Hey guys, this is not really kotlin specific but I have a weird issue with a shared viewmodel betwee...

# android

[Gilles Braun]

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?

[ruialonso]

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

[Gilles Braun]

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

[ruialonso]

ok, I thought that problem was fragment observer many times

[Gilles Braun]

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

[ruialonso]

but activity receives observable first time at least, no?

[Gilles Braun]

yes

[ruialonso]

any other changes activity doesn't?

[ruialonso]

😐

[Gilles Braun]

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

[ruialonso]

wow

[Gilles Braun]

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

[ruialonso]

are you using a ViewModelProvider or koin to share viewmodel?

[Gilles Braun]

ViewModelProviders

[ruialonso]

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

[Gilles Braun]

thanks for your time 🙂

[ruialonso]

seems like SingleLiveEvent that don't propagate to more observers

[ruialonso]

I don't know

[Gilles Braun]

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.

[Gilles Braun]

It works now when I instantiate it like this:
ViewModelProviders.of(getActivity()).get(..)

[ruialonso]

jaja just this

[ruialonso]

fine 😄

[ruialonso]

have you tried koin? is simple to share viewmodel and provide them

[Gilles Braun]

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

[Grygorii Shcherbiak]

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