Recyclerview is so slow with a lot of item

I have made this code that could retrieve from realm 50k items and show it in recyclerview:

final RealmResults<AirportR> airps = realm.where(AirportR.class).findAll(); airrports = realm.copyFromRealm(airps, 0);

That's because you're copying 50000 objects from your zero-copy database on your UI thread.

Solutions:

1.) don't copy the elements out from the zero-copy database

2.) copy out 50000 elements into memory on a background thread and have fun with the memory usage

Honestly, it's quite obvious that #2 isn't a real solution, so instead, you should follow the practices of how to use Realm's lazy query evaluation feature and managed objects, rather than trying to hack it by calling realm.copyFromRealm()

So this is solution #1 :

public class ListAirportFragment
        extends Fragment {
    Realm realm;
    RealmResults<AirportR> airps;
    RecyclerView recyclerView;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_list_airport, container, false);

        RealmConfiguration defaultConfig = new RealmConfiguration.Builder().deleteRealmIfMigrationNeeded().build();
        realm = Realm.getInstance(defaultConfig);

        recyclerView = (RecyclerView) rootView.findViewById(R.id.recyclerview);
        SearchView searchView = (SearchView) rootView.findViewById(R.id.searchview);

        airps = realm.where(AirportR.class).findAll();

        recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
        final AirportAdapter adapter = new AirportAdapter(realm, airps, getActivity());
        recyclerView.setAdapter(adapter);

        searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
            @Override
            public boolean onQueryTextSubmit(String query) {
                return false;
            }

            @Override
            public boolean onQueryTextChange(String newText) {
                adapter.getFilter().filter(newText);
                return true;
            }
        });

        return rootView;
    }

    private class AirportAdapter
            extends RecyclerView.Adapter<RecyclerView.ViewHolder>
            implements Filterable {
        private RealmResults<AirPort> listAirports;
        private Context context;
        private Realm realm;

        private final RealmChangeListener realmChangeListener = new RealmChangeListener() {
            @Override
            public void onChange(Object element) {
                notifyDataSetChanged();
            }
        };

        public AirportAdapter(Realm realm, RealmResults<AirportR> airports, Context context) {
            this.realm = realm;
            this.listAirports = airports;
            this.listAirports.addChangeListener(realmChangeListener);
            this.context = context;
        }

        @Override
        public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.airport_show, parent, false);
            AirportClass holder = new AirportClass(view);
            return holder;
        }

        @Override
        public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
            AirportR airportR = listAirports.get(position);

            AirportClass mHolder = (AirportClass) holder;

            mHolder.country.setText(airportR.getIsoCountry());
            mHolder.name.setText(airportR.getName());
        }

        @Override
        public int getItemCount() {
            if(listAirports == null || !listAirports.isValid()) {
                return 0;
            }
            return listAirports.size();
        }

        @Override
        public Filter getFilter() {
            if(filter == null) {
                filter = new AirportFilter(this);
            }
            return filter;
        }

        private class AirportFilter
                extends Filter {
            private final AirportAdapter adapter;

            private AirportFilter(AirportAdapter adapter) {
                super();
                this.adapter = adapter;
            }

            @Override
            protected FilterResults performFiltering(CharSequence constraint) {
                final FilterResults results = new FilterResults();
                return results;
            }

            @Override
            protected void publishResults(CharSequence constraint, FilterResults results) {
                if(adapter.listAirports != null && adapter.listAirports.isValid()) {
                    adapter.listAirports.removeChangeListener(adapter.realmChangeListener);
                }
                if(constraint.length() == 0) {
                    adapter.listAirports = adapter.realm.where(AirportR.class).findAll();
                } else {
                    final String filterPattern = constraint.toString().toLowerCase().trim();
                    adapter.listAirports = adapter.realm.where(AirportR.class)
                                                .contains("fieldToQueryBy", filterPattern, Case.INSENSIIVE) // TODO: change field
                                                .findAll();
                }
                adapter.listAirports.addChangeListener(adapter.realmChangeListener);
                adapter.notifyDataSetChanged();
            }
        }

        private class AirportClass
                extends RecyclerView.ViewHolder {
            TextView name, country;
            ImageView image;

            public AirportClass(View itemView) {
                super(itemView);
                name = (TextView) itemView.findViewById(R.id.name);
                country = (TextView) itemView.findViewById(R.id.country);
                image = (ImageView) itemView.findViewById(R.id.imageView);
            }
        }
    }
}

This solution didn't use RealmRecyclerViewAdapter and managed adding/removing change listener manually, but you can also use RealmRecyclerViewAdapter for a better looking solution.