Jpanel Paint中的空指针异常

我在eclipse上制作了一个java游戏中的2D游戏，并且正在进行关卡设计。我在运行模式下获得以下运行时异常：Jpanel Paint中的空指针异常

`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._paintImmediately(Unknown Source) 
    at javax.swing.JComponent.paintImmediately(Unknown Source) 
    at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source) 
    at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source) 
    at javax.swing.RepaintManager.seqPaintDirtyRegions(Unknown Source) 
    at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(Unknown Source) 
    at java.awt.event.InvocationEvent.dispatch(Unknown Source) 
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source) 
    at java.awt.EventQueue.access$000(Unknown Source) 
    at java.awt.EventQueue$1.run(Unknown Source) 
    at java.awt.EventQueue$1.run(Unknown Source) 
    at java.security.AccessController.doPrivileged(Native Method) 
    at java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown Source) 
    at java.awt.EventQueue.dispatchEvent(Unknown Source) 
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source) 
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source) 
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source) 
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source) 
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source) 
    at java.awt.EventDispatchThread.run(Unknown Source) 
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException 
    at net.Pane.paint(Pane.java:30) 
    at javax.swing.JComponent.paintToOffscreen(Unknown Source) 
    at javax.swing.RepaintManager$PaintManager.paintDoubleBuffered(Unknown Source) 
    at javax.swing.RepaintManager$PaintManager.paint(Unknown Source) 
    at javax.swing.RepaintManager.paint(Unknown Source) 
    at javax.swing.JComponent._paintImmediately(Unknown Source) 
    at javax.swing.JComponent.paintImmediately(Unknown Source) 
    at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source) 
    at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source) 
    at javax.swing.RepaintManager.seqPaintDirtyRegions(Unknown Source) 
    at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(Unknown Source) 
    at java.awt.event.InvocationEvent.dispatch(Unknown Source) 
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source) 
    at java.awt.EventQueue.access$000(Unknown Source) 
    at java.awt.EventQueue$1.run(Unknown Source) 
    at java.awt.EventQueue$1.run(Unknown Source) 
    at java.security.AccessController.doPrivileged(Native Method) 
    at java.security.AccessControlContext$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) 
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException 
    at net.Pane.paint(Pane.java:30)`

依此类推。这是我的涂料方法：

`public void paint(Graphics g) { 
     super.paint(g); 
     Graphics2D g2d = (Graphics2D)g; 
     for(Block[] b : blocks) 
     { 
      for(Block bx : b) 
      { 
       //System.out.println(bx.letter); 
       g2d.drawImage(bx.bpic, bx.x*32, bx.y*32, this); 
      } 
     } 
     Toolkit.getDefaultToolkit().sync(); 
     g.dispose(); 
    }`

块被初始化成一个二维数组。哪里不对？

来源

2011-08-25 jbills

您需要添加堆栈跟踪。 – CoolBeans

您需要添加更多堆栈跟踪。你需要完成你的问题。 –

对不起。 – jbills

这种错误的发生，您忘了初始化一些组件如下

因之一。
您正尝试在尚未初始化的框架或面板上添加组件。

尝试通过卸下以下

super.paint（g）至执行该代码;
g.dispose（）;

来源

2012-05-13 20:29:36

最后不要拨打g.dispose();。您正在处理下次使用的图形对象。

由于该对象不是由您创建的，因此不需要处理它。

来源

2013-11-04 04:01:18 shuangwhywhy

Jpanel Paint中的空指针异常

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