Berlindroid: RxJava & Coroutines: A Practical Analysis

Kotlin has taken the Android world by storm, and is quickly becoming the most popular language, with coroutines approaching stability, does it make sense to replace your RxJava implementations for Coroutines?

Despite the hype, it may not make sense to jump on the bandwagon just yet, with RxJava having already proven its stability and usefulness, and in many cases the comparison between the two frameworks showing that they simply fit different purposes.

In this talk, you can learn how you can utilise the strengths of each framework, how to correctly choose the best solution for the requirements of your project, whether it may be beneficial to migrate or run them concurrently, and how you can start doing so for your project.

Transcript

1. RxJava & Coroutines A Practical Analysis @askashdavies
2. @askashdavies
3. @askashdavies
4. ! @askashdavies
5. Adoption @askashdavies
6. 7.7% (2015) @askashdavies
7. 19.5% (2016) 7.7% (2015) @askashdavies
8. 46.8% (2017) 19.5% (2016) 7.7% (2015) @askashdavies
9. blog.jetbrains.com/kotlin/2016/02/kotlin-1-0-released-pragmatic-language-for-jvm-and-android/
10. Multi Platform @askashdavies
11. Coroutines @askashdavies
12. fun main() { GlobalScope.launch { delay(1000L) println("World!") } println("Hello,") Thread.sleep(2000L) } @askashdavies
13. fun main() { GlobalScope.launch { delay(1000L) println("World!") } println("Hello,") Thread.sleep(2000L) } @askashdavies
14. fun main() { GlobalScope.launch { delay(1000L) println("World!") } println("Hello,") Thread.sleep(2000L) } @askashdavies
15. ⚖ Stability @askashdavies
16. @askashdavies
17. async / launch @askashdavies
18. val deferred: Deferred<String> = async { "Hello" } @askashdavies
19. val result: String = deferred.await() @askashdavies
20. val job: Job = launch { "Hello" } @askashdavies
21. job.join() @askashdavies
22. @Annotations bit.ly/2BrxgKv @askashdavies
23. ! Here be dragons @askashdavies
24. ⚠ @ExperimentalCoroutinesApi @askashdavies
25. ⚠ @ObsoleteCoroutinesApi @askashdavies
26. ☠ @InternalCoroutinesApi @askashdavies
27. @askashdavies
28. @askashdavies
29. Coroutines ! Best thing since sliced bread @askashdavies
30. Coroutines Best thing since ... brotchen? @askashdavies
31. ! Coroutines @askashdavies
32. ! Native first-party library @askashdavies
33. ! Easy-to-use @askashdavies
34. ! suspend fun @askashdavies
35. Dispatchers.Main @askashdavies
36. ! History of Android @askashdavies
37. Background Processes @askashdavies
38. Background Processes ! Runnable / Handler @askashdavies
39. Background Processes ! AsyncTask @askashdavies
40. Background Processes ! IntentService @askashdavies
41. Background Processes ! Loader<T> @askashdavies
42. Background Processes WorkManager @askashdavies
43. Background Processes AlarmManager @askashdavies
44. Background Processes AlarmManager, CountDownTimer @askashdavies
45. Background Processes AlarmManager, CountDownTimer , FutureTask<T> @askashdavies
46. Background Processes AlarmManager, CountDownTimer , FutureTask<T>, GcmNetworkManager @askashdavies
47. Background Processes AlarmManager, CountDownTimer , FutureTask<T>, GcmNetworkManager, HandlerThread @askashdavies
48. Background Processes AlarmManager, CountDownTimer , FutureTask<T>, GcmNetworkManager, HandlerThread, JobDispatcher @askashdavies
49. Background Processes AlarmManager, CountDownTimer , FutureTask<T>, GcmNetworkManager, HandlerThread, JobDispatcher, JobScheduler @askashdavies
50. Background Processes AlarmManager, CountDownTimer , FutureTask<T>, GcmNetworkManager, HandlerThread, JobDispatcher, JobScheduler, ScheduledThreadPoolExecutor @askashdavies
51. Background Processes AlarmManager, CountDownTimer , FutureTask<T>, GcmNetworkManager, HandlerThread, JobDispatcher, JobScheduler, ScheduledThreadPoolExecutor, Timer @askashdavies
52. Background Processes AlarmManager, CountDownTimer , FutureTask<T>, GcmNetworkManager, HandlerThread, JobDispatcher, JobScheduler, ScheduledThreadPoolExecutor, Timer, Task<T> @askashdavies
53. ! @askashdavies
54. xkcd.com/927/
55. RxJava to the rescue @askashdavies
56. ⛓ Chained operations @askashdavies
57. ⬆ ⬇ Abstracted threading @askashdavies
58. ! Reactive programming @askashdavies
59. ! @askashdavies
60. @askashdavies
61. @askashdavies
62. @askashdavies
63. @askashdavies
64. @askashdavies
65. @askashdavies
66. ! Asynchronous API's @askashdavies
67. ! Synchronous API's @askashdavies
68. Observable.fromIterable() @askashdavies
69. Flowable / Observable Single / Completable / Maybe @askashdavies
70. @askashdavies
71. ! Observable .fromIterable(resourceDraft.getResources()) .flatMap(resourceServiceApiClient::createUploadContainer) .zipWith(Observable.fromIterable(resourceDraft.getResources()), Pair::create) .flatMap(uploadResources()) .toList() .toObservable() .flatMapMaybe(resourceCache.getResourceCachedItem()) .defaultIfEmpty(Resource.getDefaultItem()) .flatMap(postResource(resourceId, resourceDraft.getText(), currentUser, resourceDraft.getIntent())) .observeOn(AndroidSchedulers.mainThread()) .subscribeOn(Schedulers.io()) .subscribe( resource -> repository.setResource(resourceId, resource, provisionalResourceId), resourceUploadError(resourceId, resourceDraft, provisionalResourceId) ); @askashdavies
72. @askashdavies
73. ⚙ Hidden complexity @askashdavies
74. ! Hidden gotchas @askashdavies
75. ! Memory footprint @askashdavies
76. ⤴ Steep learning curve @askashdavies
77. explosm.net/comics/3185/
78. @askashdavies
79. #RxMustDie pca.st/7IJG @askashdavies
80. "If all you have is a hammer, everything looks like a nail" — Abraham Maslow, The Psychology of Science, 1966 @askashdavies
81. Reactive / Imperative @askashdavies
82. Coroutine Use Cases @askashdavies
83. Network Call Handling // RxJava2 fun getUser(): Single<User> = Single.fromCallable { /* ... */ } // Coroutine suspend fun getUser(): User = /* ... */ @askashdavies
84. Cache Retrieval // RxJava2 fun getUser(): Maybe<User> = Maybe.fromCallable { /* ... */ } // Coroutine suspend fun getUser(): User? = /* ... */ @askashdavies
85. Background Task Handling // RxJava2 fun storeUser(user: User): Completable.fromCallable { /* ... */ } // Coroutine suspend fun storeUser(user: User) { /* ... */ } @askashdavies
86. RxJava2 / Coroutines Single<T> / T Maybe<T> / T? Completable / Unit @askashdavies
87. Thread Handling // RxJava2 getUser() .subscribeOn(Schedulers.computation()) .observeOn(AndroidSchedulers.mainThread()) .subscribe { /* Do something */ } // Coroutine launch(Dispatchers.Main) { val user = getUser() /* Do something */ } @askashdavies
88. ! FlatMap // RxJava2 getUser() .flatMap { doSomethingWithUser(it) } .subscribeOn(Schedulers.computation()) .observeOn(AndroidSchedulers.mainThread()) .subscribe { /* Do something else */ } // Coroutine launch(Dispatchers.Main) { val user = getUser() val smth = doSomethingWithUser(user) /* Do something else */ } @askashdavies
89. Callback Consumption // RxJava2 fun getSingle(): Single = Single.create<T> { emitter -> doSomethingAsync(object: Callback<T> { override fun onComplete(result: T) = emitter.onSuccess(result) override fun onException(exception: Exception) = emitter.onError(exception) }) } // Coroutine suspend fun getCoroutine() : T = suspendCoroutine { continuation -> doSomethingAsync(object : Callback<T> { override fun onComplete(result: T) = continuation.resume(result) override fun onException(exception: Exception) = continuation.resumeWithException(exception) }) } @askashdavies
90. ! Continuation @askashdavies
91. Task Cancellation // RxJava2 val disposable: Disposable = Single .create { /* Do something */ } .subscribe { /* Do something else */ } disposable.dispose() // Coroutine val parent: Job = Job() launch(Dispatchers.Main + parent) { /* Do something */ } parent.cancelChildren() @askashdavies
92. ViewModel.viewModelScope androidx.lifecycle:2.1.0-alpha01 bit.ly/2FZ0FPN @askashdavies
93. Lifecycle Task Cancellation class MainViewModel : ViewModel { fun init() { viewModelScope.launch { someSuspendFunction() } } } @askashdavies
