Provide a better API for sticky headers in paging-compose [193785330]

Assigned

Feature Request

Status Update

No update yet.

Description

du...@google.com

created issue #1

Jul 15, 2021 03:23PM

Currently, the only way to use stickyHeaders with Paging is of the following form:

fun foo(items: LazyPagingItems) {
  for (i in 0 until items.itemCount) {
    if (items.peek(i) is String) {
      stickyHeader {
      }
    } else {
      item {
      }
    }
  }
}

This has the drawback of being unaware of what items changed, so we need to iterate through the entire list to figure out where to add sticky headers.

It would be desirable for paging-compose to provide an API that allows incremental computation, caching results from items that have not changed.

In the case of using sticky headers as "separators" it may make more sense to provide the item before and after, similar to .insertSeparators on PagingData.

Currently stickyHeader is still an experimental API, but before it goes stable we should make sure we have a good story for compatibility with Paging.

Comments

ru...@futured.app <ru...@futured.app> #2Nov 23, 2021 09:48AM

Hello, can you please attach a sample that reproduces your error?

du...@google.com <du...@google.com> #3Nov 23, 2021 07:23PM

I’ve attached two screen recordings demonstrating the mediator's behavior during the first and second launches after installation. Additionally, https://gist.github.com/yatiksihag01/20106aa4855bd438e3eb982034d4bb7d is link to a GitHub Gist containing the code for my remote mediator file for your reference.

ru...@futured.app <ru...@futured.app> #4Nov 24, 2021 08:19AM

Based on first_launch_after_installation.mp4, your paging state is indeed showing null for nextKey, so it makes sense that Paging concluded there are no more items to load.

So I think the question is why the PagingState contains only an empty page and null values. My guess is either

RemoteMediator REFRESH actually returned empty data - what is the returned allNewsItems value on initial REFRESH?
RemoteMediator REFRESH successfully loaded data and inserted it into database, but Paging hasn't processed that yet by the time Append is triggered, so PagingState is empty.

The second case doesn't seem likely though.

If you attach an executable app, I can look into this further.

Otherwise, you may gain more insight through Paging logs with adb shell setprop log.tag.Paging VERBOSE. You can also try implementing RemoteKeys in this codelab which addresses possible races between Refresh and subsequent loads.

cl...@google.com <cl...@google.com> May 1, 2023 10:15PM

Reassigned to cl...@google.com.

vo...@gmail.com <vo...@gmail.com> #5Jun 12, 2023 10:26AM

Hey! I ran into this same issue. It is in fact the second case you mentioned and is documented here.

I've published a repo reproducing the issue and filed a ticket proposing how this could be changed.

ja...@veeva.com <ja...@veeva.com> #6Aug 18, 2023 09:38AM

I am having the same issue adding stickyHeaders on LazyPagingItems, we have to iterate overall the items, and this can only cause bad performance and potential out-of-memory crash...

ma...@molo17.com <ma...@molo17.com> #7Nov 20, 2023 01:40PM

fe...@molo17.com <fe...@molo17.com> #8Nov 20, 2023 01:46PM

dm...@gmail.com <dm...@gmail.com> #9Mar 28, 2024 04:56PM

in...@gmail.com <in...@gmail.com> #10Apr 1, 2024 11:29AM

lv...@hubspot.com <lv...@hubspot.com> #11Apr 3, 2024 06:45PM

ti...@gmail.com <ti...@gmail.com> #12May 8, 2024 08:48PM

All workarounds result in loss of smooth animation when scrolling slowly. It looks like the list (elements of LazyColumn) is jumping in tiny steps. Not applicable

ma...@gmail.com <ma...@gmail.com> #13May 28, 2024 02:24PM

+ 1

pe...@gmail.com <pe...@gmail.com> #14Aug 30, 2024 10:50AM

If you enable placeholders this will also break. The list will suddenly transform into a placeholder list which is bizarre.

cl...@google.com <cl...@google.com> #15Sep 4, 2024 10:10PM

comment#14 can you please file a separate bug and attach a sample project? Thanks.

sa...@gmail.com <sa...@gmail.com> #16Dec 9, 2024 01:45PM

Is this in progress anyway?

go...@yougotagift.com <go...@yougotagift.com> #17Dec 10, 2024 08:57AM

Is there any progress on this? This is a legitimate problem :(