/* (non-Javadoc)
* @see com.google.gwt.user.client.ui.SourcesKeyboardEvents#addKeyboardListener(com.google.gwt.user.client.ui.KeyboardListener)
*/
public void addKeyboardListener(KeyboardListener listener) {
if (keyboardListeners == null)
keyboardListeners = new KeyboardListenerCollection();
keyboardListeners.add(listener);
}