Is there a way to control the “offset” of a `LazyR...

# compose

[Tgo1014]

Is there a way to control the “offset” of a LazyRow ? The idea would be to manually controle the LazyRow position to sync the scroll when dragging a pager

[Albert Chang]

There is scrollToItem().

[Tgo1014]

With scrollToItem() it moves directly but the idea is to sync the drags to move together

[Albert Chang]

That's what you use to control the offset. If you want to sync it with another one then put it in a LaunchedEffect.

[Tgo1014]

But then in this case I’ll move just after the item is selected in the other Row, the idea is when you scroll one the other moves together even in between the items. This is possible with the Row using a Modifier.offset but this doesn’t work with a LazyRow.

[Albert Chang]

Why do you think it’s not possible to sync the offset when scrolling the other one?

[Tgo1014]

I guess I’m not explaining correctly the idea, let me get a video of it working with Row now.

[Tgo1014]

device-2022-04-05-122638.mp4

[Tgo1014]

So the bottom is a pager which provides the offset and the top one is a row. Using Modifier.offset we can move the items according to the pager offset but this via modifier doesn’t work for LazyRow . Any idea how to do it?

[Albert Chang]

I understand what you want and that’s why I told you to use LaunchedEffect.
Something like this should work:

LaunchedEffect(pagerState.currentPage, pagerState.currentPageOffest) {
    lazyListState.scrollToItem(pagerState.currentPage, pagerState.currentPageOffest)
}

[Tgo1014]

But the second param of scrollToItem is Int but pagerState.currentPageOffest is Float, so a 0.5 offset would be 0 as int

[Albert Chang]

Then round it to an int

[Albert Chang]

I believe you need to do some calculation anyway as items in the LazyRow and the Pager are not of the same width.

[Tgo1014]

You were correct. Adapting your idea a bit to the code worked fine. The final code looks like this:

LaunchedEffect(state.currentPageOffset) {
    scrollState.scrollToItem(
        state.currentPage, 
        state.currentPageOffset.times(itemWidthPx).toInt()))
}

Thanks a lot for the help 🙌🏽