LiveData with Coroutines and Flow (Android Dev Summit '19)

[@saurabhsomani582]

This talk is my go to #1 talk from this channel. I keep coming back and always learn something new every time I rewatch and refactor my code.

[@adamhurwitz]

ViewModel - 10:45 Using .collect{ … } and .emit( … ) - 11:33 LiveData builder .asLiveData() - 11:45 .onStart{ ... } - 12:25 Replace LiveData switchMap - 13:00 Repositories - 13:20 Emit multiple values with flow{ ... } - 15:53 Working with non coroutine streams - 16:21

[@mochadwi]

thank you very much for this summary @Adam Hurwitz

[@ringoaikocascade]

Would like to talk about testing but we don't have much time - 17:22

[@yallam08]

This testing joke at the end is hilarious 😂

[@SociedadAndroide]

This was amazing !! Thank you guys now I know how to use flow :) Keep up the great work!

[@marlonlom]

Great review about livedata ando coroutines... After a year sharing similar topics

[@codingwithmitch]

Are there any samples on github?

[@RaymondChenon]

Sample with liveData. No Flow yet github.com/android/architecture-components-samples/blob/master/LiveDataSample/

[@TheHiddenAndroid]

Congrats to Yigit and Jose for a nice session! Just a bit silly that we have naming discrepancy in that we have lifecycleScope and viewModelScope but liveData {} is missing Scope suffix :/ And Jose, well done for lingering in the KZbin comments...

[@josealcerreca4841]

liveData launches a coroutine. The Scopes are just scopes that need `.launch` to launch the coroutine. Completely different things :)

[@igorg.8624]

Where are the Google samples for using Flow in android apps?

[@marlonlom]

codelabs (?)

[@theren8311]

codelabs.developers.google.com/codelabs/advanced-kotlin-coroutines/#0

[@marlonlom]

How can i unit test a method that contains a reference of a Flow thas is converted to a LiveData using the function 'asLIveData()' ????

[@bjugdbjk]

quite informative and lively presentation. I tried this scenario, Having a flow emitter in the datasource and taking into the livedata in the Viewmodel and question is when I am observing this livedata in the activity and when app goes to background and come back to the foreground, flow is restarting again and it's not getting paused?

[@benlu3523]

What a nice “Rx Java”

[@josealcerreca4841]

Nothing wrong with that!

[@robkeazor9709]

You mean Flow? because Livedata is pretty different than RxJava

[@cheesuscheetos4076]

Flow is a reactive component, it is indeed made as an answer to RxJava. One of the most beautiful things about Kotlin and JetBrains in general is that they really care about consistency and having in house solutions. For them having to use a third party library for something that they can implement themselves and is important is bad. This in turn makes the language feel syntactically consistent and a complete whole. Precisely this is the reason why so many of us love Kotlin. For me Kotlin Coroutines and Flow have so far been a complete hit that has addressed many problems and made concurrency, reactive programming and switching between threads so much more manageable, readable, understandable and easier.

[@preetgandhi1233]

@@robkeazor9709 Can you Please explain me the difference and when to use which? I am having a use case to fetch the Data from an API and show it in View no more UI to Database Interaction needed. So what should i use?

[@wahyukoco4562]

do we need to use live data instead of state flow in presentation layer?

[@tubun09]

is there any public repo example of this?

[@JoseAlcerreca]

We have a sample using the liveData builder but since Flow is experimental it'll take some time to be in official samples. github.com/android/architecture-components-samples/blob/master/LiveDataSample/

[@charlietapping4518]

@@JoseAlcerreca Would be really useful if you could just post a GIST of how you would replace the repository liveData coroutine builder with flow, using the typical Room response whilst the network updates the db in the background

[@josealcerreca4841]

We used Flow in the ADS app: github.com/google/iosched/blob/adssched/mobile/src/main/java/com/google/samples/apps/iosched/ui/sessiondetail/SessionDetailViewModel.kt

[@michaelnajera7958]

17:51 What is this "caching behavior" that we lose if we ditch LiveData and just use Flow?

[@yaroslavkulinich7155]

Livedata holds the last state. So if you unsubscribe from livedata and then subscribe again, you will receive the last emitted value. In case with flow, you always receive new value from fresh request.

[@michaelnajera7958]

​@@yaroslavkulinich7155 Thank you.

[@karibui494]

@@michaelnajera7958 you can just conflate the flow and it gets the same caching behaviour .

[@michaelnajera7958]

@@karibui494 I think I'd actually prefer not to get the cached value. To me, it violates the "single source of truth". But maybe I'm missing something. Is there a benefit to this default caching? All "caching" should come from my repository and not from something I don't control.

[@igorg.8624]

@@yaroslavkulinich7155 I believe RxJava PublishProcessor does this

[@lokthar6314]

Why would you use a WorkManager if you want to do a Http Request such as sending a tweet? (5:37)

[@lokthar6314]

@Ray If your App is doing a request while it's killed then this sounds like your App is not behaving right. App closed -> No requests, unless you do something like location tracking.

[@anupkunwar5290]

At 6:46 and 7:15 how can we retry the operation?

[@Rajmanov]

Super cool José!

[@KhairulImam10100]

I still having problem with testing my viewmodel that launches viewmodel corotuine scope and update livedata value inside that scope.

[@JoseAlcerreca]

This is covered in today's testing talk!

[@KhairulImam10100]

@@JoseAlcerreca Cool!! waiting for it!

[@alexneeky7920]

Why flow feels like rx java with extra steps?

[@benlu3523]

Because it is a flow (flowable)

[@dnkilic]

This is revolution!

[@petrushoc]

Awesome presentation

[@ViktorYakunin]

Flow APIs are very similar to Rx, what is next? adding library with extensions to clone all Rx functionality?

[@hinocenciopaulo]

Do you are pissed because your Rx knowledges are irrelevant right now?

[@ViktorYakunin]

@@hinocenciopaulo I'm using Kotlin in production since beta and Coroutines since experimental, so no. When you have a library (RxJava) that poisons all your codebase IMO its bad idea. But I must say that a lot of other technologies are on Rx stage, for example RxSwift, RxDart are there and Spring5 has async model as well that uses Rx too.

[@Muthuraj]

Flow is similar to Rx, but the major selling point for that is, it is multiplatform.

[@phamgiang9149]

An additional point is that RxJava is a heavy library. Most of the time, developers don't use 99% of its power in the codebase :D

[@igorg.8624]

@@Muthuraj Is there anybody doing this type of multiplatform in production?

[@marcopierucci4519]

How about retry option?

Any flow video tutorial?

[@help-ever]

Source code for the app will be available soon after I/O.

[@saungaye9717]

Imagine a life you don't know English much and try to understand this alien things.

[@NikhilMaurya10]

So livedata is also in the bin now. I like fast paced development but this is ridiculous.

[@JoseAlcerreca]

Not in the bin at all! (Data Binding, Java users) but we thought it was interesting to show. Remember we didn't create or control the development of Flow.

[@NikhilMaurya10]

@@JoseAlcerreca I guess it was bound to happen since popularity of Koltin was/is through the roof.

[@martinseal1987]

Where can I get that shirt

[@josealcerreca4841]

Limited edition :P

[@tellvivk]

My man

[@kyay10]

Lookin' good