Android: AutoCompleteTextView with Realm.io database

CountryAutoCompleteAdapter.java

/*
 * Copyright 2015 Yuriy Mysochenko
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
public class CountryAutoCompleteAdapter extends BaseAdapter implements Filterable {

    private Context mContext;
    private List<Country> mResult = new ArrayList<>();

    public CountryAutoCompleteAdapter(Context context) {
        mContext = context;
    }

    @Override
    public int getCount() {
        return mResult.size();
    }

    @Override
    public Country getItem(int index) {
        return mResult.get(index);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        if (convertView == null) {
            LayoutInflater inflater = (LayoutInflater) mContext
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = inflater.inflate(android.R.layout.simple_spinner_dropdown_item, parent, false);
        }
        ((TextView) convertView.findViewById(android.R.id.text1)).setText(getItem(position).getName());
        return convertView;
    }

    @Override
    public Filter getFilter() {
        return new Filter() {
            @Override
            protected FilterResults performFiltering(CharSequence constraint) {
                return null;
            }

            @Override
            protected void publishResults(CharSequence constraint, FilterResults results) {
                // filter data in UI thread instead of background one because of Realm limitation:
                // the data cannot be passed across threads
                if (constraint != null) {
                    String query = constraint.toString().toLowerCase();
                    mResult = filterCountries(query);
                    notifyDataSetChanged();
                } else {
                    notifyDataSetInvalidated();
                }
            }};
    }

    @NonNull
    private List<Country> filterCountries(String query) {
        Realm mRealm = Realm.getDefaultInstance();
        return mRealm
                .where(Country.class)
                .beginsWith("name", query, false)
                .findAll();
    }

}