*Is there anything like `RecyclerView`’s `StateRestorationPolicy.PREVENT_WHEN_EMPTY` for `LazyColumn...

# compose

[julioromano]

Is there anything like `RecyclerView`’s StateRestorationPolicy.PREVENT_WHEN_EMPTY for LazyColumn ?

LazyColumn doesn’t currently restore the scroll position if the list’s data is fed using something like val myList by aFlow.collectAsState(emptyList()).

For example during configuration changes (like rotation, dark/light theme switch, etc.) the flow will be resubscribed to and so aFlow will temporarily emit emptyList() causing the saved scroll position to be discarded.

This is a workaround I found but I was hoping it could be handled better:

if (myList.isNotEmpty()) {
    LazyColumn() {
       // .....
    }
}

[Ian Lake]

Generally, you should avoid the latency of requerying from scratch in the first place by using shareIn inside a ViewModel, thus ensuring that your last data is immediately available after a config change, skipping the whole empty list problem entirely

[julioromano]

Definitely, although ViewModel only helps for configuration changes but not for system initiated process death (SIPD).
I was looking for a solution that could encompass both.

Throwing in a ViewModel to optimize the configuration change part is always a nice to have and can be done with little effort.

In other words: if one solves the SIPD side, the configuration change side gets taken care of implicitly.

[Andrey Kulikov]

could you file a bug for this feedback? so at least we consider this in the future. but in general I don’t think the solution with if is that bad

[julioromano]

https://issuetracker.google.com/issues/179397301

[Albert Chang]

@Ian Lake
I don't think shareIn works because when using collectAsState() on flows other than `StateFlow`s you always have to specify an initial value and that initial value will always be used even if the flow emits immediately.
In my app I'm using collectAsState() on a flow produced by transforming the value of StateFlow in a ViewModel and I'm facing the same problem. I have tried shareIn and it didn't work.

[Ian Lake]

Sure, you can use stateIn then