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我正在尝试从数据库中获取记录的特定值我使用 AbstractTableModel 在 swings 中创建运行时 JTable 但我试图从该类中的不同 javaclass 触发查询。我为 where 子句提供条件但我无法显示该记录在其他 JFrame .AbstractTableModel 工作正常,因为我能够在我实际声明表的 internalFrame 中检索数据。我可以将 JInternalFrame 中的数据检索到 JFrame 我正在尝试使用 getParent.add() 方法但是它会抛出 nullpointerExceptionException in thread "AWT-EventQueue-0" java.lang.NullPointerException at secondproject.select_particular_field$1.actionPerformed(select_particular_field.java:84) at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995) at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318) at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387) at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242) at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236) at java.awt.Component.processMouseEvent(Component.java:6038) at javax.swing.JComponent.processMouseEvent(JComponent.java:3260) at java.awt.Component.processEvent(Component.java:5803) at java.awt.Container.processEvent(Container.java:2058) at java.awt.Component.dispatchEventImpl(Component.java:4410) at java.awt.Container.dispatchEventImpl(Container.java:2116) at java.awt.Component.dispatchEvent(Component.java:4240) at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4322) at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3986) at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3916) at java.awt.Container.dispatchEventImpl(Container.java:2102) at java.awt.Window.dispatchEventImpl(Window.java:2429) at java.awt.Component.dispatchEvent(Component.java:4240) at java.awt.EventQueue.dispatchEvent(EventQueue.java:599) at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273) at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160) at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)

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这有点含糊,但通常会抛出 NPE,因为您在对象不存在时调用方法。在这种情况下,它似乎发生在您单击按钮时select_particular_field.java

但我正在尝试从该类的不同 javaclass 中触发查询

也许这就是问题所在。在不同的类中,对象不存在/尚未创建。

希望它有帮助

于 2012-03-26T12:21:05.463 回答