``` private val uiJob = SupervisorJob() val uiScope = CoroutineScope(Dispatchers.Main + uiJob) val j...

# coroutines

[Sergio Crespo Toubes]

private val uiJob = SupervisorJob()
val uiScope = CoroutineScope(Dispatchers.Main + uiJob)
val journeys = MutableLiveData<List<Journey>>()

fun loadJourneys() = uiScope.launch {
    val token = preferences.getProfileToken() ?: return@launch
    try {
        journeys.value = journeysService.getJourneys(token)
    }catch (e: Exception){
        showGenericError.value = Unit
    }
}

Hello i am trying coroutines with mvvm pattern. What i am doing bad with this? It´s working but the ui is blocked while is getting journeys. How can i fix this? Thanks.

[gildor]

How getJourneys is implemented? If your UI is blocked, than getJourneys is blocking function

[Sergio Crespo Toubes]

with suspend function

[Sergio Crespo Toubes]

retrofit call

[gildor]

Suspend function can be still blocking if implementation is not correct

[Sergio Crespo Toubes]

yes i think so

[gildor]

does it use standard retrofit suspend function support?

[gildor]

or it’s your own implementation?

[Sergio Crespo Toubes]

@GET("/api/me/journeys")
	suspend fun getJourneys(@Header(TOKEN) token: String): List<Journey>

[gildor]

also:

private val uiJob = SupervisorJob()
val uiScope = CoroutineScope(Dispatchers.Main + uiJob)

Can be replaced with:
val uiScope = MainScope()

[gildor]

Are you sure that you don’t have any nasty call adapters that may cause blocking? because it looks fine, nothing should be block.

Also, could you check does it work if you replace getJourneys() with delay(5000)?

[Sergio Crespo Toubes]

the problem of change MainScope to BackgroundScope is that i get an error assigning result of retrofit to mutablelivedata

[Sergio Crespo Toubes]

for modifying ui thread in background thread

[gildor]

yes

[gildor]

I understand

[gildor]

as I said, ecveryhing looks completely fine

[Sergio Crespo Toubes]

ok...

[gildor]

the problem of change MainScope to BackgroundScope

I do not suggesting this. Also MainScope() is just shortcut, it uses main dispatcher

[Sergio Crespo Toubes]

the block that i am talking about is with viewpager when i change with gesture the view

[Sergio Crespo Toubes]

the ui is blocked

[Sergio Crespo Toubes]

I will try MainScope()

[Sergio Crespo Toubes]

Thanks Andrey

[gildor]

Nono, It’s not a solution

[gildor]

I just said that you can write the same shorter

[Sergio Crespo Toubes]

ah XD ok

[gildor]

also you can just get main scope from lifecycle/lifecycleObserver.coroutineScope

[gildor]

About your original problem, try replace journeysService.getJourneys(token) with placeholder like delay(5000) and check, will your UI is still blocking or not

[Sergio Crespo Toubes]

ok

[Sergio Crespo Toubes]

I will test it this evening Andrey, i cant now. Thanks for all.