Very simple question. Dashboard screen has a Text,...

# compose

[Android75]

Very simple question.
Dashboard screen has a Text, viewModel get data from db and so change string in Text.

@Composable
fun DashBoardScreen(viewModel: DashBoardViewModel) {

    var dashBoardState = viewModel.uiState.collectAsState().value
    Text(text = "Title ${dashBoardState.title}" )
viewModel.loadData()

// ViewModel
val uiState = MutableStateFlow(DashboardState(false))

   private fun loadData() {
     uiState.value = uiState.value.copy(
            title = "Text Changed" )
    }

i don’t know why Text doesn’t change string…

[Lisandro Di Meo]

I think you should remove the .value at val dashboardState = viewmodel...

[Android75]

no doesn’t work

[Android75]

ok how can you change value text in compose screen from viewModel?

[Lisandro Di Meo]

You have multiple alternatives... The most straightforward is having a livedata to observe as state from your composable

[Lisandro Di Meo]

@Composable
fun Screen(viewModel: DashBoardViewModel = viewModel()){
   val uiState = viewModel.uiState.observeAsState()
   Text("Title: ${uiState.title}")
}

[Lisandro Di Meo]

also, you are using flows, and the way to "change" a flow is emitting values to it

[Android75]

i’d like use flow

[Lisandro Di Meo]

you can not just override its value

[Lisandro Di Meo]

its okay, you can use flows, but in order to do so, you must use emit

[Android75]

ok do you have some example 🙂 ?

[Lisandro Di Meo]

I haven't use stateflow much, but maybe something like this? (perhaps someone may correct me)

// inside your viewmodel
var x: MutableStateFlow<Int> = MutableStateFlow(0)

fun emitOne(){
   viewModelScope.launch { x.emit(1) }
}

[Android75]

thanks

[Lisandro Di Meo]

hope that helps

[dorche]

It's fine to write to a StateFlow using .value too

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

MutableStateFlow has a writable var property that’s meant to be written to – you don’t need to emit on a state flow, and i don’t think it makes any sense to do so. If that’s the behavior you need, you want MutableSharedFlow, not MutableStateFlow.

And as to whether to use .value after collectAsState or not, if you’re reading the value in the composition anyway, as is being done in this case, it doesn’t matter as far as compose is concerned.

The only thing about the code in the OP that looks wrong to me is that it calls viewModel.loadData() directly in the composition. That is a side effect, and should be done in an effect handler (e.g. LaunchedEffect). But I don’t see how that would be causing the text not to update.

It looks like you posted a snippet of your actual code, and I’m guessing something else is wrong that’s causing the issue.

[Lisandro Di Meo]

Thanks for clarifying ! 👍 also I think Zach is right, something else should be causing the text not updating 🤔