IssueTracker

To be clear, when you say jump pages, do you mean recyclerview is scrolling down, or is viewpager scrolling across multiple fragments?

A repro / sample project demonstrating the issue would definitely be helpful here.

You also mentioned alph09 in the title, but alpha07 in the comment - could you specify which version of viewpager and paging you are using?

Ah sorry I see that you have used both here, still could you specify which version of viewpager you are using as well?

Haven't forgotten this - this is on my queue, just that my queue is quite long :)

This looks like a weird race scenario where the smooth scroll behavior in RV / ViewPager is attempting to do an animated scroll to an absolute position, but Paging is able to PREPEND items to the front of the list faster than the animation can scroll there.

I noticed that you're attempting to enablePlaceholders to mitigate this by telling Paging the total item count, but you never pass a value for placeholdersBefore / After in the initial result on REFRESH. This will prevent Paging understanding how many placeholder items there are in the list. This is probably something Paging should check for, but the proper solution to this ticket should probably be some kind of relative scrolling behavior on RecyclerView or ViewPager, however I expect boundary cases to be quite annoying to deal with there.

I'm closing this out since it's not a Paging issue, but I'm happy to continue the thread here to help you get a working solution.

The first thing to try would be to return some positive value for placeholdersBefore and placeholdersAfter in PagingSource.load() when LoadParams is of type LoadParams.Refresh. From here you'll need to know what the total number of items you want to show in your ViewPager is and add that boundary check to your next / previous buttons.

Placeholders are a count of the number of not-yet-loaded items in the dataset, which is returned by PagingSource.load() in LoadResult.Page(...)

You just need to set itemsAfter or itemsBefore and to display them, enablePlaceholders in PagingConfig.

You want to pass in the number of items in the full dataset that appear before the first item in data to itemsBefore and number of items that appear after the last item in data to itemsAfter

So if you had these items in your db: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

A sample LoadResult.Page with itemsBefore and itemsAfter set would be:

LoadResult.Page(
  data = listOf(4, 5),
  prevKey = 3,
  nextKey = 6,
  itemsBefore = 4,
  itemsAfter = 4
)

It doesn't make sense to pass a negative number to itemsBefore because it implies you've loaded data that shouldn't exist.

whenever i set itemsbefore or itemsafter it show me null value

Also i updated the logic inside here as well as library to stable version. https://github.com/vivek-modi/ViewPagerExample

For anybody about to add a "+1" comment: please don't; it just annoys subscribers to the issue and reduces the chance of getting a fix because it makes people want to unsusbscribe. Star the issue instead if you want to increase the count of people who want it fixed.

+1