What should I do if displaying a few items in a `LazyColumnI kotlinlang #compose

lags the screen for like 0.5 seconds when displayed? Is this perhaps because this is a preview, or do I have some way of profiling where the device spends its time?

Timo Drick

07/28/2020, 12:42 PM

It should not lag in any way. Maybe you are displaying very big images?

Fudge

07/28/2020, 12:45 PM

not images, just some text with some draggable modifiers

Timo Drick

07/28/2020, 12:46 PM

I think we need more information to help you. Can you provide some code?

Fudge

07/28/2020, 12:53 PM

there is quite a bit of stuff

I'll try to solve a problem I have now where

remember{}

doesn't remember at all and then try to simplify it

This is a very frustrating thing i've found about compose, because it doesn't use normal OOP semantics but instead hidden magics it's unclear when how or why something is saved in

remember{}

and the likes

Timo Drick

07/28/2020, 1:29 PM

for me val variable by state { } works most of the time better

And it will be deleted wenn the Composable is removed from the view

Fudge

07/28/2020, 1:35 PM

Is there a way to keep the state even when the composable is removed from the view? so that the state remains when you navigate back and forth

Timo Drick

07/28/2020, 1:40 PM

Yes just define the variable not inside of the view.

Copy code

var state by mutableStateOf(initialState)

Fudge

07/28/2020, 1:41 PM

I guess that's one way

Isn't

savedInstanceState

supposed to work too? If it survives process death it should survive switching views too

Timo Drick

07/28/2020, 1:42 PM

yes you are right. I did not used it yet because in the past it had many problems.

But now it should work as expceted

Fudge

07/28/2020, 1:43 PM

I tried

savedInstanceState

, seems like it doesn't work at all

Doesn't survive process death or switching views

Halil Ozercan

07/28/2020, 1:45 PM

remember

is confusing because it feels like it's supposed to remember a

variable

but it actually remembers the result of a calculation. So if your composable gets recomposed because of a dependency change,

remember

will trigger again but won't invoke the callback function. So if you've made changes to the local variable that was initialized by

remember

, it will get re-set by initially remembered value