Android MVVM: how to avoid multiple livedata triggers when data from network did not change

Question

I have this basic Android Architecture Component use-case where I observe a live-data and update UI.

 myLiveData.observe(viewLifecycleOwner, Observer {
     // update UI
 })

 // will trigger a network call and update the repository (Room DB)
 myViewModel.refreshDataFromRepository()

With the observe call, I get the trigger and I update the UI, which is fine. However, I also need to update the DB if the backend data has changed, so I trigger a network refresh and that updates the DB and triggers the observer once again. So, I am getting data twice.

I can change conflict strategy to ignore to avoid but I need to set it to "replace" as the data may change:

@Query("SELECT * FROM my_table ORDER BY timestamp DESC")
fun getMyEntities(): LiveData<List<MyEntity>>

@Insert(onConflict = OnConflictStrategy.REPLACE)
suspend fun add(myEntity: MyEntity)

Other option is to compare the network response with DB contents and avoid re-writing identical data but would be expensive.

Is there any way, database access can be made intelligent to avoid trigger if data has not changed?

Answer 1

You could use distinctUntilChanged, it has been added to Transformations:

myLiveData.distinctUntilChanged().observe(viewLifecycleOwner) {
     // update UI
 }