Time panel shows the current time. : JLabel « Swing « Java Tutorial

 * Copyright (C) 2002-2003 Colin Bell
 * colbell@users.sourceforge.net
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * Lesser General Public License for more details.
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
import java.awt.Dimension;
import java.awt.FontMetrics;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.DateFormat;
import java.util.Calendar;

import javax.swing.JLabel;
import javax.swing.Timer;
import javax.swing.border.Border;
 * Time panel. This will show the current time.
 * A timer to update the time is started when the component
 * is added to its parent and stopped when removed from its parent.
 * @author <A HREF="mailto:colbell@users.sourceforge.net">Colin Bell</A>
public class TimePanel extends JLabel implements ActionListener
  /** Timer that updates time. */
  private Timer _timer;

  /** Used to format the displayed date. */
  private DateFormat _fmt = DateFormat.getTimeInstance(DateFormat.LONG);
  private Dimension _prefSize;
  private Calendar _calendar = Calendar.getInstance();

   * Default ctor.
  public TimePanel()
    super("", JLabel.CENTER);

   * Add component to its parent. Start the timer for auto-update.
  public void addNotify()
    _timer = new Timer(1000, this);

   * Remove component from its parent. Stop the timer.
  public void removeNotify()
    if (_timer != null)
      _timer = null;

   * Update component with the current time.
   * @param evt   The current event.
  public void actionPerformed(ActionEvent evt)

   * Return the preferred size of this component.
   * @return  the preferred size of this component.
  public Dimension getPreferredSize()
    if(null == _prefSize)
      // This was originaly done every time.
      // and the count of instantiated objects was amazing
      _prefSize = new Dimension();
      _prefSize.height = 20;
      FontMetrics fm = getFontMetrics(getFont());
      Calendar cal = Calendar.getInstance();
      cal.set(Calendar.HOUR_OF_DAY, 23);
      cal.set(Calendar.MINUTE, 59);
      cal.set(Calendar.SECOND, 59);
      _prefSize.width = fm.stringWidth(_fmt.format(cal.getTime()));
      Border border = getBorder();
      if (border != null)
        Insets ins = border.getBorderInsets(this);
        if (ins != null)
          _prefSize.width += (ins.left + ins.right);
      Insets ins = getInsets();
      if (ins != null)
        _prefSize.width += (ins.left + ins.right) + 20;
    return _prefSize;

14.3.2.Create JLabel component
14.3.3.Create a JLabel with an image icon
14.3.4.JLabel is for displaying text, images or both. It does not react to input events.
14.3.5.Horizontal Alignment: CENTER
14.3.6.Vertical Alignment: CENTER
14.3.7.Horizontal Alignment: LEFT
14.3.8.Vertical Alignment: TOP
14.3.9.Horizontal Alignment: RIGHT
14.3.10.Vertical Alignment: BOTTOM
14.3.11.The text is horizontally and vertically centered
14.3.12.The text is right-justified and vertically centered
14.3.13.The text is left-justified and top-aligned
14.3.14.The text is right-justified and top-aligned
14.3.15.The text is left-justified and bottom-aligned
14.3.16.The text is right-justified and bottom-aligned
14.3.17.Add Icon to JLabelAdd Icon to JLabel
14.3.18.Mix Icon and text in JLabelMix Icon and text in JLabel
14.3.19.Set Font and foreground color for a JLabelSet Font and foreground color for a JLabel
14.3.20.Load image from disk file and add it to a JLabelLoad image from disk file and add it to a JLabel
14.3.21.Using JLabel Mnemonics: Interconnect a specific JLabel and JTextField.Using JLabel Mnemonics: Interconnect a specific JLabel and JTextField.
14.3.22.Using a JLabel and pass in HTML for the textUsing a JLabel and pass in HTML for the text
14.3.23.Multiline label (HTML)
14.3.24.JLabel with more than one row
14.3.25.A simple Bean which extends JLabel
14.3.26.Add JLabel to JScrollPane
14.3.27.Disable a label
14.3.28.Unicode with Label
14.3.29.Customizing a JLabel Look and Feel
14.3.30.Associate JLabel component with a JTextField
14.3.31.Setting the Focus of a JTextField Component Using a JLabel Component
14.3.32.JLabel with lined border
14.3.33.A Label that uses inline HTML to format its text
14.3.34.A label with no indication it has been clicked
14.3.35.Adding Drag-and-Drop Support to a JLabel Component
14.3.36.Have a Label with underlined text
14.3.37.Multi Line Label
14.3.38.Vertical Label UI
14.3.39.Time panel shows the current time.
14.3.40.URL Label
14.3.41.Hyperlink Label
14.3.42.Gradient Label