java - JTable 中的日期排序无效

Question

请看下面的代码

import java.awt.*;
import java.awt.event.*;
import java.text.NumberFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.*;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.*;
import javax.swing.table.*;

public class TableBasic extends JFrame
{
    public TableBasic()
    {

        String[] columnNames = {"Date", "String", "Long", "Boolean"};
        Object[][] data =
        {
            {getJavaDate("13-11-2020"), "A", new Long(1), Boolean.TRUE },
            {getJavaDate("13-11-2018"), "B", new Long(2), Boolean.FALSE},
            {getJavaDate("12-11-2015"), "C", new Long(9), Boolean.TRUE },
            {getJavaDate("12-11-2015"), "D", new Long(4), Boolean.FALSE}
        };

        final JTable table = new JTable(data, columnNames);
        table.setPreferredScrollableViewportSize(table.getPreferredSize());
        table.setAutoCreateRowSorter(true);
        table.getColumnModel().getColumn(0).setCellRenderer(tableCellRenderer);

        // DefaultRowSorter has the sort() method
        DefaultRowSorter sorter = ((DefaultRowSorter)table.getRowSorter()); 
        ArrayList list = new ArrayList();
        list.add( new RowSorter.SortKey(0, SortOrder.DESCENDING) );
        sorter.setSortKeys(list);
        sorter.sort();

        JScrollPane scrollPane = new JScrollPane( table );
        getContentPane().add( scrollPane );
    }

    private TableCellRenderer tableCellRenderer = new DefaultTableCellRenderer() 
    {

        SimpleDateFormat f = new SimpleDateFormat("dd-MM-yyyy");

        public Component getTableCellRendererComponent(JTable table,Object value, boolean isSelected, boolean hasFocus,int row, int column) 
        {
            if( value instanceof Date) 
            {
                value = f.format(value);
            }
            return super.getTableCellRendererComponent(table, value, isSelected,hasFocus, row, column);
        }
    };

    private Date getJavaDate(String s)
    {
        try {
            SimpleDateFormat sdf = new SimpleDateFormat("dd-MM-yyyy");
            Date d = sdf.parse(s);
             return d;

        } catch (ParseException ex) {
            Logger.getLogger(TableBasic.class.getName()).log(Level.SEVERE, null, ex);
            return null;
        }
    }



    public static void main(String[] args)
    {
        TableBasic frame = new TableBasic();
        frame.setDefaultCloseOperation( EXIT_ON_CLOSE );
        frame.pack();
        frame.setLocationRelativeTo( null );
        frame.setVisible(true);
    }
}

现在，只需尝试使用 Date 字段对其进行排序。它以无效的方式对其进行排序!下面是结果!

为什么会这样？我什至用过 cell render!

Answer 1

表格不知道该列总是包含 Date 实例，因此它必须按时间顺序排序，除非您通过覆盖表格模型的 getColumnClass() 方法给它该信息:

final Class<?>[] columnClasses = new Class<?>[] {Date.class, String.class, Long.class, Boolean.class};

DefaultTableModel model = new DefaultTableModel(...) {
    @Override
    public Class<?> getColumnClass(int column) {
        return columnClasses[column];
    }
});
JTable table = new JTable(model);

额外的好处:数字和 boolean 列将自动呈现并正确排序。