public CloseAction(Environment environment) {
		super("Dismiss Tab", null);
		this.environment = environment;
		putValue(ACCELERATOR_KEY, KeyStroke.getKeyStroke(KeyEvent.VK_ESCAPE,
				MAIN_MENU_MASK));
		environment.addChangeListener(new ChangeListener() {
			public void stateChanged(ChangeEvent e) {
				checkEnabled();
			}
		});
		checkEnabled();
	}