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

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.

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

1. RemoteMediator REFRESH actually returned empty data - what is the returned allNewsItems value on initial REFRESH?
2. 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.

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.

That makes sense to me if it's load from remote. Local source intended very short time to prepend/append, that's why UI flashing.

Then you should set TerminalSeparatorType.FULLY_COMPLETE instead of TerminalSeparatorType.SOURCE_COMPLETE.

SOURCE_COMPLETE means it will show footer and header once local sources is complete.

With TerminalSeparatorType.FULLY_COMPLETE, still flashing.

List updates in less than 100ms.

Logcat:

 Refresh l=[0, 1, 2]
      flow: 0 * 1 * 2
 Prepend l=[]
      flow: * 0 * 1 * 2

Are you trying to get the header and footer to show regardless of load state? i.e. Show footer and header even if there is more to load on either end?

This is what I'm trying to do:

 Refresh l=[0, 1, 2]
      flow: * 0 * 1 * 2        < Separator will appear in a very short time, so DON'T disappear here.
 Prepend l=[]
      flow: * 0 * 1 * 2

I have to collectLatest itemSnapshotList directly and add some delay to it. The spearator disappear and appear problem will be fixed. But not for first time load, because prepend only triggered after showing.

Separator will appear in a very short time, so DON'T disappear here.

It's not that the separator disappeared. The very first separator (the one before 0) is a TerminalSeparator and is inserted after prepend load returns endOfPagination = true.

So the sequence is:

Refresh l=[0, 1, 2]
insert separators after `0`, and `1`, resulting in [0 * 1 * 2]
Prepend l=[], endOfPagination = true
insert separator before `0`, resulting in [* 0 * 1 * 2]

So it seems like what you want is for the header and footer to show, regardless of whether there is more to load in that direction?

It's not just as a footer or header. Load state changes very fast, so in this case, the terminal separator flicking is very annoying.

So it seems like what you want is for the header and footer to show, regardless of whether there is more to load in that direction?

For boolean answer, Yes.