Module java.desktop
Package java.awt

Class SystemTray


  • public class SystemTray
extends Object
    The SystemTray class represents the system tray for a desktop. On Microsoft Windows it is referred to as the "Taskbar Status Area", on Gnome it is referred to as the "Notification Area", on KDE it is referred to as the "System Tray". The system tray is shared by all applications running on the desktop.

    On some platforms the system tray may not be present or may not be supported, in this case getSystemTray() throws UnsupportedOperationException. To detect whether the system tray is supported, use isSupported().

    The SystemTray may contain one or more TrayIcons, which are added to the tray using the add(java.awt.TrayIcon) method, and removed when no longer needed, using the remove(java.awt.TrayIcon). TrayIcon consists of an image, a popup menu and a set of associated listeners. Please see the TrayIcon class for details.

    Every Java application has a single SystemTray instance that allows the app to interface with the system tray of the desktop while the app is running. The SystemTray instance can be obtained from the getSystemTray() method. An application may not create its own instance of SystemTray.

    The following code snippet demonstrates how to access and customize the system tray: 

     
     TrayIcon trayIcon = null;
     if (SystemTray.isSupported()) {
         // get the SystemTray instance
         SystemTray tray = SystemTray.getSystemTray();
         // load an image
         Image image = Toolkit.getDefaultToolkit().getImage(...);
         // create a action listener to listen for default action executed on the tray icon
         ActionListener listener = new ActionListener() {
             public void actionPerformed(ActionEvent e) {
                 // execute default action of the application
                 // ...
             }
         };
         // create a popup menu
         PopupMenu popup = new PopupMenu();
         // create menu item for the default action
         MenuItem defaultItem = new MenuItem(...);
         defaultItem.addActionListener(listener);
         popup.add(defaultItem);
         /// ... add other items
         // construct a TrayIcon
         trayIcon = new TrayIcon(image, "Tray Demo", popup);
         // set the TrayIcon properties
         trayIcon.addActionListener(listener);
         // ...
         // add the tray image
         try {
             tray.add(trayIcon);
         } catch (AWTException e) {
             System.err.println(e);
         }
         // ...
     } else {
         // disable tray option in your application or
         // perform other actions
         ...
     }
     // ...
     // some time later
     // the application state has changed - update the image
     if (trayIcon != null) {
         trayIcon.setImage(updatedImage);
     }
     // ...
    Since:
    1.6
    See Also:
    TrayIcon

    • Method Detail

      • isSupported

        public static boolean isSupported​()
        Returns whether the system tray is supported on the current platform. In addition to displaying the tray icon, minimal system tray support includes either a popup menu (see TrayIcon.setPopupMenu(PopupMenu)) or an action event (see TrayIcon.addActionListener(ActionListener)).

        Developers should not assume that all of the system tray functionality is supported. To guarantee that the tray icon's default action is always accessible, add the default action to both the action listener and the popup menu. See the example for an example of how to do this.

        Note: When implementing SystemTray and TrayIcon it is strongly recommended that you assign different gestures to the popup menu and an action event. Overloading a gesture for both purposes is confusing and may prevent the user from accessing one or the other.

        Returns:
        false if no system tray access is supported; this method returns true if the minimal system tray access is supported but does not guarantee that all system tray functionality is supported for the current platform
        See Also:
        getSystemTray()

      • add

        public void add​(TrayIcon trayIcon)
         throws AWTException
        Adds a TrayIcon to the SystemTray. The tray icon becomes visible in the system tray once it is added. The order in which icons are displayed in a tray is not specified - it is platform and implementation-dependent.

        All icons added by the application are automatically removed from the SystemTray upon application exit and also when the desktop system tray becomes unavailable.

        Parameters:
        trayIcon - the TrayIcon to be added
        Throws:
        NullPointerException - if trayIcon is null
        IllegalArgumentException - if the same instance of a TrayIcon is added more than once
        AWTException - if the desktop system tray is missing
        See Also:
        remove(TrayIcon), getSystemTray(), TrayIcon, Image

      • remove

        public void remove​(TrayIcon trayIcon)
        Removes the specified TrayIcon from the SystemTray.

        All icons added by the application are automatically removed from the SystemTray upon application exit and also when the desktop system tray becomes unavailable.

        If trayIcon is null or was not added to the system tray, no exception is thrown and no action is performed.

        Parameters:
        trayIcon - the TrayIcon to be removed
        See Also:
        add(TrayIcon), TrayIcon

      • getTrayIcons

        public TrayIcon[] getTrayIcons​()
        Returns an array of all icons added to the tray by this application. You can't access the icons added by another application. Some browsers partition applets in different code bases into separate contexts, and establish walls between these contexts. In such a scenario, only the tray icons added from this context will be returned.

        The returned array is a copy of the actual array and may be modified in any way without affecting the system tray. To remove a TrayIcon from the SystemTray, use the remove(TrayIcon) method.

        Returns:
        an array of all tray icons added to this tray, or an empty array if none has been added
        See Also:
        add(TrayIcon), TrayIcon

      • getTrayIconSize

        public Dimension getTrayIconSize​()
        Returns the size, in pixels, of the space that a tray icon will occupy in the system tray. Developers may use this methods to acquire the preferred size for the image property of a tray icon before it is created. For convenience, there is a similar method TrayIcon.getSize() in the TrayIcon class.
        Returns:
        the default size of a tray icon, in pixels
        See Also:
        TrayIcon.setImageAutoSize(boolean), Image, TrayIcon.getSize()

      • addPropertyChangeListener

        public void addPropertyChangeListener​(String propertyName,
                                      PropertyChangeListener listener)
        Adds a PropertyChangeListener to the list of listeners for the specific property. The following properties are currently supported:
        SystemTray properties
        Property Description
        trayIcons The SystemTray's array of TrayIcon objects. The array is accessed via the getTrayIcons() method.
        This property is changed when a tray icon is added to (or removed from) the system tray.
        For example, this property is changed when the system tray becomes unavailable on the desktop
        and the tray icons are automatically removed.
        systemTray This property contains SystemTray instance when the system tray is available or null otherwise.
        This property is changed when the system tray becomes available or unavailable on the desktop.
        The property is accessed by the getSystemTray() method.

        The listener listens to property changes only in this context.

        If listener is null, no exception is thrown and no action is performed.

        Parameters:
        propertyName - the specified property
        listener - the property change listener to be added
        See Also:
        removePropertyChangeListener(java.lang.String, java.beans.PropertyChangeListener), getPropertyChangeListeners(java.lang.String)