I have been pulling my hair out over a JTextField I am using as a status bar which just doesn't seem to respond when I set the text. Here is the method the constructor calls to make the status bar:

private void makeStatusBar() {
statusField = new JTextField();
statusField.setEditable(false);
statusField.setForeground(Color.black);
statusField.setFont(new Font("TimesRoman", Font.PLAIN, 12));
}

And here is part of my actionPerformed method which makes use of the status bar:

statusField.setText(" Connecting with database ...");
Data[] temp = database.search(queryFieldText);
statusField.setText("");

The database.search method is an invocation of a remote method, and while testing I have deliberately put a two second delay in the search() method to simulate a network delay. But my status panel remains stubbornly blank.

Does a separate thread look after the text setting and is it possible that before it gets a look in the next line is being executed?

I've checked out this forum and have seen advice on SwingUtilities.invokeAndWait(), but this seems very complicated and so far my experiments have ended in failure!

Any ideas?
Thanks, Rob

 

 

The problem, as I understand how swing works, is that repainting of components is only done when the event thread is free. Therefore, Swing doesn't get a chance to paint the status bar before the text is reset to "". Here is a solution that uses the paintImmediately() method.

import java.awt.;
import java.awt.event.;
import javax.swing.;
import javax.swing.border.;
import javax.swing.text.*;

public class StatusBar extends JFrame
{
JTextField statusBar;

public StatusBar()
{
JPanel panel = new JPanel();
panel.setLayout( new BorderLayout() );
setContentPane( panel );

JButton button = new JButton( "Connect..." );
panel.add( button, BorderLayout.NORTH );

button.addActionListener( new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
statusBar.setText( "Connecting to database..." );
Dimension dim = statusBar.getSize();
statusBar.paintImmediately(0, 0, dim.width, dim.height);

try
{
Thread.sleep( 2000 );
}
catch (Exception exc) {}

statusBar.setText( "" );
}
});

statusBar = new JTextField();
panel.add( statusBar, BorderLayout.SOUTH );
}

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

 

 

Thanks for bringing to my attention the JComponent paintImmediately method - it worked!

 

 

Thanks very much for this tip as I was having similar problems with a recursive routine that needed to show an update with each iteration.

A great help.

 

 

paintImmediately() is just a dirty hack, e.g. it won't help you with layout-updates or repaints when your component was obscured.

If you want a real solution, you have to get used to SwingWorker. Or take a look at http://spin.sourceforge.net .

Sven

 

 

Sven,

Could you provide a simple example based around SwingWorker for the problem mentioned? Spin looks good but a bit overwhelming at the moment.

Many thanks
Benoit

 

 

public void actionPerformed(ActionEvent ev) {
 
  statusField.setText(" Connecting with database ...");
 
  final queryFieldText = queryField.getText();
 
  new SwingWorker() {
    public Object construct() {
      return database.search(queryFieldText);
    }
 
    public void finished() {
      Data[] temp = (Data[])getValue();
 
      // show data on the GUI
 
      statusField.setText("");
    }
  }).start();
}

 

 

just a thought. i think that you should try using a JLabel, instead of an uneditable JTextField. you might find that it looks better. it's probably better form anyway.