Kotlin Flow returned from Room does not update when an insert is performed from another Fragment/ViewModel

Flow returned from Room may not update automatically when insertions are made from other fragments or view models due to the cold nature of Flows. To continuously observe database changes and ensure updates in the UI, consider these solutions:

1. Convert Flow to LiveData (Option 1):

val count: LiveData<Int> = achievementRepository.getAllAchivements().map {
    it.count()
}.asLiveData()

This approach is demonstrated in Google's "Android Room with a View - Kotlin" Codelab.



2. Convert Flow to StateFlow (Option 2):

StateFlow is a hot stream that can be observed continuously using StateFlow.collect {}.



3. Ensure Singleton Instance of RoomDatabase:

Add @Singleton annotation to the provider of AppDB to guarantee a single database instance.



4. Call subscribeObservers() in onStart():

This ensures that observers are subscribed when the lifecycle starts, enabling updates.



5. Include Necessary Dependency:

implementation "androidx.lifecycle:lifecycle-livedata-ktx:2.2.0"

This dependency enables the conversion of Flow to LiveData in your code.



6. Use withTransaction Block for Inserts:

appDB.withTransaction {
    achievementDao.insert(achievement)
}

This ensures that the insert operation is executed within a transaction, potentially resolving update issues.



7. Enable Multi-Instance Invalidation:

Ensure that enableMultiInstanceInvalidation() is called when building the database to allow multiple instances to be invalidated.



8. Consider @Volatile for Database Instance:

Adding @Volatile to the database instance might prevent caching issues.