ZooFragment.java

...

        ZooFragmentViewModel viewModel = ViewModelProviders.of(this).get(ZooFragmentViewModel.class);
        viewModel.getZooUpdateResponse().observe(this, response -> {
            if (response != null) {
                switch (response.getStatus()) {
                    case Response.STATUS_LOADING:
                        showProgressBar(true);
                        break;
                    case Response.STATUS_SUCCESS:
                        dismiss();
                        break;
                    case Response.STATUS_FAIL:
                        showProgressBar(false);
                        Toast.makeText(getContext(), response.getErrorMessage(), Toast.LENGTH_SHORT).show();
                        break;
                }
            }
        });

...