It seems like if there was not a user interaction i e updati kotlinlang #compose

It seems like if there was not a user interaction (i.e. updating initial state from the server instead of a user action) the values don’t update. I use the same model for different controls and some work / some don’t.

Leland Richardson [G]

06/23/2020, 11:08 PM

just a shot in the dark, but usually when i see people run into this problem it’s because you’re actually creating a new model/state every time you recompose. For instance:

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@Composable fun Counter() {
  var count = mutableStateOf(0)
  Text("Count: ${count.value}")
  Button(onClick={ count.value++ }) {
    Text("Increment")
  }
}

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👍 1

ie, what you really want is:

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@Composable fun Counter() {
  val count = remember { mutableStateOf(0) }
  Text("Count: ${count.value}")
  Button(onClick={ count.value++ }) {
    Text("Increment")
  }
}

which is the same as

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@Composable fun Counter() {
  val count = state { 0 }
  Text("Count: ${count.value}")
  Button(onClick={ count.value++ }) {
    Text("Increment")
  }
}

so perhaps you’re constructing a model each recompose and you’re only seeing the initial state each time

gildor

06/24/2020, 1:42 AM

Had the same issue when just started play with compose. Should usage of eager version of mutable state be discouraged?

state { defaultValue }

even shorter and avoid such accidental introduction of state recreation Or there is some important use case for mutableStateOf?

Leland Richardson [G]

06/24/2020, 2:05 AM

mutableStateOf can be used outside of composition, which is an important use case. This is a common source of confusion though so we are throwing around ideas of how to make it less likely to make this mistake

gildor

06/24/2020, 2:21 AM

ahh, right, so state is composable itself and cannot be called outside of composable function

Maybe lint check? because usage of it from composable function most probably a mistake

Leland Richardson [G]

06/24/2020, 3:01 AM

yep, this is at a minimum something we will do

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