Can't retrieve a simple string from SQLite

Question

I'm following the ViewModel app architecture for android, and run in to a problem when retriving some simple data from the SQLite database. Here are the simplified version of my DAO, and my repo:

THE DAO:

@Dao
public interface UserStuffDao {
    @Query("SELECT * from UserStuff")
    List < UserStuff > getAllUsers();

    @Query("SELECT path_to_user_profile_pic from UserStuff where id=:id")
    LiveData < String > getPathToUserProfilePic(Long id);
}

---

THE REPO:

public class UserStuffRepository {
    private static UserStuffRepository instance;
    private static UserStuffDao userStuffDao;
    public static final String TAG = UserStuffRepository.class.getSimpleName();


    public static UserStuffRepository getInstance(Application application) {
        Log.d(TAG, "[getInstance] called");
        if (instance == null) {
            instance = new UserStuffRepository();
            Database db = Database.getDatabase(application.getApplicationContext());
            userStuffDao = db.userStuffDao();
        }
        return instance;
    }


    public MutableLiveData < UserStuff > getUserStuff(Long id) {
        final MutableLiveData < UserStuff > userData =
            new MutableLiveData < > ();

        LiveData < String > info = userStuffDao.getPathToUserProfilePic(id);
        Log.d(TAG, "[getuserStuff] the dao returned ---> " + info.getValue());
        UserStuff to_return = new UserStuff(id, info.getValue());
        userData.setValue(to_return);

        return userData;
    }

    public void geteverything() {

        new AsyncTask < Void, Void, Void > () {
            @Override
            protected Void doInBackground(Void...voids) {
                Log.d(TAG, " EVERYTHING IN THE DATABASE " + userStuffDao.getAllUsers());
                return null;
            }
        }.execute();
    }
}

Problem is when I call the method getUserStuff(Long id) from the repo, (which then calls the method from the DAO), I get a null ( Log.d(TAG,"[getuserStuff] the DAO returned ---> "+info.getValue()); prints a null). I have a button that prints everything I have in the database, and there is clearly data in it, and the DAO should return something. Example:

Calling geteverything():

D/UserStuffRepository: EVERYTHING IN THE DATABASE [UserStuff{id=1, path_to_user_profile_pic='/path/path'}] 

Then calling getUserStuff(1) returns a UserStuff with an id of 1, and a pathToUserProfilePic of null.

Do you see any clear problem, or should I post extra stuff like initializing the repo, the ViewModel, and some stuff from the MainActivity? Thanks!

Answer 1

Change your function to return a simple String

LiveData<String> getPathToUserProfilePic(Long id);

To this

String getPathToUserProfilePic(Long id);

And of course change how you get it

String info = userStuffDao.getPathToUserProfilePic(id);
Log.d(TAG," [getuserStuff] the dao returned ---> " + info);

I'm pretty sure you don't need a LiveData there because you save the String to UserStuff.