基于 Tiem 更新 JTable

Question

I am using a JTable to display values produced by a long running process and I want the appearance to change as values "age out". There is a timestamp indicating the last time each row of data changed and I want to display this in a different format when it is more than a minute (or an hour) old.

I might change the background color for active rows but I have not worked on that yet.

Relevant sections of my code are below. I call repaint, and I've tried calling fireTableDataChanged without any luck. The older values never change to the "inactive" format. If I quit and restart, the older values get drawn with the inactive format but it does not happen dynamically.

private final long startup = System.currentTimeMillis ();

private static long minuteMillis = 1000 * 60;

private final SimpleDateFormat inactiveFormat = new SimpleDateFormat ("HH:mm");

private final SimpleDateFormat currentFormat = new SimpleDateFormat ("HH:mm:ss");

private long timestamp = 0; // Obtained from data

// Part of the table model
@Override // Subclass of DefaultTableModel
public Object getValueAt (int row, int column)
{
    if (timestamp < startup - minuteMillis)
    {
        return inactiveFormat.format (timestamp);
    }
    return currentFormat.format (timestamp);
}

final Thread thread = new Thread ()
{
    @Override
    public void run ()
    {
        while (true)
        {
            try
            {
                Thread.sleep (100);
                timestamp = readFromFile(); // Read from elsewhere
                // model.fireTableDataChanged (); // Does not help
                table.repaint (); // Does not update older values
            }
            catch (final Throwable e)
            {
                e.printStackTrace ();
            }
        }
    }
};
thread.start ();

Answer 1

I found the problem. The variable 'startup' in the code above should be System.currentTimeMillis(). Here is a working demo in case anyone else wants to do something similar. I think it is fun.

package demo;

import java.io.File;
import java.text.SimpleDateFormat;

import javax.swing.*;
import javax.swing.table.DefaultTableModel;

import org.apache.logging.log4j.*;

public class TableDemo extends JPanel
{
    private final Logger logger = LogManager.getFormatterLogger (this.getClass ());

    public static void main (String[] args)
    {
        final TableDemo app = new TableDemo ();
        app.execute ();
        app.cycle ();
    }

    private final SimpleDateFormat inactiveFormat = new SimpleDateFormat ("HH:mm");

    private final SimpleDateFormat activeFormat = new SimpleDateFormat ("HH:mm:ss");

    /** Timestamp of learning data. */
    private final Long[][] timestamp = {{0l, 0l, 0l}, {0l, 0l, 0l}};

    private static long minuteMillis = 1000 * 10; // Reduced for testing

    /**
     * Create table model with data
     *
     * @see https://www.codejava.net/java-se/swing/a-simple-jtable-example-for-display
     */
    private final DefaultTableModel model = new DefaultTableModel ()
    {
        @Override
        public int getColumnCount ()
        {
            return timestamp[0].length;
        }

        @Override
        public int getRowCount ()
        {
            return timestamp.length;
        }

        @Override
        public Object getValueAt (int row, int column)
        {
            String result = "-";
            if (row < timestamp.length)
            {
                if (column < timestamp[0].length)
                {
                    final long value = timestamp[row][column];
                    if (value < System.currentTimeMillis () - minuteMillis)
                    {
                        result = inactiveFormat.format (value);
                    }
                    else
                    {
                        result = activeFormat.format (value);
                    }
                }
            }
            return result;
        }
    };

    private final JTable table = new JTable (model);

    private final JFrame frame = new JFrame ("Demo");

    public TableDemo ()
    {
        frame.setContentPane (new JScrollPane (table));
        frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
    }

    public void execute ()
    {
        frame.pack ();
        frame.setVisible (true);
    }

    public void cycle ()
    {
        final Thread thread = new Thread ()
        {
            @Override
            public void run ()
            {
                // Make it easy to cd to the right place
                logger.info (new File ("data.txt").getAbsolutePath ());
                while (true)
                {
                    try
                    {
                        Thread.sleep (1000);
                        for (int i = 0; i < table.getRowCount (); i++)
                        {
                            // From bash:
                            // > touch data10.txt ; touch data02.txt
                            for (int j = 0; j < table.getColumnCount (); j++)
                            {
                                final String filename = String.format ("data%d%d.txt", i, j);
                                final File file = new File (filename);
                                if (file.exists ())
                                {
                                    timestamp[i][j] = file.lastModified ();
                                }
                                else
                                {
                                    timestamp[i][j] = 0L;
                                }
                            }
                        }
                        table.repaint ();
                    }
                    catch (final Throwable e)
                    {
                        e.printStackTrace ();
                    }
                }
            }
        };
        thread.start ();
    }
}