public class LoginActivity extends AppCompatActivity {

    private   LoginViewModel loginViewModel;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        ActivityLoginBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_login);
        loginViewModel = ViewModelProviders.of(this).get(LoginViewModel.class);
        binding.setLoginViewModel(loginViewModel);
        binding.setLifecycleOwner(this);

        loginViewModel.user.observe(this, new Observer<User>() {
            @Override
            public void onChanged(@Nullable User user) {
                Toast.makeText(getApplicationContext(), user.toString(), Toast.LENGTH_LONG).show();
            }
        });

    }
}

public class LoginViewModel extends ViewModel {

    private LoginRespository loginRespository = new LoginRespository();
    public MutableLiveData<User> user = new MutableLiveData<>();

    public MutableLiveData<String> email = new MutableLiveData<>();
    public MutableLiveData<String> password = new MutableLiveData<>();

    public LoginViewModel() {}

    public void onLoginClicked() {
        user = loginRespository.doLogin(email.getValue(), password.getValue());
    }

}

@Singleton
public class LoginRespository {
    private APIInterface apiInterface;

    public LoginRespository(){
        this.apiInterface = APIClient.getClient().create(APIInterface.class);
    }

    //private final APIInterface apiInterface;
    /*@Inject
    public LoginRespository(APIInterface apiInterface) {
        this.apiInterface = apiInterface;
    }*/

    public MutableLiveData<User> doLogin(String email, String password) {
        final MutableLiveData<User> data = new MutableLiveData<>();

        Call<User> call = apiInterface.doGetLogin(email, password, APIClient.X_API_KEY, APIClient.X_CLIENT_ID);
        call.enqueue(new Callback<User>() {
            @Override
            public void onResponse(Call<User> call, Response<User> response) {
                User user = response.body();
                Log.d("#####0", user.toString());
                if (user.code.equals(APIClient.Codes.OK)){
                    Log.d("#####1", user.toString());
                    data.setValue(user);
                    Log.d("#####2", data.toString());
                }
            }

            @Override
            public void onFailure(Call<User> call, Throwable t) {
                call.cancel();
            }
        });

        return data;
    }
}

public class User{

    @SerializedName("code")
    @Expose
    public String code;
    @SerializedName("data")
    @Expose
    public List<Datum> data = null;
    @SerializedName("description")
    @Expose
    public String description;
    @SerializedName("datetime")
    @Expose
    public String datetime;

    /**
     * No args constructor for use in serialization
     *
     */
    public User() {
    }

    /**
     *
     * @param description
     * @param data
     * @param code
     * @param datetime
     */
    public User(String code, List<Datum> data, String description, String datetime) {
        super();
        this.code = code;
        this.data = data;
        this.description = description;
        this.datetime = datetime;
    }

    @Override
    public String toString() {
        return "User{" +
                "code='" + code + ''' +
                ", data=" + data +
                ", description='" + description + ''' +
                ", datetime='" + datetime + ''' +
                '}';
    }
}

public void onLoginClicked() {
    user = loginRespository.doLogin(email.getValue(), password.getValue());
}