Hello! I am having troubles understanding how `rem...

# compose

[Grigorii Yurkov]

Hello! I am having troubles understanding how remember works, so I created this simple example.
Here, every time I click on Switch I get a new random number. AFAIU this happens because remember gets removed from the tree, so it forgets the value it remembered.
How can I get around it? I need something similar to the View.GONE that doesn't remove the node from the tree, but makes it non interactable.

[Stylianos Gakis]

Yeah you got it. When it leaves the tree completely, it can't still be remembered across compositions.
If you want it to persist, you must have it in a place where it does not leave the tree.
So just extract it to right above the if (bool) line.
So:

val text = remember { Random...}
if (bool) {
  Text(text = text)
} else {
  Text(text = text)
}

This would persist the text across recompositions, and even if bool changes back and forth

[Grigorii Yurkov]

Yes, I can extract, but it was just the simplest example I can provide.
Here is the more complex version. WebView gets reloaded every time I switch destination. This is what I am trying to avoid

[Stylianos Gakis]

Heh, we went from a simple example to the nuclear one quite quickly 😅
This reminded me of this thread https://kotlinlang.slack.com/archives/C04TPPEQKEJ/p1709791721938469 but I still feel like I don't have an answer for this myself.
I haven't used WebView myself so I've been lucky to avoid this issue 😄

[Grigorii Yurkov]

This question is not about WebView itself. I just used it so you cannot "cheat your way out" by extracting remember function 🙂

I just want to understand, can I remove a node from the tree without reseting remember or AndroidView

[Konstantin Tskhovrebov]

in that case you have to extract required state outside of the UI.
as I remember there is a webview client which can be declared externaly

[Grigorii Yurkov]

@Konstantin Tskhovrebov So, I have to use correctly scoped ViewModels so store the state. But what about Views themselves? They are not cheap to create. Should I implement my own view pool then?

[Konstantin Tskhovrebov]

It depends on you case. It is not typical scenario to use android views in compose scenes. So, if you want achieve a high performance in the case of show/hide android views then, I guess, yes, you may try to implement some caches

[MR3Y]

You might be interested in reading this thread: https://kotlinlang.slack.com/archives/C01D6HTPATV/p1719423595969549?thread_ts=1719415671.383299&cid=C01D6HTPATV
TL;DR use SaveableStateHolder which being utilized by most navigation libraries under the hood to save state for destinations that aren't currently visible but still exist on the backstack

[shikasd]

In the WebView case you could also try movableContentOf to preserve the state, but it can get funky when view gets involved.

[Trym Nilsen]

Sounds similar to my issue 😄 https://kotlinlang.slack.com/archives/CJLTWPH7S/p1709132135571379 I have not gotten around to it yet, but my plan was to keep a reference to it in the hosting activity and clean it up when the activity is destroyed