Database_Impl doesn't exist - android app with Room

Question

I'm trying to use Room. I get this error (in runtime):

java.lang.RuntimeException: cannot find implementation for com.easythings.booky.database.BookyDatabase. BookyDatabase_Impl does not exist

My BookyDatabase class:

@Database(entities = [Book::class, Chapter::class], version = 1)
abstract class BookyDatabase : RoomDatabase() {
    abstract val bookDao: BookDao
    abstract val chapterDao: ChapterDao

    companion object {
        @Volatile
        private var _databaseInstance: BookyDatabase? = null

        fun getDatabase(context: Context): BookyDatabase {
            if (_databaseInstance == null)
                synchronized(BookyDatabase::class.java) {
                    if (_databaseInstance == null)
                        _databaseInstance = Room.databaseBuilder(
                            context.applicationContext,
                            BookyDatabase::class.java,
                            "booky_database"
                        )
                            .fallbackToDestructiveMigration()
                            .build()
                }
            return _databaseInstance!!
        }
    }
}

I don't understand what is wrong.

Answer 1

The BookyDatabase_Impl most likely isn't being generated ...

a) because you lack the annotations.

b) because you lack an annotation processor.

see Database or Defining data using Room entities .