CODEWITHSUNDEEP
kotlinandroid-roomandroid-livedata
Marcel Fuchs
Marcel Fuchs

Reputation: 99

LiveData returns null value even though it contains a value

I have the following code:

class AddViewModel(application: Application) : AndroidViewModel(application) {

val readAllData: LiveData<List<DutyDay>>

private val repository: DutyDayRepository


init {
    val dutyDayDao = DutyDayDatabase.getDatabase(
        application
    ).dutyDayDao()

    repository = DutyDayRepository(dutyDayDao)
    readAllData = repository.readAllData

    val date = readAllData.value?.get(1)?.date
}

As you can see, readAllData is a LiveData List of type dutyDay. I'm fetching the data from Room Database, and this DB is not empty, I use it in my recyclerView, all works fine.

But when I try to retrieve the date from my dutyDay object in index 1 of my readAllData List (last line in the code example), that variable contains null when debuging, whereas it is clearly not null in the database and as shown in the recyclerView? (not visible in the example)...

What am I doing wrong?

Thanks for your help :-)

Upvotes: 0

Views: 875

Answers (1)

Brandon
Brandon

Reputation: 1427

Because LiveData is a life cycle aware component, it won't load any data until it has something observing it

So when its being loaded into your recyclerView, you would have observed/subscribed to it, so once the database has the value it would update the livedata and you would receive the value in the get() call as well

But what is happening here is your get() call is looking for the last value of your livedata object, which, due to not being observed, is null

Upvotes: 4

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