sqlite_to_room_db_init.kt

private val callback = object : RoomDatabase.Callback() {
  override fun onCreate(db: SupportSQLiteDatabase) {
    try {
      // First time to database was created, check if user upgraded from a previous
      // version of the app that was using ORMLite and migrate data if needed.
      val context = TradeMeApp.getContext()
      val previousDB = context.applicationContext.getDatabasePath(PREVIOUS_DATABASE_FILE)
      if (previousDB.exists()) {
        MigrateToRoom(previousDB, context.component.database).execute()
      }
    } catch (exception: Exception) { /* log error */ }
  }
}

@JvmStatic
fun getBuilder(context: Context): RoomDatabase.Builder<Database> {
  return Room.databaseBuilder(
      context,
      Database::class.java,
      DATABASE_FILE)
      .addMigrations(*migrations)
      .addCallback(callback)
}