So in order to retain state across activity recreation (activity process death and restoration) `sta...

# compose

[Archie]

So in order to retain state across activity recreation (activity process death and restoration) state would need to be store in

var someState by savedInstanceState<String?> { ... }

but what if the state is inside a LiveData and is accessed as

var liveDataState by liveData.observeState()

How could I put this liveDataState inside savedInstanceState?

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

Whatever owns the LiveData should be responsible for saving/restoring its internal state in that case. Otherwise, you’ve got two sources of truth.

[Archie]

hmmm... I'm sorry I'm so confuse. I still don't know what to do. Does that mean doing?

var liveDataState by liveData.observeState()
var someState by savedInstanceState { liveDataState }

SomeView(someState)

I'm really sorry about this.

[mattinger]

I think what he’s saying is that something is creating the “liveData” object. Whatever is creating that needs to have access to the SavedStateHandle so that whenever the value is written, the SavedStateHandle is updated.

[mattinger]

SavedStateHandle has a function to do this for you: savedStateHandle.getLiveData(key)

[mattinger]

if you’re unfamiliar with the saved state library, i suggest you read up on that, and this will make sense.

[Archie]

Yes that is true and would work really well with LiveData but how about Flow or Rx?

[Archie]

In this case is it correct to do:

class MyViewModel(
    val savedStateHandle: SaveStateHandle
): ViewModel {

    private val myMutableFlow = MutableStateFlow<String>("")
    val flow: StateFlow<String> = myMutableFlow

    private savedStateLiveData = savedStateHandle.getLiveData("MyKey")

    init {
        savedStateLiveData.observeForever { savedValue ->
            myMutableFlow.value = savedValue
        }
    }

    ....

    override onCleared() {
        savedStateLiveData.removeObservers()
    }

}