code: public void open() {
      state = State.OPENED;
      showIcons(true);
  
      animator[LEFT].setFloatValues(button[LEFT], 0);
      animator[RIGHT].setFloatValues(button[RIGHT], width);
      animator[RADIUS].setFloatValues(button[RADIUS], 0);
      animator[TOP].setFloatValues(button[TOP], 0);
      animator[BOTTOM].setFloatValues(button[BOTTOM], height);
  
      animatorSet.cancel();
      animatorSet.start();
      if (iconOpenedDrawable instanceof Animatable) {
        ((Animatable) iconOpenedDrawable).start();
      }
      ViewGroup parentView = (ViewGroup) TapBarMenu.this.getParent();
      this.animate()
          .y(menuAnchor == MENU_ANCHOR_BOTTOM ? parentView.getBottom() - height : 0)
              .setDuration(animationDuration)
              .setInterpolator(DECELERATE_INTERPOLATOR)
              .start();
    }
docs: Open the menu.