@Override
  public void bind() {
    // set handler of counter button
    display.setClickHandler(
        new ClickHandler() {

          @Override
          public void onClick(ClickEvent event) {
            counter++;
            display.setNofClicks("" + counter);
          }
        });

    // set handler of back button
    display.setBackHandler(
        new ClickHandler() {

          @Override
          public void onClick(ClickEvent event) {
            controller.start(null);
          }
        });
  }
 @Override
 public void present(HasWidgets container) {
   container.clear();
   container.add(display.asWidget());
 }