gistfile1.txt

bottomSheetBehavior.addBottomSheetCallback(new BottomSheetBehavior.BottomSheetCallback() {
            @Override
            public void onStateChanged(@NonNull View bottomSheet, int newState) {
                if (newState == BottomSheetBehavior.STATE_EXPANDED) {
                    // do stuff when the drawer is expanded
                }

                if (newState == BottomSheetBehavior.STATE_COLLAPSED) {
                    // do stuff when the drawer is collapsed
                }
            }

            @Override
            public void onSlide(@NonNull View bottomSheet, float slideOffset) {
                // do stuff during the actual drag event for example
                // animating a background color change based on the offset

                // or for example hidding or showing a fab
                if (slideOffset > 0.2) {
                    if (fab.isShown()) {
                        fab.hide();
                    }
                } else if (slideOffset < 0.15) {
                    if (!fab.isShown()) {
                        fab.show();
                    }
                }
            }
        });