How to query a Room database so it returns a single object?

Question

I'm using Room as my local database for my project. I have created a MovieDao interface:

@Dao
public interface MovieDao {
    @Query("SELECT * FROM movies ORDER BY title ASC")
    LiveData<List<Movies.Movie>> getMovies();

    @Query("SELECT * FROM movies WHERE id = :id")
    LiveData<Movies.Movie> getMovie(int id);
}

Everytime I try to call getMovies() method, it correctly return a list of Movie objects but if I call getMovie(int id) and pass an id that exist for sure in the database I always get NPE.

Hoe can I create a query than can return a single Movie object?

Thanks!

Edit:

LiveData<Movies.Movie> liveData = movieRepository.retrieveFavoriteMovieTask(550);
liveData.observe(this, m -> {
    Log.d(TAG, m.title);
});

Error:

java.lang.NullPointerException: Attempt to read from field 'java.lang.String com.example.myapp.Movies$Movie.title' on a null object reference

Answer 1

id may be reserved by room. You can set a auto incrementing PK with @PrimaryKey(autoGenerate = true) then define your own id (movie_id) that you can set and get at will while leaving the PK integrity intact.