How to populate Android Room database table on first run?

Question

In SQLiteOpenHelper there is a onCreate(SQLiteDatabase ...) method which i used to populate database tables with some initial data.

Answer 1

There are 3 ways of prepopulating of db
The first 2 is coping from assets and file which is described here
The third way is programmatical after db creation

Room.databaseBuilder(context, Database::class.java, "app.db")
    // ...
    // 1
    .createFromAsset(...)
    // 2
    .createFromFile(...)
    // 3
    .addCallback(DatabaseCallback())
    .build()

Here is the manual filling

class DatabaseCallback : RoomDatabase.Callback() {

    override fun onCreate(db: SupportSQLiteDatabase) = db.run {
        // Notice non-ui thread is here
        beginTransaction()
        try {
            execSQL(...)
            insert(...)
            update(...)
            delete(...)
            setTransactionSuccessful()
        } finally {
            endTransaction()
        }
    }
}