Hi, When I update from compose `1.6.0-alpha01` to ...

# compose

[Osman Saral]

Hi, When I update from compose 1.6.0-alpha01 to 1.6.0-alpha02 my Pager is broken. The items are not loaded and the PagingData is not updated. I couldn't see any androidx.paging related change in the commits but maybe something else on the commit list causes this.

[Ian Lake]

Upgrading your Compose version does not upgrade your androidx.paging version - those are totally decoupled from one another

[Osman Saral]

ofcourse they are 🙂 but somehow my list is broken. I know it's very hard to tell what's wrong from the information I gave but I thought it would give you a hint. I didn't investigate further yet but what I know is when I update the compose, PagingData is not updated.

[Osman Saral]

I found out that there was a mistake on the ViewModel. Pager was created like this:

fun page(type: String) = Pager(
    config = PagingConfig(pageSize = 10),
    pagingSourceFactory = {
        TenantPagingSource(getTenantListUseCase, type)
    }
).flow.cachedIn(viewModelScope)

and collected like this:
viewModel.page("shop").collectAsLazyPagingItems()
This works with 1.6.0-alpha01 but doesn't work with 1.6.0-alpha02

When I fix it like this

val page = Pager(
    config = PagingConfig(pageSize = 10),
    pagingSourceFactory = {
        TenantPagingSource(getTenantListUseCase, "shop")
    }
).flow.cachedIn(viewModelScope)

or collect like this:

val shops = remember {
    viewModel.page("shop")
}.collectAsLazyPagingItems()

it works on the alpha02 too:

But I really wonder how it's related to the compose version.

[Ian Lake]

Sounds like your screen is recomposing - creating a new Pager every time your page function is called was only ever working by chance and was never how you should have had it set up

[Ian Lake]

It sounds like what you should be doing instead is having a MutableStateFlow to represent your type and using flatMapLatest on that flow to create the Pager and return the Flow from it, then cachedIn the result.

Then whenever your type changes, a new Pager and PagingSource gets created

[Ian Lake]

I don't know if changing type is even something you expect to happen? Generally, that would be a fixed value that you'd already have in your ViewModel (i.e., it would be an argument to your screen that would be automatically available via SavedStateHandle, so you wouldn't need to pass the type manually to your ViewModel ever

[Osman Saral]

Thank you for your recommendations @Ian Lake. There are only two fixed types, so I will just fix the bug by having two "pages" in my ViewModel. But it was really interesting to see that it was working before alpha02.