Java™ Platform
Standard Ed. 6

java.awt
Class SystemTray

java.lang.Object
  extended by java.awt.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 Summary
 void add(TrayIcon trayIcon)
          Adds a TrayIcon to the SystemTray.
 void addPropertyChangeListener(String propertyName, PropertyChangeListener listener)
          Adds a PropertyChangeListener to the listener list for a specific property.
 PropertyChangeListener[] getPropertyChangeListeners(String propertyName)
          Returns an array of all the listeners that have been associated with the named property.
static SystemTray getSystemTray()
          Gets the SystemTray instance that represents the desktop's tray area.
 TrayIcon[] getTrayIcons()
          Returns an array of all icons added to the tray by this application.
 Dimension getTrayIconSize()
          Returns the size, in pixels, of the space that a tray icon will occupy in the system tray.
static boolean isSupported()
          Returns whether the system tray is supported on the current platform.
 void remove(TrayIcon trayIcon)
          Removes the specified TrayIcon from the SystemTray.
 void removePropertyChangeListener(String propertyName, PropertyChangeListener listener)
          Removes a PropertyChangeListener from the listener list for a specific property.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Method Detail

getSystemTray

public static SystemTray getSystemTray()
Gets the SystemTray instance that represents the desktop's tray area. This always returns the same instance per application. On some platforms the system tray may not be supported. You may use the isSupported() method to check if the system tray is supported.

If a SecurityManager is installed, the AWTPermission accessSystemTray must be granted in order to get the SystemTray instance. Otherwise this method will throw a SecurityException.

Returns:
the SystemTray instance that represents the desktop's tray area
Throws:
UnsupportedOperationException - if the system tray isn't supported by the current platform
HeadlessException - if GraphicsEnvironment.isHeadless() returns true
SecurityException - if accessSystemTray permission is not granted
See Also:
add(TrayIcon), TrayIcon, isSupported(), SecurityManager.checkPermission(java.security.Permission), AWTPermission

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 listener list for a specific property. Currently supported property:

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)

removePropertyChangeListener

public void removePropertyChangeListener(String propertyName,
                                         PropertyChangeListener listener)
Removes a PropertyChangeListener from the listener list for a specific property.

The PropertyChangeListener must be from this context.

If propertyName or listener is null or invalid, no exception is thrown and no action is taken.

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

getPropertyChangeListeners

public PropertyChangeListener[] getPropertyChangeListeners(String propertyName)
Returns an array of all the listeners that have been associated with the named property.

Only the listeners in this context are returned.

Parameters:
propertyName - the specified property
Returns:
all of the PropertyChangeListeners associated with the named property; if no such listeners have been added or if propertyName is null or invalid, an empty array is returned
See Also:
addPropertyChangeListener(java.lang.String, java.beans.PropertyChangeListener), removePropertyChangeListener(java.lang.String, java.beans.PropertyChangeListener)

Java™ Platform
Standard Ed. 6

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