List view with sticky headers and filtering

BrandListFragment.java

public class BrandListFragment extends BaseFragment {

    private static final String ARGS_LOCATION_SPEC = "location_spec";

    private LocationSpec location;

    @InjectView(R.id.progress)   View                      progress;
    @InjectView(R.id.brand_list) StickyListHeadersListView brandList;

    private Subscription dataSubscription;

    public static BaseFragment newInstance(LocationSpec spec) {
        Bundle args = new Bundle();
        args.putString(ARGS_LOCATION_SPEC, spec.serialize());

        BaseFragment f = new BrandListFragment();
        f.setArguments(args);

        return f;
    }

    @Override public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.brand_list, container, false);
        ButterKnife.inject(this, v);

        View header = inflater.inflate(R.layout.brand_list_search, null);
        brandList.addHeaderView(header);

        dataSubscription = dataService.onData((navTree, brands) -> {
            location = LocationSpec.deserialize(navTree, getArguments().getString(ARGS_LOCATION_SPEC));

            if (progress != null) {
                BrandAdapter adapter = new BrandAdapter(getActivity(), brands.getByGender(location.getGender()), location, navigator, api);

                EditText searchInput = findById(header, R.id.brand_search);
                searchInput.setHint(getString(R.string.brand_list_search_hint, brands.getByGender(location.getGender()).size()));
                searchInput.addTextChangedListener(new TextWatcher() {
                    @Override public void onTextChanged(CharSequence s, int start, int before, int count) {
                        adapter.getFilter().filter(s);
                    }

                    @Override public void afterTextChanged(Editable s) {}

                    @Override public void beforeTextChanged(CharSequence s, int start, int count, int after) {}
                });

                progress.setVisibility(View.GONE);
                brandList.setVisibility(View.VISIBLE);
                brandList.setAdapter(adapter);
            }
        });

        return v;
    }

    @Override public void onDestroyView() {
        hideKeyboard();
        super.onDestroyView();
        dataSubscription.unsubscribe();
    }

    private static class BrandAdapter extends BindableAdapter<NavigationItem> implements StickyListHeadersAdapter, Filterable {

        private LocationSpec         defaultLocation;
        private Navigator            navigator;
        private Bpi             api;
        private List<NavigationItem> brands;
        private List<NavigationItem> favorites;
        private List<NavigationItem> popular;
        private List<NavigationItem> filtered;

        private boolean isFilterOn;

        private OnClickListener itemClickListener = (view) -> {
            NavigationItem brand = (NavigationItem) view.getTag();
            LocationSpec location = new LocationSpec(defaultLocation);
            location.subNavItem(brand);
            navigator.goToProductListing(location);
        };

        private OnClickListener favoritesBtnClickListener = (view) -> {
            NavigationItem brand = (NavigationItem) view.getTag();

            Callback<NavigationItem> cb = new Callback<NavigationItem>() {
                @Override public void success(NavigationItem navigationItem, Response response) {}

                @Override public void failure(RetrofitError error) {}
            };

            if (brand.isFavorite()) {
                api.unfavoriteBrand(brand.getBrandId(), cb);
                favorites.remove(brand);
            } else {
                api.favoriteBrand(brand.getBrandId(), cb);
                favorites.add(brand);
            }

            brand.setFavorite(!brand.isFavorite());
            view.setActivated(brand.isFavorite());

            notifyDataSetChanged();
        };

        BrandAdapter(Context context, List<NavigationItem> brands, LocationSpec defaultLocation, Navigator navigator, Api api) {
            super(context);
            this.brands = brands;
            this.navigator = navigator;
            this.api = api;
            this.defaultLocation = defaultLocation;

            favorites = new ArrayList<>();
            popular = new ArrayList<>();
            for (NavigationItem b : brands) {
                if (b.isFavorite()) {
                    favorites.add(b);
                }
                if (b.isPopular()) {
                    popular.add(b);
                }
            }
        }

