@Entity(tableName = "ruseng") //Описывает таблицу в БД
public class RusOther {
    @PrimaryKey(autoGenerate = true) //Система сама будет инкрементировать это поле в БД
    @ColumnInfo(typeAffinity = INTEGER)
    private int id;
    @ColumnInfo(typeAffinity = TEXT)
    private String word;
    @ColumnInfo(typeAffinity = TEXT)
    private String translation;
    @ColumnInfo(typeAffinity = INTEGER)
    private int favorites;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getWord() {
        return word;
    }

    public void setWord(String word) {
        this.word = word;
    }

    public String getTranslation() {
        return translation;
    }

    public void setTranslation(String translation) {
        this.translation = translation;
    }

    public int getFavorites() {
        return favorites;
    }

    public void setFavorites(int favorites) {
        this.favorites = favorites;
    }

    public RusOther(int id, String word, String translation, int favorites) {
        this.id = id;
        this.word = word;
        this.translation = translation;
        this.favorites = favorites;
    }
}

@Entity(tableName = "engrus") //Описывает таблицу в БД
public class OtherRus {
    @PrimaryKey(autoGenerate = true) //Система сама будет инкрементировать это поле в БД
    @ColumnInfo(typeAffinity = INTEGER)
    private int id;
    @ColumnInfo(typeAffinity = TEXT)
    private String word;
    @ColumnInfo(typeAffinity = TEXT)
    private String translation;
    @ColumnInfo(typeAffinity = INTEGER)
    private int favorites;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getWord() {
        return word;
    }

    public void setWord(String word) {
        this.word = word;
    }

    public String getTranslation() {
        return translation;
    }

    public void setTranslation(String translation) {
        this.translation = translation;
    }

    public int getFavorites() {
        return favorites;
    }

    public void setFavorites(int favorites) {
        this.favorites = favorites;
    }

    public OtherRus(int id, String word, String translation, int favorites) {
        this.id = id;
        this.word = word;
        this.translation = translation;
        this.favorites = favorites;
    }
}

@Dao
public interface RusOtherDao {

    @Query("SELECT * FROM ruseng")
    LiveData<List<RusOther>> getAllRusOtherWords(); //Через LiveData мы наблюдаем за списком и обновляем его при изменениях

    @Query("SELECT * FROM ruseng WHERE id = :id")
    RusOther getRusOtherByID(long id);
}

@Dao
public interface OtherRusDao {

    @Query("SELECT * FROM engrus")
    LiveData<List<OtherRus>> getAllOtherRusWords(); //Через LiveData мы наблюдаем за списком и обновляем его при изменениях

    @Query("SELECT * FROM engrusWHERE id = :id")
    OtherRus getOtherRusByID(long id);
}

public class AppViewModel extends AndroidViewModel {

    private AppDatabase appDataBase;

    public AppViewModel(Application application) {
        super(application);
        appDataBase = AppDatabase.createPersistentDatabase(this.getApplication());
    }

    //Получение всех слов с русского на другой язык
    public LiveData<List<RusOther>> getAllRusOtherWords(){
        return appDataBase.rusOtherDao().getAllRusOtherWords();
    }

    //Получение всех слов с другого на русский язык
    public LiveData<List<OtherRus>> getAllOtherRusWords(){
        return appDataBase.otherRusDao().getAllOtherRusWords();
    }

    public RusOther getByRusOtherId(long id){
        return appDataBase.rusOtherDao().getRusOtherByID(id);
    }
}

public class OtherRusAdapter extends RecyclerView.Adapter<OtherRusAdapter.WordViewHolder> implements Filterable {

    private List<OtherRus> mWords;
    private List<OtherRus> mFilteredList;
    private Context mContext;

    RusOtherAdapter.OnItemClickListener mItemClickListener;

    public interface OnItemClickListener {
        void onItemClick(long id);
    }

    public void setOnItemClickListener(final RusOtherAdapter.OnItemClickListener mItemClickListener) {
        this.mItemClickListener = mItemClickListener;
    }

    class WordViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {

        private final TextView txtWord;

        private WordViewHolder(final View itemView) {
            super(itemView);
            txtWord = itemView.findViewById(R.id.txtWord);
            itemView.setOnClickListener(this);
        }

        @Override
        public void onClick(View view) {
            switch (view.getId()) {
                default:
                    mItemClickListener.onItemClick(mFilteredList.get(getAdapterPosition()).getId());
            }
        }
    }

    public OtherRusAdapter(Context context, List<OtherRus> mWords) {
        this.mWords = mWords;
        this.mFilteredList = mWords;
        this.mContext = context;
    }

    @Override
    public WordViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View v = LayoutInflater.from(mContext).inflate(R.layout.item,parent,false);
        WordViewHolder vh = new WordViewHolder(v);
        return vh;
    }

    @Override
    public void onBindViewHolder(WordViewHolder holder, int position) {
        final OtherRus word = mFilteredList.get(position);
        holder.txtWord.setText(word.getWord());
    }

    @Override
    public int getItemCount() {
        return mFilteredList.size();
    }

    @Override
    public Filter getFilter() {
        return new Filter() {
            @Override
            protected FilterResults performFiltering(CharSequence charSequence) {

                String charString = charSequence.toString();

                if (charString.isEmpty()) {

                    mFilteredList = mWords;
                } else {

                    List<OtherRus> filteredList = new ArrayList<>();

                    for (OtherRus word : mWords) {

                        if (word.getWord().toLowerCase().contains(charString)) {

                            filteredList.add(word);
                        }
                    }

                    mFilteredList = filteredList;
                }

                FilterResults filterResults = new FilterResults();
                filterResults.values = mFilteredList;
                return filterResults;
            }

