So in compose there is remember. Which basically avoids recomposition. So you also generally emit ...

# compose

[David Corrado]

So in compose there is remember. Which basically avoids recomposition. So you also generally emit that state to your VM via a callback. There are times where you have to update what is remembered by what is in the viewmodel. From my understanding a couple popular ways to do that is either not have remember but I have an issue with a control does not work well with many recompositions. Another way is remember(KEY). Where key is something that updates remember. Couple questions
1. Do you think if a control does not work well with many recompositions its a bug? Basically its the slider the thumb in Material compose
2. If you recommend using remember(key) to clear it how have you seen this architected. Feels a little hacky

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

remember doesn't avoid recomposition, it allows something to persist between recompositions.

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

1. Do you think if a control does not work well with many recompositions its a bug? Basically its the slider the thumb in Material compose

Are you saying you're seeing unexpected Material slider behavior?

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

It's hard to answer your very abstract question. There are plenty of valid use cases for using remember with a key, but it's also possible to misuse it. If you're deriving some value in a composable from your view model and remembering it, does it really need to be remembered if the view model is the source of truth?

[David Corrado]

I am not sure if its considered unexpected if on recomposition the thumb disappears

[David Corrado]

Like I am moving my finger along and the thumb disappears and also found thumb jumping around. So it sounds like on recomposition that is unexpected?

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

How are you storing and updating the slider value?

[David Corrado]

It is in the VM in uistate which is collectAsStateWithLifecycle

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

So when the slider change callback is invoked, you pass it to the VM, which eventually emits on a flow?

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

It's possible the update is happening asynchronously, which means the next frame after an input event the old slider value is still used.

[David Corrado]

Also my use case is. I have a slider. That when it moves it updates the main viewmodel single UI state. There is a checkbox that is outside of the composable that can reset the slider so it updates the VM and thus updates the slider.

[David Corrado]

So when the slider change callback is invoked, you pass it to the VM, which eventually emits on a flow?

Yes

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

That shape in general is fine, but if it's jumping around it sounds like something might be happening async

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

Are you using any flow operators?

[David Corrado]

Yeah I am exploring with a greenfield app to see if I can replicate it. So you are saying recomposition should basically not cause that thumb to disappear. I can dig into that

[David Corrado]

Are you using any flow operators?

No.

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

If you can reproduce in a new project, please share here and I can take a look

[David Corrado]

I had 2 issues that I am digging into
1. I believe changing the theme around the slider causes the thumb to disappear and do some really weird things
2. The thumb jumped around. I think this is due to a mishandling of the slider value I am doing. I can dig into this more
I am digging into these and will post with a project or what I find(if its not an issue)

[Alex Vanyo]

I’ve seen Slider state management have very similar characteristics to text fields that is explored in https://medium.com/androiddevelopers/effective-state-management-for-textfield-in-compose-d6e5b070fbe5

You can get really weird behavior if there’s any asynchronicity between the Slider changing the value, and when the value passed to the Slider updates, and a Flow in a ViewModel can definitely introduce that asynchronicity

[David Corrado]

Thanks. Likely my issue. @Alex Vanyo you seen a more complicated github example where it handles multiple of these controls and passes it up and down multiple layers of composable in a clean way

[dazza5000]

Not sure if this is related, but we logged something similar to this a while back https://issuetracker.google.com/issues/311440479