java – 对JTable进行排序会导致NullPointerException
内容导读
互联网集市收集整理的这篇技术教程文章主要介绍了java – 对JTable进行排序会导致NullPointerException，小编现在分享给大家，供广大互联网技能从业者学习和参考。文章包含4969字，纯文字阅读大概需要8分钟。
内容图文
我有一个JTable,当点击相应的按钮时,它开始填充在后台继续的文件树步行的结果.这很好用.
然后我决定要对表进行排序.经过一些阅读后,我创建了一个TableRowSorter并设置表来使用它.它似乎工作,但仔细检查后,我注意到几个文件结果不存在.我禁用了分拣机并再次运行程序并且所有文件都存在,再次重新启用分拣机时有些遗漏,但每次丢弃时似乎都是不同的文件.
为了检查这一点,我创建了一个自包含的代码块作为测试(见下文),它代表了JTable代码(事实上,大块直接从现有程序代码中提取).文件树遍历由for循环表示.再次,没有分拣机它完美地工作.但是,当我启用分拣机时(通过取消注释第29行)整个程序冻结,我被告知有一个NullPointerException.
我不知道造成这些问题的原因是什么,事实上它们甚至是相关的.欢迎任何有关错误的想法.
import javax.swing.table.*;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.util.*;
public class Sort extends JFrame{
private JTable table;
private DefaultTableModel model;
private TableRowSorter<DefaultTableModel> sorter;
private JButton go;
public Sort(){
super("Sort");
// Create table and model
model = new DefaultTableModel(0, 4);
table = new JTable(model);
// Setup sorting
sorter = new TableRowSorter<DefaultTableModel>(model);
ArrayList<RowSorter.SortKey> sortKeys = new ArrayList<RowSorter.SortKey>();
sortKeys.add(new RowSorter.SortKey(2, SortOrder.ASCENDING));
sortKeys.add(new RowSorter.SortKey(3, SortOrder.ASCENDING));
sortKeys.add(new RowSorter.SortKey(0, SortOrder.ASCENDING));
sorter.setSortKeys(sortKeys);
//table.setRowSorter(sorter);
// Create Scroll Pane
JScrollPane tableScroller = new JScrollPane(table);
table.setFillsViewportHeight(true);
tableScroller.setPreferredSize(new Dimension(500, 200));
// Setup button
go = new JButton("Go");
go.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
SwingWorker<Void, Void> worker = new SwingWorker<Void, Void>(){
public Void doInBackground(){
for(int i = 0; i < 200; i++){
model.addRow( new Object[] { (new Integer(i)), String.valueOf(i), String.valueOf(i%50), String.valueOf(i%10) } );
}
return null;
}
};
worker.execute();
}
});
// Assemble GUI
JPanel panel = new JPanel(new BorderLayout());
panel.add(tableScroller, BorderLayout.CENTER);
panel.add(go, BorderLayout.SOUTH);
setContentPane(panel);
setDefaultCloseOperation(EXIT_ON_CLOSE);
pack();
setVisible(true);
}
public static void main(String[] args){
SwingUtilities.invokeLater(new Runnable(){
public void run(){
new Sort();
}
});
}
}
堆栈跟踪
这是堆栈跟踪的一部分,它重复..
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.DefaultRowSorter.convertRowIndexToModel(DefaultRowSorter.java:518)
at javax.swing.JTable.convertRowIndexToModel(JTable.java:2645)
at javax.swing.JTable.getValueAt(JTable.java:2720)
at javax.swing.JTable.prepareRenderer(JTable.java:5718)
at javax.swing.plaf.basic.BasicTableUI.paintCell(BasicTableUI.java:2114)
at javax.swing.plaf.basic.BasicTableUI.paintCells(BasicTableUI.java:2016)
at javax.swing.plaf.basic.BasicTableUI.paint(BasicTableUI.java:1812)
at javax.swing.plaf.ComponentUI.update(ComponentUI.java:161)
at javax.swing.JComponent.paintComponent(JComponent.java:778)
at javax.swing.JComponent.paint(JComponent.java:1054)
at javax.swing.JComponent.paintToOffscreen(JComponent.java:5221)
at javax.swing.BufferStrategyPaintManager.paint(BufferStrategyPaintManager.java:295)
at javax.swing.RepaintManager.paint(RepaintManager.java:1206)
at javax.swing.JComponent._paintImmediately(JComponent.java:5169)
at javax.swing.JComponent.paintImmediately(JComponent.java:4980)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:770)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:728)
at javax.swing.RepaintManager.prePaintDirtyRegions(RepaintManager.java:677)
at javax.swing.RepaintManager.access$700(RepaintManager.java:59)
at javax.swing.RepaintManager$ProcessingRunnable.run(RepaintManager.java:1621)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:705)
at java.awt.EventQueue.access$000(EventQueue.java:101)
at java.awt.EventQueue$3.run(EventQueue.java:666)
at java.awt.EventQueue$3.run(EventQueue.java:664)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:675)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:211)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:128)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:117)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:113)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
...
解决方法:
你的代码有一个很大的问题,可以解释你所观察到的：你正在EDT之外修改你的表模型,这是邪恶的.
由于您使用的是SwingWorker,因此应该尝试完全正确使用它,例如使用其发布API来调用model.addRow().
内容总结
以上是互联网集市为您收集整理的java – 对JTable进行排序会导致NullPointerException全部内容，希望文章能够帮你解决java – 对JTable进行排序会导致NullPointerException所遇到的程序开发问题。 如果觉得互联网集市技术教程内容还不错，欢迎将互联网集市网站推荐给程序员好友。
内容备注
版权声明：本文内容由互联网用户自发贡献，该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务，不拥有所有权，不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容， 请发送邮件至 gblab@vip.qq.com 举报，一经查实，本站将立刻删除。
内容手机端
扫描二维码推送至手机访问。