自动更新JTable

Question

I am creating a Jtable from .txt file. The .txt file keeps on updating over a certain period of time. I need to know if there are any ways to reflect those changes in .txt file in my Jtable AT RUN-TIME!!! I know on restarting, the table reads .txt file but is there any way to do it on run time??

Answer 1

您应该编写一个后台线程，该线程继续检查文本文件的内容并不断更新表模型。

Answer 2

I'd imagine to might look something like this...

public class BackgroundMonitor implements Runnable {

    public void run() {

        while (true) {
            // Check to see if the file has changed since the last update...
            // If it has you will want to store the metrics and return true...
            if (hasChanged()) {

                // Load the contents into what ever construct you need to use
                ... = loadContents();

                // Create a new model...
                TableModel model = ... // create a new table model

                // Apply the model to the table...
                applyModel(model);

            }
            try {
                Thread.sleep(100);
            } catch (InterruptedException ex) {
                Logger.getLogger(ThreadUpdates.class.getName()).log(Level.SEVERE, null, ex);
            }

        }

    }

    protected void applyModel(final TableModel model) {

        // Apply the model to the table, making sure you update within the
        // EDT
        try {
            EventQueue.invokeAndWait(new Runnable() {

                @Override
                public void run() {
                    table.setModel(model);
                }
            });
        } catch (InterruptedException | InvocationTargetException exp) {
            // Handle the update exception....
        }

    }

}

The problem with this is you're forcing the table to be fully update every time, this could become slow in time (as the quantity of data increases) and will invalidate the current selection.

If you can determine the last line you were up-to, you'd be better only adding those rows that have changed...

In that case the "apply" method could look like

protected void applyModel(final List<?> rowsToBeAdded) {

    // Apply the model to the table, making sure you update within the
    // EDT
    try {
        EventQueue.invokeAndWait(new Runnable() {
            @Override
            public void run() {

                MyUpdatableModel model = (MyUpdatableModel) table.getModel();
                model.addNewRows(rowsToBeAdded);

                // You will need to call fireTableRowsInserted(int firstRow, int lastRow)
                // indiciate where the new rows have been added, but this is best
                // done in the model

            }
        });
    } catch (InterruptedException interruptedException) {
    } catch (InvocationTargetException invocationTargetException) {
    }

}

This is a much nicer approach as it will only require the table to update those rows that have been updated and shouldn't effect the selection...

Answer 3

Besides what Dan wrote, to actually watch your file within the background thread, you could have a look at the WatchService API . This has been added to the SDK in Java 7 . It allows to register event listeners which are notified when a file has been changed.

Answer 4

This can be achieved by calling your TableModel 's fireTableDataChanged method. I am assuming that your table is backed by an implemention of an AbstractTableModel . If so, you just need to call fireTableDataChanged after reading the contents of your text file and updating the values in your table model. You can find some details here:

Java API

Edit: Following Dan's reply below - You would want your text file monitoring thread to trigger the fireTableDataChanged method.

Answer 5

I can't also auto-update. What I did was, I'm just closing the window add call the same window again.