Hey, composers! I have a question about composable...

# compose

[Yev Kanivets]

Hey, composers! I have a question about composable items reusability in LazyColumn / LazyRow. Basically, are underlying views in view hierarchy are ever reused for new views while scrolling? Or do they always created from scratch? RecyclerView created (onCreateViewHolder) views only for those which are on the first screen and reused them (onBindViewHolder) when scrolling.

[Yev Kanivets]

I've done a quick investigation of the LazyList source code, but there I was able to find only the visible views calculations, which need to be displayed. But no hints on reusability of already allocated views.

[Bradleycorn]

My guess is no.
Compose does not use views (even at a low level), or even anything that is conceptually similar. That’s part of what makes it so efficient. It draws content directly on the screen.
So, for Lazy* composables, there is nothing to “reuse”. Instead, as the user scrolls, the list is re-composed, and it figures out which `item {}`’s should be rendered and it measures and places (renders) those items.
I haven’t looked closely at the code myself, but that’s my understanding of how the Lazy* composables work.

[Albert Chang]

Actually there is some kind of reuse. Not "view" though. See this.

[Bradleycorn]

ah interesting

[Colton Idle]

I think originally there was no reuse, and then the reuse was added pretty late IIRC.

[Colton Idle]

but yeah, there were a few really good threads/reads here from Andrey.