Hello :wave: Is there a way to intercept touch eve...

# compose

[Chris Johnson]

Hello 👋 Is there a way to intercept touch events such as ACTION_DOWN and ACTION_UP but still allow a LazyColumn to have ACTION_MOVE for scroll? My use case is: I want to allow a full screen list to scroll, but I want to do something when a finger is lifted up such as snap the list to a specific position

[Zach Klippenstein (he/him) [MOD]]

I believe the nested scrolling API gives you a hook for when scrolling transitions to fling

[Chris Johnson]

Hmn. Yeah there is onPre and onPost fling but really I only care about ACTION_UP. The user could be slowly scrolling my content and when they lift their finger up I want to snap the list into place. For context, I'm basically trying to re-create the default behavior we got from the MaterialCollapsingToolbar. I have a working implementation listening for when the scrollState's isScrollInProgress and that works to check when they've stopped scrolling, but that also causes a LOT of recompositions in a very large complex composable. So I'm trying to avoid that as it causes noticeable lag.

[Zach Klippenstein (he/him) [MOD]]

You can use derivedStateOf to avoid recomposing on every isScrollInProgress update.

[Chris Johnson]

Ah I didn't even think of that state. You're a life saver man. Thanks!

[Chris Johnson]

Works as intended and is way smoother