exit(0);
70          return null;
71        }
72      }
73      
74      public BufferedImage getSprite(String nombre) {
75        BufferedImage img = (BufferedImage)sprites.get(nombre);
76        if (img == null) {
77          img = loadImage("res/"+nombre);
78          sprites.put(nombre,img);
79        }

80        return img;
81      }
82      
83      public void paintWorld() {
84        Graphics g = buffer.getGraphics();
85        g.setColor(getBackground());
86        g.fillRect(0,0,getWidth(),getHeight());
87        g.drawImage(getSprite("bicho.gif"), posX, posY,this);
88      }
89      
90    
91      public void paint(Graphics g) {

92        g.drawImage(buffer,0,0,this);
93      }
94      
95      public void updateWorld() {
96        posX += vX;
97        if (posX < 0 || posX > WIDTH) vX = -vX;
98      }
99      
100     public void game() {
101       while (isVisible()) {
102         updateWorld();
103         paintWorld();
104         paint(getGraphics());
105         try { 
106            Thread.sleep(SPEED);
107         } catch (InterruptedException e) {}
108       }
109     }
110     
111     public static void main(String[] args) {
112       Invaders inv = new Invaders();
113       inv.game();
114     }
115   }
116