Created
September 16, 2017 18:53
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Shows how a RoomDatabase.Callback can be used to add database triggers when a database is created.
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@Database(...) | |
abstract class AppDatabase : RoomDatabase() { | |
abstract fun appDao(): AppDao | |
companion object { | |
private var INSTANCE: AppDatabase? = null | |
private set | |
fun getInMemoryDatabase(context: Context): CCDatabase { | |
if (INSTANCE == null) { | |
INSTANCE = Room.databaseBuilder(context, | |
AppDatabase::class.java, "app_database.db") | |
.addCallback(CALLBACK) | |
.build() | |
} | |
return INSTANCE!! | |
} | |
private val CALLBACK = object : RoomDatabase.Callback() { | |
override fun onCreate(db: SupportSQLiteDatabase) { | |
super.onCreate(db) | |
db.execSQL("CREATE TRIGGER ...") | |
} | |
} | |
} | |
} |
@carstenhag Your code snippet of handling singleton is missing the critical part of assigning the newly created object to the INSTANCE variable. Perhaps you could write .also {INSTANCE = it}
at the end.
Can I use INSTANCE in callback? Because I want to put some initial data which has to be added only once. If yes, is there any possibility to implement such with Dagger Hilt?
if you meant like pre-populating your db, for sure you can do that in here. i am not sure about Dagger Hilt, though.
Thanks a lot! i was looking for that solution :D
private val CALLBACK = object : RoomDatabase.Callback() {
override fun onCreate(db: SupportSQLiteDatabase) {
super.onCreate(db)
db.execSQL("CREATE TRIGGER ...")
}
}
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Thanks a lot @AdamMc331!
The callback has to be saved as a variable, declaring it inside the callback didn't execute it at all for me.
The Kotlin way to handle the
INSTANCE
singleton would be like this: