This talk was presented during the The Developer's Conference Florianópolis 2019 on Android Track, May 24th.

1. ANDROID JETPACK + COROUTINES:
TO INFINITEAND BEYOND
Ramon Ribeiro Rabello

2. Hi, I’m Ramon Rabello | Bio
11 years in Android
GDG Floripa Organizer
❤ Communities
Star Wars fan, I am!
Master Software Engineer |
about.me/ramonrabello
Beer lover

3. Come meet us! | ArcTouch Brasil at TDC
"Ask the Experts" Android session
Ramon & Paula - 13:10

4. Android Dev Generations™

5. Android Dev Generations | Looking back on Android history
Create Modern Apps with Android Jetpack
2008-2012 2013-2016 2017-…

6. Android Dev Generations | Looking back on Android history
Create Modern Apps with Android Jetpack
2008-2012 2013-2016 2017-…

7. Android Dev Generations | Looking back on Android history
Create Modern Apps with Android Jetpack
2008-2012 2013-2016 2017-…

8. Android Jetpack Recap

9. Android Jetpack | Overview
Simplify complex tasks
A collection of Android software components
Follow best practices
Free you from writing boilerplate code
Comprises the androidx.* packages

10. Android Jetpack | Overview
Simplify complex tasks
A collection of Android software components
Follow best practices
Free you from writing boilerplate code
Comprises the androidx.* packages

11. Android Jetpack | Overview
Simplify complex tasks
A collection of Android software components
Follow best practices
Free you from writing boilerplate code
Comprises the androidx.* packages

12. Android Jetpack | Overview
Simplify complex tasks
A collection of Android software components
Follow best practices
Free you from writing boilerplate code
Comprises the androidx.* packages

13. Android Jetpack | Overview
Simplify complex tasks
A collection of Android software components
Follow best practices
Free you from writing boilerplate code
Comprises the androidx.* packages

14. Android Jetpack | Components
Architecture
Foundation Behaviour
UI
•

15. Jetpack Components | Foundation
AppCompat
Android KTX
Multidex
Test
Architecture
Foundation Behaviour
UI
•
NEW

16. Jetpack Components | Architecture
DataBinding
Lifecycles
LiveData
Navigation
Paging
Room
ViewModel
WorkManager
Architecture
Foundation Behaviour
UI
•
NEW
NEW
NEW

17. Jetpack Components | UI
Animation & transitions
Auto
Emoji
Fragment
Layout
Palette
TV
Wear OS by Google
Architecture
Foundation Behaviour
UI
•

18. Jetpack Components | Behavior
Download manager
Media & playback
Notifications
Permissions
Sharing
Slices
Architecture
Foundation Behaviour
UI
•
NEW

19. androidx

20. androidx | Overview
com.android.support:support-fragment
com.android.support:cardview-v7
com.android.support:recyclerview-v7

21. androidx | Overview
com.android.support:fragment:support-fragment
com.android.support:cardview:cardview
com.android.support:recyclerview:recyclerview
androidx
androidx
androidx

22. androidx | Migrating to androidx
Manually
Automagically
Add both androidX=true and enableJetfier=true to
gradle.properties file
In Android Studio 3.2.1+: Refactor -> Migrate to AndroidX…

23. android-ktx

24. ANDROIDX.CORE:CORE-KTX

25. KOTLIN
sharedPreferences.edit()
.putBoolean("key", value)
.apply()

26. KOTLIN + ANDROID KTX
sharedPreferences.edit {
putBoolean("key", value)
}

27. KOTLIN
view.viewTreeObserver.addOnPreDrawListener(
object : ViewTreeObserver.OnPreDrawListener {
override fun onPreDraw(): Boolean {
viewTreeObserver.removeOnPreDrawListener(this)
actionToBeTriggered()
return true
}
}
)

28. KOTLIN + ANDROID KTX
view.doOnPreDraw {
actionToBeTriggered()
}

29. Architecture Components

30. Architecture Components | The Big Picture
Activity/Fragment
LiveData
LiveData
Repository
ViewModel
Local Data Source
Room
Remote Data Source
Retrofit
SQLite API

31. Architecture Components
Recipes™

32. Recipe #1 | ViewModel + Rx
Activity/Fragment
Repository
ViewModel
Local Data Source
Room
Remote Data Source
Retrofit
SQLite API
Single<T>
Single<T>
Single<T>
Subject<T>

33. Recipe #1 | ViewModel + Rx
class TrendingViewModel @Inject constructor(...) : BaseViewModel() {
private val uiStateSubject by lazy { BehaviorSubject<UiState>.create() }
fun loadTrending() {
uiStateSubject.onNext(UiState.Loading)
repository.loadTrending()
.doOnSuccess { trending -> uiStateSubject.onNext(UiState.Loaded(trending)) }
.doOnError { error -> uiStateSubject.onNext(UiState.Error(error)) }
.safeSubscribe()
}
fun observeUiState() : Observable<UiState> = uiStateSubject
}

34. Recipe #1 | ViewModel + Rx
class TrendingFragment: BaseDaggerFragment() {
fun loadTrending() {
viewModel.observeUiState()
.subscribe(::onUiStateChanged, ::onTrendingError)
fun onUiStateChanged(uiState: UiState){
when(uiState){
is UiState.Loading -> showLoading()
is UiState.Loaded -> showTrending(uiState.trending)
is UiState.Error -> hideLoading()
}
}
}

35. Recipe #2 | ViewModel + Rx + LiveData
Activity/Fragment
Repository
ViewModel
Local Data Source
Room
Remote Data Source
Retrofit
SQLite API
Single<T>
Single<T>
Single<T>
LiveData
LiveData

36. Recipe #2 | ViewModel + Rx + LiveData
class TrendingViewModel @Inject constructor(...) : BaseViewModel() {
private val _uiStateEvent = MutableLiveData<UiState>()
val uiStateEvent: LiveData<UiState>
get() = _uiStateEvent
fun loadTrending() {
repository.loadTrending()
.doOnSubscribe { _uiStateEvent.postValue(UiState.Loading) }
.doOnSuccess { _uiStateEvent.postValue(UiState.Loaded(trending)) }
.doOnError { _uiStateEvent.postValue(UiState.Error) }
.safeSubscribe()
}
}

37. Recipe #2 | ViewModel + LiveData (SingleLiveEvent)
Activity/Fragment
Repository
ViewModel
Local Data Source
Room
Remote Data Source
Retrofit
SQLite API
LiveData
LiveData
LiveData
LiveData
LiveData

38. Recipe #2 | ViewModel + LiveData (SingleLiveEvent)
class TrendingViewModel @Inject constructor(...) : BaseViewModel() {
private val _uiStateEvent = SingleLiveEvent<UiState>()
val uiStateEvent: LiveData<UiState>
get() = _uiStateEvent
fun loadTrending() {
_uiStateEvent.postValue(UiState.Loading)
val result = Transformations.map(repository.loadTrending()){
_uiStateEvent.postValue(UiState.Loaded(result.value))
}
}
}

39. Demo Time - Part 1

40. What players have adopted
Android Jetpack?

41. Android Jetpack adoption | top apps

42. What about Coroutines?

43. Before Coroutines | Ways to do async on Android
AsyncTasks
Loaders
Executors
ThreadPools
Rx

44. All of them relies onThreads

45. Coroutines | Brief history
Founded on Continuation principle
Concept first coined in 1958 by Melvin Conway
Like threads, but far away more lightweight
Tasks that can be suspended and resumed
Stable as of Kotlin 1.3
https://github.com/Kotlin/kotlinx.coroutines

46. Coroutines | Brief history
Founded on Continuation principle
Concept first coined in 1958 by Melvin Conway
Like threads, but far away more lightweight
Tasks that can be suspended and resumed
Stable as of Kotlin 1.3
https://github.com/Kotlin/kotlinx.coroutines

47. Coroutines | Brief history
Founded on Continuation principle
Concept first coined in 1958 by Melvin Conway
Like threads, but far away more lightweight
Tasks that can be suspended and resumed
Stable as of Kotlin 1.3
https://github.com/Kotlin/kotlinx.coroutines

48. Coroutines | Brief history
Founded on Continuation principle
Concept first coined in 1958 by Melvin Conway
Like threads, but far away more lightweight
Tasks that can be suspended and resumed
Stable as of Kotlin 1.3
https://github.com/Kotlin/kotlinx.coroutines

49. Coroutines | Brief history
Founded on Continuation principle
Concept first coined in 1958 by Melvin Conway
Like threads, but far away more lightweight
Tasks that can be suspended and resumed
Stable as of Kotlin 1.3
https://github.com/Kotlin/kotlinx.coroutines

50. Coroutines | Motivation
object: LoadingTask : AsyncTask() {
override fun doInBackground() {…}
override fun onPostExecute() {…}
}

51. Coroutines | Motivation
repository.loadTrending()
.flatMap {...}
.doOnEach {...}
.doOnError {...}
.subscribe(
onNext = { ... },
onError = { ... }
)
}
object: LoadingTask : AsyncTask() {
override fun doInBackground() {…}
override fun onPostExecute() {…}
}

52. Coroutines | Motivation
repository.loadTrending()
.flatMap {...}
.doOnEach {...}
.doOnError {...}
.subscribe(
onNext = { ... },
onError = { ... }
)
}
object: LoadingTask : AsyncTask() {
override fun doInBackground() {…}
override fun onPostExecute() {…}
}

53. Coroutines | Motivation

54. Coroutines | Motivation
fun loadTrending() = launch {
_uiStateEvent.postValue(UiState.Loading)
val result = async { /* load trending */ }.await()
_trendingData.postValue(Result.success(result))
_uiStateEvent.postValue(UiState.Loaded)
}

55. dependencies {
implementation
“org.jetbrains.kotlinx:kotlinx-coroutines-core:<version>”
implementation
“org.jetbrains.kotlinx:kotlinx-coroutines-android:<version>”
implementation
“org.jetbrains.kotlinx:kotlinx-coroutines-rx2:<version>”
}
Coroutines | Adding dependencies

56. Coroutines | Building blocks
Coroutine builder
Coroutine context
suspend function
builders to launch a coroutine
coroutine dispatchers
mark a suspension point

57. Coroutine builder | launch - synchronous coroutine
fun loadTrending() = launch {
_uiStateEvent.postValue(UiState.Loading)
val result = async { repository.loadTrending() }.await()
_trendingData.postValue(Result.success(result))
_uiStateEvent.postValue(UiState.Loaded)
}

58. Coroutine builder | launch - synchronous coroutine
fun loadTrending() = launch {
_uiStateEvent.postValue(UiState.Loading)
val result = async { repository.loadTrending() }.await()
_trendingData.postValue(Result.success(result))
_uiStateEvent.postValue(UiState.Loaded)
} Job

59. Coroutine builder | async - Loading coroutines in parallel
fun loadTrending() = launch {
_uiStateEvent.postValue(UiState.Loading)
val local = async { /* load local trending */ }.await()
val remote = async { /* load remote trending */ }.await()
val result = local + remote
_trendingData.postValue(Result.success(result))
_uiStateEvent.postValue(UiState.Loaded)
}

60. Coroutine builder | async - Loading coroutines in parallel
fun loadTrending() = launch {
_uiStateEvent.postValue(UiState.Loading)
val local = async { /* load local trending */ }.await()
val remote = async { /* load remote trending */ }.await()
val result = local + remote
_trendingData.postValue(Result.success(result))
_uiStateEvent.postValue(UiState.Loaded)
}
Deferred<T>
Deferred<T>

61. Coroutine context | Dispatchers
Main
IO
Default
Unconfined
UI Contexts
I/O operations
Uses heavy CPU
computation
No need to run on specific
context

62. Coroutine builder | withContext - Switching contexts
val uiContext: CoroutineContext = Dispatchers.Main
val ioContext: CoroutineContext = Dispatchers.IO
fun loadTrending() = launch(uiContext) {
_uiStateEvent.postValue(UiState.Loading)
val result = withContext(ioContext){ repository.loadTrending() }
_trendingData.postValue(Result.success(result))
_uiStateEvent.postValue(UiState.Loaded)
}

63. Coroutine builder | withContext - Switching contexts
val uiContext: CoroutineContext = Dispatchers.Main
val ioContext: CoroutineContext = Dispatchers.IO
fun loadTrending() = launch(uiContext) {
_uiStateEvent.postValue(UiState.Loading)
val result = withContext(ioContext){ repository.loadTrending() }
_trendingData.postValue(Result.success(result))
_uiStateEvent.postValue(UiState.Loaded)
}
parent coroutine

64. Coroutine builder | withContext - Switching contexts
val uiContext: CoroutineContext = Dispatchers.Main
val ioContext: CoroutineContext = Dispatchers.IO
fun loadTrending() = launch(uiContext) {
_uiStateEvent.postValue(UiState.Loading)
val result = withContext(ioContext){ repository.loadTrending() }
_trendingData.postValue(Result.success(result))
_uiStateEvent.postValue(UiState.Loaded)
}
Child coroutine
parent coroutine

65. Coroutine builder | withContext - Switching contexts
val uiContext: CoroutineContext = Dispatchers.Main
val ioContext: CoroutineContext = Dispatchers.IO
fun loadTrending() = launch(uiContext) {
_uiStateEvent.postValue(UiState.Loading)
val result = withContext(ioContext){ repository.loadTrending() }
_trendingData.postValue(Result.success(result))
_uiStateEvent.postValue(UiState.Loaded)
}
Child coroutine
parent coroutine

66. Coroutine builder | withContext - Switching contexts
val uiContext: CoroutineContext = Dispatchers.Main
val ioContext: CoroutineContext = Dispatchers.IO
fun loadTrending() = launch(uiContext) {
_uiStateEvent.postValue(UiState.Loading)
val result = withContext(ioContext){ repository.loadTrending() }
_trendingData.postValue(Result.success(result))
_uiStateEvent.postValue(UiState.Loaded)
}
Child coroutine
parent coroutine

67. Coroutines | suspending a point of execution
suspend fun loadTrending(){…}
⚠
Suspended coroutines must be called only from other
suspended ones.

68. Coroutines | suspend - suspending all the things!
suspend fun loadTrending() = trendingApi.loadTrending()
RemoteTrendingDataSource.kt
suspend fun loadTrending() = trendingDao.loadTrending()
LocalTrendingDataSource.kt
suspend fun loadTrending() =
localDataSource.loadTrending().await() +
remoteDataSource.loadTrending().await()
TrendingRepository.kt
fun loadTrending() = launch(uiContext) {
val result = async { repository.loadTrending() }
}
TrendingViewModel.kt

69. Taking off with Android
Jetpack + Coroutines

70. Recipe #2 | ViewModel + LiveData + Coroutines
Activity/Fragment
Repository
ViewModel
Local Data Source
Room
Remote Data Source
Retrofit
SQLite API
LiveData
LiveData
Deferred
Deferred Deferred
launch

71. Adding Coroutines | TrendingApi
interface TrendingApi {
@GET("/v1/gifs/trending")
fun loadTrending(): Deferred<TrendingResponse>
}

72. Adding Coroutines | ScopedViewModel + Coroutines
open class ScopedViewModel : ViewModel(), CoroutineScope {
override val coroutineContext = Main
protected val jobs = mutableListOf<Job>()
infix fun MutableList<Job>.add(job: Job) { this.add(job) }
override fun onCleared() {
super.onCleared()
jobs.forEach { if(!it.isCancelled) it.cancel() }
}
}

73. Adding Coroutines | TrendingViewModel
class TrendingViewModel : ScopedViewModel() {
fun loadTrending() {
jobs add launch {
_uiStateEvent.value = UiState.Loading
try {
val result = repository.loadTrending().await()
_uiStateEvent.value = UiState.Loaded(result)
} catch(t: Throwable) {
_uiStateEvent.value = UiState.Error
}
}
}
}

74. Living Code Time - Part 2

75. Q: Can Coroutines fully
replace Rx-ish code?

76. …

77. ramonrabello/Kiphy
AndroidX
Architecture Components
Material Theming
Coroutines
Dagger 2
Moshi
Kotlin 1.3

78. What’s next?

79. What’s next? | Android Jetpack
Modern Android development: Android Jetpack, Kotlin, and more
(Google I/O 2018)
https://www.youtube.com/watch?v=IrMw7MEgADk
Android X | Android Developers
https://developer.android.com/jetpack/androidx/
Android Jetpack | Android Developers
https://developer.android.com/jetpack/
Android KTX | Android Developers
https://developer.android.com/kotlin/ktx

80. What’s next? | Kotlin Coroutines
Utilizando Kotlin Coroutines no Android | Android Dev BR Medium
https://medium.com/android-dev-br/utilizando-kotlin-coroutines-no-android-
c73fcda71e27
Android Coroutine Recipes
https://developer.android.com/jetpack/androidx/
kotlinx.coroutines GitHub
https://www.github.com/Kotlin/kotlinx.coroutines
Android Suspenders | KotlinConf 2018
https://chris.banes.dev/talks/2018/android-suspenders/

81. Q & A

82. THANK YOU.
https://about.me/ramonrabello