SystemTray (Java Platform SE 8 )
Keywords: java.awt.SystemTray class
Date: 2015-11-18

java.awt

## Class SystemTray

- java.lang.Object
- - 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

    All Methods Static Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `add(TrayIcon trayIcon)` Adds a `TrayIcon` to the `SystemTray`.
    `void` | `addPropertyChangeListener(String propertyName, PropertyChangeListener listener)` Adds a `PropertyChangeListener` to the list of listeners for the 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 list of listeners for the specific property. The following properties are currently supported:

      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)`

    - #### 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 `PropertyChangeListener`s 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)`

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