Time for action – responding to the user

When the user clicks on the icon, nothing happens. That's because there is not a registered listener on TrayItem itself. There are two listeners that can be registered: a SelectionListener, called when the icon is clicked, and a MenuDetectListener which can respond to a context-sensitive menu. The former will be used to present a clock in its own window, which in SWT terms is called a Shell.

  1. Open the Activator class.
  2. Add a field to store a Shell:
    private Shell shell;
  3. Go to the run() method inside the Runnable in the Activator class's start() method.
  4. After the creation of the TrayItem, call addSelectionListener(), which creates a new Shell with a ClockView:
    trayItem.addSelectionListener(new SelectionListener() {
  public void widgetSelected(SelectionEvent e) {
    if (shell == null) {
      shell = new Shell(trayItem.getDisplay());
      shell.setLayout(new FillLayout());
      new ClockWidget(shell, SWT.NONE, new RGB(255, 0, 255));
      shell.pack();
    }
    shell.open();
  }
});
  5. Run the Eclipse instance, open the Clock View and click on the tray icon. A windowed clock will be shown:
    Time for action – responding to the user
  6. Ensure that the Shell is disposed when the bundle is stopped, so add the following to the end of the Activator class 's stop() method:
    if (shell != null && !shell.isDisposed()) {
  Display.getDefault().asyncExec(new Runnable() {
    public void run() {
      if (shell != null && !shell.isDisposed())
        shell.dispose();
    }
  });
}
  7. Run the Eclipse instance, click on the TrayItem, and use the host OSGi console to stop and start the bundle. The window should disappear when the bundle is stopped.

What just happened?

When TrayItem is installed into the system's Tray, event listeners can be registered to respond to user input. The one that gets called when the icon is clicked is the SelectionListener, and this gives the opportunity to display the window (or Shell in SWT's terminology).

The Display associated with the TrayItem is used when instantiating the Shell. Although either Display.getDefault() or Display.getCurrent() could be used, neither of these would be the right option. When developers are running in multi-monitor mode, or with a virtual display that spans multiple desktops, it's important to ensure that the Shell is shown on the same display as the corresponding Tray.

Without a LayoutManager, the clock won't show up. FillLayout is used here to ensure that the clock is made as large as the window (and resizes accordingly to the window itself). Once the window is created the pack() method is called, which sets the size of the window to the preferred size of its children; in this case, ClockView.

Finally, the window is shown with the open() call.

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