repo

public class MainViewModel extends AndroidViewModel {

private CurrencyRepository currencyRepository;
public final ObservableField<String> from = new ObservableField<>();
public final ObservableField<String> to = new ObservableField<>();
public final ObservableFloat value = new ObservableFloat();
private MutableLiveData<Currency> currencyLiveData;
String TAG = "MAIN";

public MainViewModel(Application application) {
   super(application);
   currencyRepository = new CurrencyRepository(application);
}

public void calculateRate() {
    currencyRepository.getCurrency(String.valueOf(from.get()), String.valueOf(to.get()), ApiClient.KEY);
}


public class CurrencyRepository {

private ApiInterface apiInterface;
private  String apiKey = ApiClient.KEY;

public CurrencyRepository(Application application) {
   apiInterface = ApiClient.getClient();
}

public LiveData<Currency> getCurrency(String base, String target, String apiKey) {

    final MutableLiveData<Currency> data = new MutableLiveData<>();
    apiInterface.getCurrentCurrency(base, target, apiKey).enqueue(new Callback<Currency>() {
        @Override
        public void onResponse(Call<Currency> call, Response<Currency> response) {
            data.setValue(response.body());

        }

        @Override
        public void onFailure(Call<Currency> call, Throwable t) {

        }
    });
    return data;
}