带线程的Java Swing-repaint和两个for循环给出错误，没有任何提示

我有一个小java程序，它有一个二维int数组：私有int[][]块网格； 我想在重绘函数（作为线程定期调用）中用两个for循环捕捉数组的值

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有人能帮我吗？

检查数组

区块网格

是否已初始化，是否在drawStar方法的范围内。

drawStar

方法中存在空指针异常。

---

检查可能指向null的调用方的方法，并确保捕获它们（使用

try

/

catch

或在调用之前使用

如果（x！=null）

，

检查数组

blockGrid

是否已初始化且在drawStar方法的范围内。

drawStar

方法中存在空指针异常。

---

检查可能指向null的调用方的方法并确保捕获它们（使用

try

/

catch

或在调用之前使用

如果（x！=null）

）

您确定这是完整的堆栈跟踪吗？我刚刚添加了一些错误消息行。行268是我上面提到的行：System.out.print（blockGrid[（ix）][（iy）]+“| |”）；（它没有语法错误……因此我假设它与循环的线程处理有关？显然，我是新手）谢谢-我有点明白了-我确实理解is与数组的定义有关，数组不知何故不指向内存地址。但在前一行中，完全相同的代码正在工作（这意味着数组指向内存位置IMHO）.我还定义了数组，每个元素上有0，有两个for循环：int[][]blockGrid=new int[21][19]；for（int ix=0；ixIt现在可以工作了-我将定义公开为public static public static int[][]blockGrid=new int[21][19]；TY谢谢你的帮助！！你确定这是完整的堆栈跟踪吗？我刚刚添加了更多的错误消息行。行268就是我上面提到的行：System.out.print（blockGrid[（ix）][（iy）]+“| |”）；（它没有语法错误…所以我假设它与循环的线程处理有关？显然，我是新手）谢谢-我有点明白了-我确实理解is与数组的定义有关，数组不知何故不指向内存地址。但在前一行中，完全相同的代码正在工作（这意味着数组指向内存位置IMHO）。我还使用两个for循环定义了每个元素上都有0的数组：int[][]blockGrid=new int[21][19]；for（int ix=0；ixIt现在可以工作了-我将定义公开为static public static int[][]blockGrid=new int[21][19]；TY以获得您的帮助！！它现在可以工作了-我将定义公开为static public static int[]blockGrid=new int[21][19]；谢谢你的帮助！！没问题，只要看看你的代码，确保将blockGrid设置为静态是合理的，而不是以某种方式传递它现在就可以了-我将定义公开为static public static int[][]blockGrid=new int[21][19]；TY感谢您的帮助！！没问题，只需查看您的代码，确保将blockGrid设置为静态并以某种方式传递它是合理的

@Override
public void paintComponent(Graphics g) {
    super.paintComponent(g);

    drawthings(g);
}

private void drawthings(Graphics g) {


    for(int ix=0;ix<20;ix++)
    {
        for(int iy=0;iy<18;iy++)
        {
            System.out.print( blockGrid[(ix)][(iy)] + " ||");
        }
    }

    at java.desktop/javax.swing.RepaintManager$4.run(RepaintManager.java:848)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
    at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
    at java.desktop/javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:848)
    at java.desktop/javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:823)
    at java.desktop/javax.swing.RepaintManager.prePaintDirtyRegions(RepaintManager.java:772)
    at java.desktop/javax.swing.RepaintManager$ProcessingRunnable.run(RepaintManager.java:1884)
    at java.desktop/java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:313)
    at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:770)
    at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
    at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
    at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
    at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:740)
    at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
    at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
    at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
    at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
    at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at iota_cafe3.Board.drawStar(Board.java:268)
    at iota_cafe3.Board.paintComponent(Board.java:255)
    at java.desktop/javax.swing.JComponent.paint(JComponent.java:1074)
    at java.desktop/javax.swing.JComponent.paintToOffscreen(JComponent.java:5255)
    at java.desktop/javax.swing.RepaintManager$PaintManager.paintDoubleBufferedImpl(RepaintManager.java:1643)
    at java.desktop/javax.swing.RepaintManager$PaintManager.paintDoubleBuffered(RepaintManager.java:1618)
    at java.desktop/javax.swing.RepaintManager$PaintManager.paint(RepaintManager.java:1556)
    at java.desktop/javax.swing.RepaintManager.paint(RepaintManager.java:1323)
    at java.desktop/javax.swing.JComponent._paintImmediately(JComponent.java:5203)
    at java.desktop/javax.swing.JComponent.paintImmediately(JComponent.java:5013)
    at java.desktop/javax.swing.RepaintManager$4.run(RepaintManager.java:865)
    at java.desktop/javax.swing.RepaintManager$4.run(RepaintManager.java:848)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
    at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
    at java.desktop/javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:848)
    at java.desktop/javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:823)
    at java.desktop/javax.swing.RepaintManager.prePaintDirtyRegions(RepaintManager.java:772)
    at java.desktop/javax.swing.RepaintManager$ProcessingRunnable.run(RepaintManager.java:1884)
    at java.desktop/java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:313)
    at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:770)
    at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
    at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
    at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
    at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:740)
    at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
    at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
    at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
    at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
    at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at iota_cafe3.Board.drawStar(Board.java:268)
    at iota_cafe3.Board.paintComponent(Board.java:255)
    at java.desktop/javax.swing.JComponent.paint(JComponent.java:1074)
    at java.desktop/javax.swing.JComponent.paintToOffscreen(JComponent.java:5255)
    at java.desktop/javax.swing.RepaintManager$PaintManager.paintDoubleBufferedImpl(RepaintManager.java:1643)
    at java.desktop/javax.swing.RepaintManager$PaintManager.paintDoubleBuffered(RepaintManager.java:1618)
    at java.desktop/javax.swing.RepaintManager$PaintManager.paint(RepaintManager.java:1556)
    at java.desktop/javax.swing.RepaintManager.paint(RepaintManager.java:1323)
    at java.desktop/javax.swing.JComponent._paintImmediately(JComponent.java:5203)
    at java.desktop/javax.swing.JComponent.paintImmediately(JComponent.java:5013)
    at java.desktop/javax.swing.RepaintManager$4.run(RepaintManager.java:865)
    at java.desktop/javax.swing.RepaintManager$4.run(RepaintManager.java:848)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
    at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
    at java.desktop/javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:848)
    at java.desktop/javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:823)
    at java.desktop/javax.swing.RepaintManager.prePaintDirtyRegions(RepaintManager.java:772)
    at java.desktop/javax.swing.RepaintManager$ProcessingRunnable.run(RepaintManager.java:1884)
    at java.desktop/java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:313)
    at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:770)
    at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
    at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
    at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
    at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:740)
    at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
    at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
    at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
    at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
    at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)