94. Value Streams // RxJava2 val publisher = PublishSubject() publisher.subscribe { /* Do something */ } publisher.onNext("Hello") // Coroutine val channel = Channel<String>() launch { channel.send("Hello") } launch { channel.consumeEach { /* Do something */ } } @askashdavies
95. ! Backpressure @askashdavies
96. ! Backpressure launch { channel.send("Hello") } @askashdavies
97. ! RxJava @askashdavies
98. Channels bit.ly/2DQU7lb @askashdavies
99. ↔ Transformations @askashdavies
100. ❄ Cold Streams @askashdavies
101. ⚙ Complex Business Logic @askashdavies
102. Asynchronicity Comparison Manuel Vivo (@manuelvicnt) bit.ly/2R27stP @askashdavies
103. Is Coroutines a replacement for RxJava? @askashdavies
104. Maybe... @askashdavies
105. Should I migrate to Coroutines? @askashdavies
106. Probably not... @askashdavies
107. "Don't fix what ain't broke" — Some Guy @askashdavies
108. © 2019 Viacom International Inc.
109. Did you migrate to Coroutines? @askashdavies
110. ! Yes! @askashdavies
111. How could I migrate to Coroutines? @askashdavies
112. ! Migration Policy @askashdavies
113. Retrofit Services @askashdavies
114. Retrofit2 Coroutines Adapter bit.ly/2TyGXOh com.jakewharton.retrofit:retrofit2-kotlin-coroutines-adapter:+ @askashdavies
115. interface UserService { @GET("/user") fun getUser(): Deferred<User> } val retrofit = Retrofit.Builder() .baseUrl("https://example.com/") .addCallAdapterFactory(CoroutineCallAdapterFactory()) .build() GlobalScope.launch { val user = retrofit .create<UserService>() // >= 2.5.0 .getUser() .await() } @askashdavies
116. interface UserService { @GET("/user") fun getUser(): Deferred<User> } val retrofit = Retrofit.Builder() .baseUrl("https://example.com/") .addCallAdapterFactory(CoroutineCallAdapterFactory()) .build() GlobalScope.launch { val user = retrofit .create<UserService>() // >= 2.5.0 .getUser() .await() } @askashdavies
117. interface UserService { @GET("/user") fun getUser(): Deferred<User> } val retrofit = Retrofit.Builder() .baseUrl("https://example.com/") .addCallAdapterFactory(CoroutineCallAdapterFactory()) .build() GlobalScope.launch { val user = retrofit .create<UserService>() // >= 2.5.0 .getUser() .await() } @askashdavies
118. interface UserService { @GET("/user") fun getUser(): Deferred<User> } val retrofit = Retrofit.Builder() .baseUrl("https://example.com/") .addCallAdapterFactory(CoroutineCallAdapterFactory()) .build() GlobalScope.launch { val user = retrofit .create<UserService>() // >= 2.5.0 .getUser() .await() } @askashdavies
119. Retrofit bit.ly/2CU0LUK First-party "suspend" support @askashdavies
120. Coroutines RxJava2 bit.ly/2DQ2ZYn org.jetbrains.kotlinx:kotlinx-coroutines-rx2:+ @askashdavies
121. Name Scope Description rxCompletable CoroutineScope Cold completable that starts coroutine on subscribe rxMaybe CoroutineScope Cold maybe that starts coroutine on subscribe rxSingle CoroutineScope Cold single that starts coroutine on subscribe rxObservable ProducerScope Cold observable that starts coroutine on subscribe rxFlowable ProducerScope Cold observable that starts coroutine on subscribe with backpressure support @askashdavies
122. val service: UserService = /* ... */ GlobalScope.rxSingle { service.getUser() } .observeOn(AndroidSchedulers.mainThread()) .subscribeOn(Schedulers.io()) .subscribe( { /* Do something with user */ }, { /* Handle error ... maybe */ } ) @askashdavies
123. Completable.await() GlobalScope.launch { Completable .complete() .await() } @askashdavies
124. Maybe.await() GlobalScope.launch { val result: String? = Maybe .fromCallable { null as String? } .await() } @askashdavies
125. Observable.await... bit.ly/2Tl37TK GlobalScope.launch { val observable = Observable.just(1, 2, 3, 4) // Await first item val item = observable.awaitFirst() // Print each item observable.consumeEach { println(it) } // Consume all items observable .openSubscription() .consume { println(it.size) } } @askashdavies
126. ! Conclusion @askashdavies
127. @askashdavies
128. Cheers! ! @askashdavies
129. @askashdavies