VerticalScroller onScrollPositionChanged which was...

# compose

[Roar Gronmo]

VerticalScroller onScrollPositionChanged which was available in dev02 has disappeared in dev03. Do any have any clues how to read the VerticalScrollers postion now, or do we use another method to register scrollingchanges ?

[Adam Powell]

Use the ScrollerPosition hoisted state object, its value property is backed by @Model and reading it will trigger recomposition as needed

[Adam Powell]

note, this sample will be very slow right now but it will demonstrate 🙂

Column {
    val pos = +memo { ScrollerPosition() }
    Text("position: ${pos.value}")
    VerticalScroller(pos) {
        // content

(note: slow because it recomposes both the text and scroller per frame there and there's still a bunch of missing optimizations in this path; if you stick the text in a fixed size container it's much less so)

[Roar Gronmo]

Thanx @Adam Powell, do you know if there will be an "onEdgeOfList" trigger function (with some sort of displacement) to trigger loading of new elements in to the list in the future?

[Adam Powell]

Probably not in VerticalScroller as it's meant to be the ScrollView analog for smaller/less dynamic content. The `ListView`/`RecyclerView` analog is WIP at the moment and definitely will.

[Adam Powell]

But if you're looking for a way to do it with VerticalScroller today, you should have everything you need. Something like

val ScrollerPosition.isAtEndOfList: Boolean get() = value >= maxPosition - range

should do the trick

[Adam Powell]

and then using the usual model observation described above

[Adam Powell]

VerticalScroller composes its entire content body though, and given that you're also asking questions about integrating with database queries it's not intended to be the heavily scalable component for this sort of thing 🙂