            @Override
            protected void publishResults(CharSequence charSequence, FilterResults filterResults) {
                mFilteredList = (List<OtherRus>) filterResults.values;
                notifyDataSetChanged();
            }
        };
    }
}

public class MainActivity extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener, RusOtherAdapter.OnItemClickListener, OtherRusAdapter.OnItemClickListener {

    private AppViewModel viewModel;

    private RecyclerView rvList;
    RusOtherAdapter rusOtherAdapter;
    OtherRusAdapter otherRusAdapter;

    private TextView txtLeftLang;
    private TextView txtRightLang;
    private ImageButton btnChangeLang;
    private boolean isOtherRight; //При запуске приложения False

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = findViewById(R.id.toolbar);
        ***
        txtLeftLang = findViewById(R.id.txtLeftLang);
        txtRightLang = findViewById(R.id.txtRightLang);
        btnChangeLang = findViewById(R.id.btnChangeLang);

        txtLeftLang.setText(getResources().getString(R.string.rus_lang));
        txtRightLang.setText(getResources().getString(R.string.other_lang));

        rvList = findViewById(R.id.rvList);
        rvList.setLayoutManager(new LinearLayoutManager(this));

        viewModel = ViewModelProviders.of(this).get(AppViewModel.class);

        viewModel.getAllRusOtherWords().observe(MainActivity.this, new Observer<List<RusOther>>() {
            @Override
            public void onChanged(@Nullable final List<RusOther> words) {
                for (int i = 0; i < words.size(); i++) {
                    System.out.println(words.get(i).getWord());
                }
                rusOtherAdapter = new RusOtherAdapter(MainActivity.this, words);
                rusOtherAdapter.setOnItemClickListener(MainActivity.this);
                rvList.setAdapter(rusOtherAdapter);
            }
        });

        btnChangeLang.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                txtRightLang.setText(isOtherRight? getResources().getString(R.string.other_lang):getResources().getString(R.string.rus_lang));
                txtLeftLang.setText(isOtherRight? getResources().getString(R.string.rus_lang):getResources().getString(R.string.other_lang));

                if (isOtherRight) { //перевод с русского на другой
                    rvList.setAdapter(null);
                    viewModel.getAllRusOtherWords().observe(MainActivity.this, new Observer<List<RusOther>>() {
                        @Override
                        public void onChanged(@Nullable final List<RusOther> words) {
                            rusOtherAdapter = new RusOtherAdapter(MainActivity.this, words);
                            rusOtherAdapter.setOnItemClickListener(MainActivity.this);
                            rvList.setAdapter(rusOtherAdapter);
                        }
                    });
                } else { // перевод с другого на русский
                    rvList.setAdapter(null);
                    viewModel.getAllOtherRusWords().observe(MainActivity.this, new Observer<List<OtherRus>>() {
                        @Override
                        public void onChanged(@Nullable final List<OtherRus> words) {
                            otherRusAdapter = new OtherRusAdapter(MainActivity.this, words);
                            otherRusAdapter.setOnItemClickListener(MainActivity.this);
                            rvList.setAdapter(otherRusAdapter);
                        }
                    });
                }

                isOtherRight = !isOtherRight;
            }
        });

    }

    @Override //Нажатие на элемент списка
    public void onItemClick(long id) {
        Toast.makeText(this, id + "", Toast.LENGTH_LONG).show();
    }

    public void search(SearchView searchView) {

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

                return false;
            }

            @Override
            public boolean onQueryTextChange(String newText) {
                /*if (isOtherRight) {
                    if (rusOtherAdapter != null) {
                        rusOtherAdapter.getFilter().filter(newText);
                    }
                } else {
                    if (otherRusAdapter != null) {
                        otherRusAdapter.getFilter().filter(newText);
                    }
                }*/
                return true;
            }
        });
    }


}

public class ItemAdapter extends RecyclerView.Adapter<ItemAdapter.ItemHolder> {

    private final int RUSOTHER = 1;
    private final int OTHERRUS = 2;
    boolean isSecondItem = false;
    ArrayList<Item> items;

    public ItemAdapter (ArrayList<Item> items) {
        this.items = items;
    }

    @Override
    public ItemHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View v;

        switch (viewType) {
            case RUSOTHER:
                v = LayoutInflater.from(parent.getContext()).inflate(R.layout.item, parent, false);
                break;
            case OTHERRUS:
                v = LayoutInflater.from(parent.getContext()).inflate(R.layout.item, parent, false);
                break;
            default:
                v = LayoutInflater.from(parent.getContext()).inflate(R.layout.item, parent, false);
        }
        return new ItemHolder(v);
    }

    @Override
    public void onBindViewHolder(ItemHolder holder, final int position) {
        int type = getItemViewType(position);

        switch (type) {
            case RUSOTHER:
                RusOther rusOther = (RusOther)items.get(position);
                holder.txtWord.setText(rusOther.getWord());
                break;
            case OTHERRUS:
                OtherRus otherRus = (OtherRus)items.get(position);
                holder.txtWord.setText(otherRus.getWord());
                isSecondItem = true;
                break;
        }
    }

    @Override
    public int getItemViewType(int position) {
        int type = items.get(position).getItemType();
        if (type == 1) return RUSOTHER;
        else return OTHERRUS;

    }

    @Override
    public int getItemCount() {
        return items.size();
    }

    class ItemHolder extends RecyclerView.ViewHolder {
        public final TextView txtWord;

        ItemHolder(View itemView) {
            super(itemView);
            txtWord = (TextView) itemView.findViewById(R.id.txtWord);
        }
    }
}

public interface Item {
    int getItemType ();
}