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Fix crash on scroll position restoration #1606

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Oct 17, 2023
Merged

Fix crash on scroll position restoration #1606

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2 changes: 1 addition & 1 deletion redwood-lazylayout-view/src/main/kotlin/app/cash/redwood/lazylayout/view/ViewLazyList.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -107,7 +107,7 @@ internal open class ViewLazyList private constructor(
val viewsOnScreen = recyclerView.children.map { recyclerView.getChildViewHolder(it).bindingAdapterPosition }
userHasScrolled = true // Prevent guest code from hijacking the scrollbar.
onViewportChanged?.invoke(
viewsOnScreen.min(),
viewsOnScreen.min().coerceAtLeast(0),
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.min() sometimes returns -1 (which had been observed / is expected)

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-1 is NO_POSITION which is what is returned for all positions between adapter invalidations and the next layout pass.

Also min and max throw if the sequence is empty, are we assuming the scroll callback will never be invoked on an empty list?

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@jingwei99 jingwei99 Oct 18, 2023 •
edited
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Also min and max throw if the sequence is empty, are we assuming the scroll callback will never be invoked on an empty list?

ahhh 🤔, that's the case (not invoked on empty list) so far (this has only only been applied to emoji search). But it's not guaranteed the invocation wouldn't happen on an empty list (someone else might use it, or other teams might use it).

-1 is NO_POSITION which is what is returned for all positions between adapter invalidations and the next layout pass.

👍

viewsOnScreen.max(),
)
}
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