JLabel updating text

Question

Hi,
I have a panel called BottomPanel that is used in three frames.
The same instance of BottomPanel is always used.
I want the BottomPanel to do the following, every 10 seconds to change the text of a JLabel to "current time is XX".
The issue I have is that when the JLabels.setText is invoked within the panel with the new text is not be shown in the panel.
I have tried calling revaliate and repaint and no luck.
I want the panel to handle this itself as it will be called from a number of frames.
A BottomPanelManager is called by the frames to get the BottomPanel (always the same instance).
Any help would be much appreciated
Cheers

Answer 1

You need to emulate Swing by creating a non-GUI model object to underlie the logic of this JPanel. Then create 3 new JPanels and have them all share the same model.
edit: for instance:
BottomPanelModel.java
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import javax.swing.Timer;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
public class BottomPanelModel
  private static final int DELAY = 1000;
  private SimpleDateFormat sdFormat = new SimpleDateFormat("hh:mm:ss a");
  private int delay = DELAY;
  private Timer swingTimer = new Timer(delay, new TimerListener());
  private List<ChangeListener> changeListenerList = new ArrayList<ChangeListener>();
  public BottomPanelModel(int delay)
    this.delay = delay;
    swingTimer.setDelay(delay);
    swingTimer.start();
  public BottomPanelModel()
    this(DELAY);
  public void addChangeListener(ChangeListener cl)
    changeListenerList.add(cl);
  public String getTimeString()
    Date date = new Date(System.currentTimeMillis());
    return sdFormat.format(date);
  private class TimerListener implements ActionListener
    public void actionPerformed(ActionEvent arg0)
      ChangeEvent changeEvent = new ChangeEvent(BottomPanelModel.this);
      for (ChangeListener listener : changeListenerList)
        listener.stateChanged(changeEvent);
}BottomPanel.java
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
public class BottomPanel extends JPanel
  private BottomPanelModel model;
  private JLabel timeLabel = new JLabel();
  public BottomPanel(BottomPanelModel model)
    this.model = model;
    add(timeLabel);
    model.addChangeListener(new ChangeListener()
      public void stateChanged(ChangeEvent arg0)
        timeLabel.setText(BottomPanel.this.model.getTimeString());
}BottomPanelTest.java
import java.awt.Dimension;
import java.awt.GridLayout;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class BottomPanelTest
  private static final Dimension MAIN_SIZE = new Dimension(400, 600);
  private static final int BOTTOM_COUNT = 8;
  private JPanel mainPanel = new JPanel();
  public BottomPanelTest()
    mainPanel.setLayout(new GridLayout(0, 1));
    mainPanel.setPreferredSize(MAIN_SIZE);
    BottomPanelModel bpModel = new BottomPanelModel();
    for (int i = 0; i < BOTTOM_COUNT; i++)
      BottomPanel bPanel = new BottomPanel(bpModel);
      mainPanel.add(bPanel);
  public JComponent getPanel()
    return mainPanel;
  private static void createAndShowGUI()
    JFrame frame = new JFrame("BottomPanelTest Application");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.getContentPane().add(new BottomPanelTest().getPanel());
    frame.pack();
    frame.setLocationRelativeTo(null);
    frame.setVisible(true);
  public static void main(String[] args)
    javax.swing.SwingUtilities.invokeLater(new Runnable()
      public void run()
        createAndShowGUI();
}Edited by: Encephalopathic on Jan 12, 2009 3:24 PM