關於Swing JTable的getColumnClass

 今天在測試如下代碼時，總是會報錯。

jTable0.setModel(new DefaultTableModel(new Object[][] {<br />{ "0x0", 0, }, { "1x0", 0, }, }, new String[] { "string",<br />"int", }) {<br />private static final long serialVersionUID = 1L;<br />Class<?>[] types = new Class<?>[] { Object.class, int.class, };</p><p>@Override<br />public Class<?> getColumnClass(int columnIndex) {<br />return types[columnIndex];<br />}<br />});

報錯資訊如下：

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException<br />at javax.swing.JTable.prepareRenderer(JTable.java:5729)<br />at javax.swing.plaf.basic.BasicTableUI.paintCell(BasicTableUI.java:2075)<br />at javax.swing.plaf.basic.BasicTableUI.paintCells(BasicTableUI.java:1977)<br />at javax.swing.plaf.basic.BasicTableUI.paint(BasicTableUI.java:1773)<br />at javax.swing.plaf.ComponentUI.update(ComponentUI.java:143)<br />at javax.swing.JComponent.paintComponent(JComponent.java:763)<br />at javax.swing.JComponent.paint(JComponent.java:1027)<br />at javax.swing.JComponent.paintChildren(JComponent.java:864)<br />at javax.swing.JComponent.paint(JComponent.java:1036)<br />at javax.swing.JViewport.paint(JViewport.java:747)<br />at javax.swing.JComponent.paintChildren(JComponent.java:864)<br />at javax.swing.JComponent.paint(JComponent.java:1036)<br />at javax.swing.JComponent.paintChildren(JComponent.java:864)<br />at javax.swing.JComponent.paint(JComponent.java:1036)<br />at javax.swing.JComponent.paintChildren(JComponent.java:864)<br />at javax.swing.JComponent.paint(JComponent.java:1036)<br />at javax.swing.JLayeredPane.paint(JLayeredPane.java:564)<br />at javax.swing.JComponent.paintChildren(JComponent.java:864)<br />at javax.swing.JComponent.paintToOffscreen(JComponent.java:5129)<br />at javax.swing.BufferStrategyPaintManager.paint(BufferStrategyPaintManager.java:277)<br />at javax.swing.RepaintManager.paint(RepaintManager.java:1217)<br />at javax.swing.JComponent.paint(JComponent.java:1013)<br />at java.awt.GraphicsCallback$PaintCallback.run(GraphicsCallback.java:21)<br />at sun.awt.SunGraphicsCallback.runOneComponent(SunGraphicsCallback.java:60)<br />at sun.awt.SunGraphicsCallback.runComponents(SunGraphicsCallback.java:97)<br />at java.awt.Container.paint(Container.java:1780)<br />at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:814)<br />at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:714)<br />at javax.swing.RepaintManager.seqPaintDirtyRegions(RepaintManager.java:694)<br />at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(SystemEventQueueUtilities.java:128)<br />at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)<br />at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)<br />at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)<br />at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)<br />at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)<br />at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)<br />at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)<br />at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

報錯資訊中似乎看不出什麼。

  最後經過多次的測試才發現，當將JTable的某一列的類型設定為基礎資料型別 (Elementary Data Type)的時候，就會產生這個錯誤，而設定為對應的封裝類則沒有這種情況，不清楚是什麼原因。

  上面代碼稍做改動即可測試通過：

jTable0.setModel(new DefaultTableModel(new Object[][] {<br />{ "0x0", 0, }, { "1x0", 0, }, }, new String[] { "string",<br />"int", }) {<br />private static final long serialVersionUID = 1L;<br />Class<?>[] types = new Class<?>[] { Object.class, Integer.class, };</p><p>@Override<br />public Class<?> getColumnClass(int columnIndex) {<br />return types[columnIndex];<br />}<br />});