Michael Nascimento Santos's Blog

February 2007 Archives

Displaying messages in the system tray

Many folks are aware that Java SE 6 comes with the new SystemTray and TrayIcon classes that allows an icon to be added to the system tray - or status area or whatever it is called on your platform. One very cool feature that most articles/pieces don't mention is it is possible to display a message similar to the "Low battery" warning produced by laptops or the "Updates are ready to be installed" alert Windows Update displays so often.

Here is the code:

public class SysTray {
   public static void main(String[] args) throws Exception {
      TrayIcon icon = new TrayIcon(getImage(), "Java application as a tray icon", 
            createPopupMenu());
      icon.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent e) {
            JOptionPane.showMessageDialog(null, "Hey, you activated me!");
         }
      });
      SystemTray.getSystemTray().add(icon);

      Thread.sleep(3000);

      icon.displayMessage("Attention", "Please click here", 
            TrayIcon.MessageType.WARNING);
   }

   private static Image getImage() throws HeadlessException {
      Icon defaultIcon = MetalIconFactory.getTreeHardDriveIcon();
      Image img = new BufferedImage(defaultIcon.getIconWidth(), 
            defaultIcon.getIconHeight(), BufferedImage.TYPE_4BYTE_ABGR);
      defaultIcon.paintIcon(new Panel(), img.getGraphics(), 0, 0);

      return img;
   }

   private static PopupMenu createPopupMenu() throws HeadlessException {
      PopupMenu menu = new PopupMenu();

      MenuItem exit = new MenuItem("Exit");
      exit.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent e) {
            System.exit(0);
         }
      });
      menu.add(exit);

      return menu;
   }
}

When you run this sample, an hard-drive icon (borrowed from Swing's Metal L&F) will be displayed in the system tray. If you place the mouse over it for a few seconds, the "Java application as a tray icon" tooltip will be shown and right-clicking it will show a popup menu with a single option, Exit, that will terminate our sample.

The cool thing is that approximately 3 seconds after the icon appears, a warning message will pop up in your system tray - and if you are running Windows and hide the task bar, it will even become immediately visible. This feature can be quite useful for some scenario, such as monitoring applications.

There are several other hidden gems in Java SE 6. Let's keep on searching for them...

It's high time: a Date and Time API for the Java SE Platform

A few times in the past I've considered writing a blog entry summing up all the problems with Date, Calendar, TimeZone, DST rules and other JDK related classes. If you think these APIs are simple, functional and do not cause any harm, believe me, you really haven't done anything trivial with dates. Besides the classic "days are 1-based, month are 0-based" issues and the lack of many major concepts, such as date without time, any date/time calculation fails miserably when it includes a DST start or end date. There are simply too many issues with the current API to list here.

However, the point of this entry is not to bash the current Java SE API, but rather to talk about JSR-310: Date and Time API. As stated in the JSR, it "will provide a new and improved date and time API for Java. The main goal is to build upon the lessons learned from the first two APIs (Date and Calendar) in Java SE, providing a more advanced and comprehensive model for date and time manipulation."

Our main inspiration will be Joda-Time, a great open-source library originally created by Stephen Colebourne (who will be co-leading the JSR), that you should definitely use today to deal with date and time. We won't simply rename Joda-Time and bless it with the JCP approval stamp. We actually want to learn from it, use Java SE 5 features to design an easier-to-use API, remove all deprecated, complex and not mature enough features and also consider addressing a few issues currently not solved by it.

If you want to help us, join the jsr-310 java.net project and subscribe to the mailing lists. If you think you are an expert on the matter, consider joining the expert group. We intend to run this JSR as transparently as possible though, so your voice will be heard even if you just join the java.net project.

This work is licensed under a Creative Commons License.