public DynamicToggleButton() {
        super("de.hpi3d.tracing.ui.dynamicToggleButton");
        comServ = (ICommandService) PlatformUI.getWorkbench()
        .getService(ICommandService.class);
        contextServ = (IContextService) PlatformUI
        .getWorkbench().getService(IContextService.class);
        ContextHelper.addListener(new ITracingContextListener() {

            public void handleEvent(TracingContextEvent event) {
                Type type = event.getType();
                if (type.equals(Type.TOGGLETRACING) || type.equals(Type.DEBUGGINGSESSION)) {
                    update();
                }
            }
        });
    }

    public void fill(ToolBar bar, int index) {
        item = new ToolItem(bar, SWT.PUSH);
        com = comServ.getCommand(TOGGLETRACINGCOMMANDID);
        update();

        item.addListener(SWT.Selection, new Listener() {
            public void handleEvent(Event event) {
                new ToggleTracingCommandUtils().toggleToggleTracingCommand();
                update();
            }
        });

    }