New to compose but I expected something like this to work bu

Question

New to compose but I expected something like this to work but it does not My activity has a field myTodoList mutableListOf lt String gt and it has items added to it by another source right now I have a post delayed handler that waits for 5 seconds and then adds ten items and I expect the items to update this Screen composable but nothing shows I m assuming it s because the state can t live in the activity That actually doesn t really make sense I guess Just want someone to look this over Thank you ``` Composable private fun MyActivityScreen items List lt String gt val myThings = remember mutableStateOf items Column myThings value forEach Text text = it ```

allan.conda · Answer

`myThings` is not necessary I think Use `items` directly

Kane Shih · Answer

LiveData observeAsState

Colton Idle · Answer

< allan conda> using items directly didn t work

Colton Idle · Answer

< Kane Shih> Do I have to use LiveData What if that s a dependency that I don t want to pull in and I just want to do this with pure compose

Kane Shih · Answer

1 find a way to call `myThings setValue` 2 Kotlin Flow or RxJava gt to State

Colton Idle · Answer

Hm So I need to use Flow or Rx to use compose

Kane Shih · Answer

or find a way to trigger recomposition

Kane Shih · Answer

but I think LiveData is still the best choice in your use case

Colton Idle · Answer

That s what I thought `val myThings = remember mutableStateOf items ` is used for < Leland Richardson G > am I doing something wrong here

flosch · Answer

Your problem lies not in compose but with your list in your activity The list needs to be observable if you want your composables to recompose on a change of the items in the list Either use a Flow lt List gt LiveData lt List gt or mutableStateOf List hand that over to your MyActivityScreen and observe it in there

Colton Idle · Answer

< flosch> so in my activitiy the field is defined as ```val listOfItems = mutableListOf lt String gt ``` so if I just change that to mutableStateOf I should be good I will try that now and let you know what happens Thank you I was not aware that I couldn t just use a regular list and pass it into a composable and then that composable converts it to an observable aka thats what I thought I was doing with my `val myThings = remember mutableStateOf items ` statement

flosch · Answer

Yes that is what it does but only in your composable scope If you change the value of `myThings` then it will be recomposed but you said you changed `items` outside of your composable that will not work

Colton Idle · Answer

Oooh Okay yeah that makes sense Let me give it a shot Appreciate your time and explanation < flosch>

Colton Idle · Answer

< flosch> still does not trigger a recomposition it seems Here is the composable ``` Composable private fun MyActivityScreen items MutableState lt MutableList lt String gt gt Column items value forEach Text text = it ``` And my activity defines a field ```val listOfItems = mutableStateOf mutableListOf lt String gt ``` and I add to the listOfItems via ```listOfItems value add adsf ```

flosch · Answer

Yea you will probably have to change the value of `MutableState` and not of the `MutableList` ```val listOfItems = mutableStateOf listOf lt String gt Composable private fun MyActivityScreen items State lt List lt String gt gt Column items value forEach Text text = it listOfItems value = listOf a listOfItems value = listOf a b ``` You could also use `mutableStateListOf` <https developer android com reference kotlin androidx compose runtime package summary mutablestatelistof|LINK>

Colton Idle · Answer

< flosch> That worked So basically mutable state can t use a mutable class obj reference Wish there was a lint check for that maybe Also wish there was an easy way to take a list and copy or duplicate it To get around it for now I started doing list toMutableList then call add new value then toList Seems inefficient

flosch · Answer

```data class State val items List lt String gt val state = state copy items = ``` Immutable objects are the way to go with data driven architectures

Colton Idle · Answer

Oooh So just wrap it in a data class Okay I just thought it was interesting there was no copy on a List thumbsup Thank you < flosch>