在 Kotlin StateFlow 中使用发射

Question

Until now I was using Flow and mapping it to LiveData like below -

The MyService looks like this -

override fun provideData(action: MyAction) = flow {
   emit(MyResult.Loading)
   emit(dataRepository.getNewData())
}

The ViewModel looks like this -

fun getData() = myService.provideData(MyAction.GetData).map {
                
}.asLiveData(Dispatchers.Default + viewModelScope.coroutineContext)

I want to move to StateFlow . How can I use emit function with StateFlow like I used it with Flow .

Answer 1

You can write your flow as before, but replace .asLiveData(scope) with .stateIn(scope, SharingStarted.Eagerly, null) to get an instance of StateFlow running in the corresponding scope with a similar behavior that you were getting with LiveData before — sharing is started immediately and the initial value is null (just like with LiveData ).

You can read here for more details and explanation of all stateIn operator parameters here https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines.flow/state-in.html