In this post I will show the method I used to add a predetermined set of values to an Android Room database at time of creation.
The project I was working on needed a list of strings for the user to choose from. The list needed to also be editable. The best option I chose was Room database. The issue was I needed to prefill the database with values when it gets created so the user already has options to choose from. This would give the user a better experience.
Below is the method I used to implement it.
Code
I put the values I wanted in an object class exposing a list.
object CategoryTypes {
val list: List<String> = listOf("Grocery", "Home", "Family", "Honey Do", "Work", "Bucket List", "Movies", "TV Shows", "Books", "Workout")
}Then inside the database helper that creates the Room database and provides the instance of it, I added a callback for the onCreate method.
@Database(
entities = [CategoryTable::class],
version = 1,
exportSchema = true
)
abstract class CategoryDatabase : RoomDatabase(){
abstract fun categoryDao(): CategoryDao
companion object {
// Singleton prevents multiple instances of database opening at the
// same time.
@Volatile
private var INSTANCE: CategoryDatabase? = null
fun getDatabase(context: Context): CategoryDatabase {
// if the INSTANCE is not null, then return it,
// if it is, then create the database
return INSTANCE ?: synchronized(this) {
val instance = Room.databaseBuilder(
context.applicationContext,
CategoryDatabase::class.java,
"category_database"
)
//start ----this is where the prefill happens
.addCallback(object: RoomDatabase.Callback(){
override fun onCreate(db: SupportSQLiteDatabase) {
super.onCreate(db)
db.beginTransaction()
val values = ContentValues()
val categoryTypes = CategoryTypes.list
categoryTypes.forEach {
values.put("category", it)
db.insert("categories", SQLiteDatabase.CONFLICT_ABORT, values)
}
db.setTransactionSuccessful()
db.endTransaction()
}
})
//end -------
.build()
INSTANCE = instance
// return instance
instance
}
}
}
}Hope this is useful.