        @Override public int getCount() {
            return !isFilterOn
                ? brands.size() + popular.size() + favorites.size()
                : filtered.size();
        }

        @Override public NavigationItem getItem(int position) {
            if (isFilterOn) {
                return filtered.get(position);
            } else if (position < favorites.size()) {
                return favorites.get(position);
            } else if (position < favorites.size() + popular.size()) {
                return popular.get(position - favorites.size());
            } else {
                return brands.get(position - favorites.size() - popular.size());
            }
        }

        @Override public long getItemId(int position) {
            // A bit lame to make ids unique this way, but should do the job
            if (isFilterOn) {
                return getItem(position).getId();
            } else if (position < favorites.size()) {
                return getItem(position).getId() * 3;
            } else if (position < favorites.size() + popular.size()) {
                return getItem(position).getId() * 2;
            } else {
                return getItem(position).getId();
            }
        }

        @Override public View newView(LayoutInflater inflater, int position, ViewGroup container) {
            View v = inflater.inflate(R.layout.brand_list_item, container, false);
            BrandItemHolder holder = new BrandItemHolder();
            ButterKnife.inject(holder, v);
            v.setTag(holder);

            holder.title.setOnClickListener(itemClickListener);
            holder.favoriteBtn.setOnClickListener(favoritesBtnClickListener);

            return v;
        }

        @Override public void bindView(NavigationItem item, int position, View view) {
            BrandItemHolder holder = (BrandItemHolder) view.getTag();

            holder.brand = getItem(position);
            holder.title.setText(holder.brand.getTitle());
            holder.title.setTag(holder.brand);
            holder.favoriteBtn.setActivated(holder.brand.isFavorite());
            holder.favoriteBtn.setTag(holder.brand);
        }

        @Override public boolean areAllItemsEnabled() {
            return false;
        }

        @Override public View getHeaderView(int position, View view, ViewGroup viewGroup) {
            View v = (view != null)
                ? view
                : LayoutInflater.from(getContext()).inflate(R.layout.brand_list_header, viewGroup, false);

            TextView title = findById(v, R.id.header_title);

            // <...>

            title.getLayoutParams().height = !isFilterOn
                ? getContext().getResources().getDimensionPixelSize(R.dimen.margin_4x)
                : 0;

            title.setVisibility(
                isFilterOn ? View.GONE : View.VISIBLE
            );

            return v;
        }

        @Override public long getHeaderId(int position) {
            if (isFilterOn) {
                return 1;
            } else if (position < favorites.size()) {
                return 2;
            } else if (position < favorites.size() + popular.size()) {
                return 3;
            } else {
                return getItem(position).getTitle().charAt(0);
            }
        }

        @Override public Filter getFilter() {
            Filter filter = new Filter() {

                @Override protected void publishResults(CharSequence constraint, FilterResults results) {
                    if (constraint.length() == 0) {
                        isFilterOn = false;
                    } else {
                        isFilterOn = true;
                        filtered = (List<NavigationItem>) results.values;
                    }

                    notifyDataSetChanged();
                }

                @Override
                protected FilterResults performFiltering(CharSequence constraint) {

                    FilterResults results = new FilterResults();
                    ArrayList<NavigationItem> filteredBrands = new ArrayList<>();

                    if (constraint.length() > 0) {
                        constraint = constraint.toString().toLowerCase();
                        for (NavigationItem brand : brands) {
                            if (brand.getTitle().toLowerCase().startsWith(constraint.toString())) {
                                filteredBrands.add(brand);
                            }
                        }

                        results.count = filteredBrands.size();
                        results.values = filteredBrands;
                    }

                    return results;
                }
            };

            return filter;
        }
    }

    static class BrandItemHolder {

        NavigationItem brand;

        @InjectView(R.id.brand_title)           TextView title;
        @InjectView(R.id.brand_favorite_toggle) View     favoriteBtn;
    }
}