While循環導致異常？

我想要動畫一個精靈。有一個包含玩家對象的主類。這個播放器對象擴展了一個精靈對象。玩家對象將它的圖像數組賦給精靈類，這應該在不同的圖像之間切換。但現在，每當我試圖用while（）寫東西時，我得到一個異常？一切工作正常，但我不能得到任何while循環開始......While循環導致異常？

遊戲類繪製圖像：

g2d.drawImage(player.getImage(),(int) player.getX(),(int) player.getY(), null);

播放器擴展了Sprite類。這包含x和y座標。

public Player(double x, double y) { 
    bitmap = new Bitmap("/sprites.png"); 
    sprites = new BufferedImage[2]; 
    sprites[0] = bitmap.getSprite(2, 2, 48, 48); 
    sprites[1] = bitmap.getSprite(52, 2, 48, 48); 
    this.x = x; 
    this.y = y; 
    setImages(sprites); 
}

這就是玩家類的構造函數。

但是，爲什麼我不能使用while循環？

你需要更多的代碼嗎？

這裏是我的例外

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException 
at com.ochs.game.Game.paint(Game.java:59) 
at javax.swing.JComponent.paintChildren(Unknown Source) 
at javax.swing.JComponent.paint(Unknown Source) 
at javax.swing.JComponent.paintChildren(Unknown Source) 
at javax.swing.JComponent.paint(Unknown Source) 
at javax.swing.JLayeredPane.paint(Unknown Source) 
at javax.swing.JComponent.paintChildren(Unknown Source) 
at javax.swing.JComponent.paintToOffscreen(Unknown Source) 
at javax.swing.RepaintManager$PaintManager.paintDoubleBuffered(Unknown Source) 
at javax.swing.RepaintManager$PaintManager.paint(Unknown Source) 
at javax.swing.RepaintManager.paint(Unknown Source) 
at javax.swing.JComponent.paint(Unknown Source) 
at java.awt.GraphicsCallback$PaintCallback.run(Unknown Source) 
at sun.awt.SunGraphicsCallback.runOneComponent(Unknown Source) 
at sun.awt.SunGraphicsCallback.runComponents(Unknown Source) 
at java.awt.Container.paint(Unknown Source) 
at java.awt.Window.paint(Unknown Source) 
at javax.swing.RepaintManager$3.run(Unknown Source) 
at javax.swing.RepaintManager$3.run(Unknown Source) 
at java.security.AccessController.doPrivileged(Native Method) 
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source) 
at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source) 
at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source) 
at javax.swing.RepaintManager.prePaintDirtyRegions(Unknown Source) 
at javax.swing.RepaintManager.access$1000(Unknown Source) 
at javax.swing.RepaintManager$ProcessingRunnable.run(Unknown Source) 
at java.awt.event.InvocationEvent.dispatch(Unknown Source) 
at java.awt.EventQueue.dispatchEventImpl(Unknown Source) 
at java.awt.EventQueue.access$200(Unknown Source) 
at java.awt.EventQueue$3.run(Unknown Source) 
at java.awt.EventQueue$3.run(Unknown Source) 
at java.security.AccessController.doPrivileged(Native Method) 
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source) 
at java.awt.EventQueue.dispatchEvent(Unknown Source) 
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source) 
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source) 
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source) 
at java.awt.EventDispatchThread.pumpEvents(Unknown Source) 
at java.awt.EventDispatchThread.pumpEvents(Unknown Source) 
at java.awt.EventDispatchThread.run(Unknown Source)

這裏的game.java代碼：

public class Game extends JPanel implements Runnable{ 

public static final int WIDTH = 320; 
public static final int HEIGHT = 240; 
public static final int SCALE = 2; 

public boolean isRunning; 

private Player player; 

public Game() { 
    start(); 
} 

public void start() { 
    isRunning = true; 
    new Thread(this).start(); 
} 

public void stop() { 
    isRunning = false; 
} 

public void run() { 
    init(); 
    while(isRunning) { 

     update(); 
     repaint(); 

     try { 
      Thread.sleep(5); 
     } catch (InterruptedException e) { 
      System.out.println("Failed to sleep"); 
     } 
    } 
} 

public void init() { 
    player = new Player(100, 100); 
} 

public void update() { 

} 

public void paint(Graphics g) { 
    super.paint(g); 
    Graphics2D g2d = (Graphics2D)g; 
    g2d.drawImage(player.getImage(),(int) player.getX(),(int) player.getY(), null); 
} 

public static void main(String[] args) { 
    Game gameComponent = new Game(); 
    Dimension size = new Dimension(WIDTH*SCALE, HEIGHT*SCALE); 

    JFrame frame = new JFrame("Invaders"); 
    frame.setVisible(true); 
    frame.setSize(size); 
    frame.setLocationRelativeTo(null); 
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
    frame.setResizable(false); 
    frame.add(gameComponent); 
} 
}

來源

2013-08-18 user2410644

粘貼Game.Java代碼。 –

將game.java代碼添加到問題 – user2410644

什麼是59行？ – Pavlos