Question

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。

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了，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，大块直接从现有的程序代码中取出）。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。任何有关错误的想法都是受欢迎的。

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
    ...

Answer 1

你的代码有一个很大的问题，可以解释你所观察到的内容：你正在修改你的桌面模型在外面 EDT，这是邪恶的。

由于您使用的是SwingWorker，因此您应该尝试完全正确使用它，例如使用其publish API来调用model.addRow()。

对JTable进行排序会导致NullPointerException

堆栈跟踪

1 个答案: