What does the initialKey parameter do in the Pager constructor

Question

I am trying to understand what the initialKey does in the Pager constructor, but I cannot find any sort of explanation, not even in the official documentation:

https://developer.android.com/reference/kotlin/androidx/paging/Pager#%3Cinit%3E(androidx.paging.PagingConfig,%20androidx.paging.Pager.Key,%20androidx.paging.RemoteMediator,%20kotlin.Function0)

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Can anyone explain what it does or how it works and how to use it?

Supernumerary

developer.android.com/reference/kotlin/androidx/paging/… Seems to be the page you want to start the pagination from. null by default – Aloin

@Aloin Thanks, but it is not clear what it refers to nor how it can be used. Is it the number of a page to load directly, the number of the items' position in the paged list, etc. – Supernumerary

Answer 1

After testing I believe the initialKey param is meant to indicate a position in the list, not a page.

I did two tests with varying page sizes.

Table with 2000 entries

Page sizes

• 10
• 20
• 100
• 123

For each page size I used the following as the initialKey for an item at position X

• initialKey = X
  • this uses the item position as the initialKey
• initialKey = X / page size
  • this uses the page in which the item is part of

For all results the item would always be correctly loaded in the initial/first chunk of data when I used the initialKey = X. It always failed when I used it as page size.

I am not sure if this is conclusive, but this was my conclusion from the limited tests for my problem.

Supernumerary