Hey guys, this is not really kotlin specific but I have a weird issue with a shared viewmodel between an activity and fragment: The activity's observer is only executed once, whereas the fragment's observer is executed on every update. Any ideas why this might be?

set observe in Fragment at

onCreate

instead of

onViewCreated

. Fragment lifecycle is different from Activity and doesn't die, so every time Fragment is shown again it will handle observable from viewmodel even if no updates

I have the observers in

onStart

. Trying to observe the viewmodel in

onCreate

doesn't work as with the error

IllegalStateException: Can't access the Fragment View's LifecycleOwner when getView() is null i.e., before onCreateView()

. As far as I can tell the problem is not with the fragment, as it receives the updates correctly. But the activity doesn't

ok, I thought that problem was fragment observer many times

The fragment receives every update correctly, but the activity only the first

but activity receives observable first time at least, no?

yes

any other changes activity doesn't?

This is what the log outputs, people is the livedata:

observer called in fragment, people: 1
observer called in activity, people: 1
observer called in fragment, people: 2
observer called in fragment, people: 3
observer called in fragment, people: 4
observer called in fragment, people: 3

wow

it doesn't depend on the livedata itself either, because all other livedata's also only get 1 update when starting

are you using a ViewModelProvider or koin to share viewmodel?

ViewModelProviders

I'm sorry @Gilles Braun, have no idea why

thanks for your time 🙂

seems like SingleLiveEvent that don't propagate to more observers

I just found the problem, they were 2 separate viewmodel instances, not the same. The reason it always sent the first update is because Viewmodel initilizes its value.

jaja just this

This app has already Dagger implemented, so I would have to use that

if you have 2 separate instances of viewModel that might mean you have 2 fragments where you are supposed to have just one. And that is why switching to activity helps. I would suggest to check

this

pointers every time you hit a breakpoint in the LiveData observer and validate this