I have an application with prefilled database (I use Room, Kotlin). Database class:
@Database(
entities = [FurnitureModel::class, ImageModel::class],
version = Database.VERSION,
exportSchema = true
)
abstract class Database : RoomDatabase() {
abstract val furnitureDao: FurnitureDao
abstract val imageDao: ImageDao
companion object {
const val NAME = "application-data"
const val VERSION = 3
@Volatile
private var instance: Database? = null
fun getInstance(context: Context): Database {
synchronized(this) {
var inst = instance
if (inst == null) {
inst = Room.databaseBuilder(
context.applicationContext,
Database::class.java,
"$NAME-local.db"
)
.fallbackToDestructiveMigration()
.createFromAsset("$NAME.db")
.build()
instance = inst
}
return inst
}
}
}
}
It worked fine. Once I decided to update some data inside database. No stucture changes, just adding and changing some data. For versions, I changed constant VERSION from 3 to 4. When I run the application, I've got empty database. As I understand, it is possible to get empty database with fallbackToDestructiveMigration in few situations. I could made some mistake somewhere in data. To get more details I decided to run application without preinstalled previous version. Clean install, if I can say like this. To do it, I wiped data for Virtual device in AVD Manager, removed build directories in application and app directories and run 'Invalidate cache/restart...' in Android Studio (I know that there is no need to do it). But the result is always the same: trying to install my application I always get error
Caused by: java.lang.IllegalStateException: A migration from 3 to 4 was required but not found. Please provide the necessary Migration path via RoomDatabase.Builder.addMigration(Migration ...) or allow for destructive migrations via one of the RoomDatabase.Builder.fallbackToDestructiveMigration* methods.
As I understand, the error must not be shown when you install the application for the first time. But it is shown. I tried to create new virtual device and run app there, but the error is still there. What should I do to forse Android Studio to forget that the application was installed before? Thank you.
UPD1: I don't need to keep any data, actually I want to delete all data from previous versions of application. But after wiping data it still works as if I didn't wipe it. This is the problem.
RESULT: I found that the problem was in prefilled database. Unfortunatedly I can't find that is exactly wrong with database. I disabled creating database from assets, run application so that Room created bew empty database, copied the database from emulator and compared each table with my database. No any difference. So to solve the problem I just moved all data in each table to the same table in new empty database (using DataGrid). After running the application new database the problem disapeared.
