Programação assíncrona utilizando Coroutines

O desenvolvimento de aplicações Android comumente exigem a criação de chamadas assíncronas, que podem acabar gerando diversos problemas como por exemplo o famigerado callback hell. As Coroutines oferecem uma maneira de escrever códigos assíncronos de forma sequencial em uma co-rotina, possibilitando um código mais compacto, fácil de gerenciar e alterar, além de gerar as chamadas lightweight threads, muito mais performáticas que as threads comuns. Nessa palestra vamos mostrar as principais features do Coroutines que podem resolver esse tipo de problema.

Transcript

1. Programação assíncrona utilizando Coroutines
2. Diego Gonçalves Santos Desenvolvedor @
3. Coroutines
4. Código Assíncrono
5. Cenário Imagine que você está usando a API do TDC e que para usar os serviços é necessário enviar sua chave e receber os tokens de autenticação.
6. Single Thread fun listEvents() { val token = getToken() val events = getEvents(token) displayEvents(events) }
7. Callbacks fun listEvents() { getTokenAsync { token -> getEventsAsync(token) { events -> displayEvents(events) } } }
8. Callbacks fun listEvents() { getTokenAsync { token -> getEventsAsync(token) { events -> displayEvents(events) } } } Callback Hell!!
9. RX R Exemplo de código usando Rx fun listEvents() { requestTokenAsync() .flatMap { token -> requestEventsAsync(token) } .subscribe({ events -> displayEvents(events)}) }
10. RX Curva de aprendizado íngreme
11. Coroutines suspend fun getTokenAsync() {...} suspend fun getEventsAsync() {...} suspend fun listEvents() { val token = getTokenAsync() val events = getEventsAsync(token) displayEvents(events) }
12. Coroutines Coroutines permitem que você escreva seu código de forma sequencial e cria light-weight threads para lidar com o código assíncrono.
13. Coroutines Coroutines precisam de um contexto especial para rodar, portanto elas só rodam dentro de Coroutine Builders ou dentro de outras Coroutines
14. Launch (sequencial)
15. Coroutines Builders Launch launch { delay(1000L) println("World!") } println("Hello,") Thread.sleep(2000L)
16. Coroutines Builders Launch launch { delay(1000L) println("World!") } println("Hello,") Thread.sleep(2000L) Hello, World!
17. Coroutines Builders Launch - Job Join val job = launch { delay(1000L) println("World!") } println("Hello,") job.join()
18. Coroutines Builders Launch - Job Join val job = launch { delay(1000L) println("World!") } println("Hello,") job.join() Fork Coroutine Main Thread Join
19. Coroutines Builders Launch - Job Join val job = launch { delay(1000L) println("World!") } println("Hello,") job.join() Hello, World!
20. Coroutines Builders Launch - Job Cancel val job = launch { repeat(1000) { i -> println("I'm sleeping $i ...") delay(500L) } } delay(1300L) // delay a bit println("main: I'm tired of waiting!") job.cancel() // cancels the job job.join() // waits for job's completion println("main: Now I can quit.")
21. Coroutines Builders Launch - Job Cancel val job = launch { repeat(1000) { i -> println("I'm sleeping $i ...") delay(500L) } } delay(1300L) // delay a bit println("main: I'm tired of waiting!") job.cancel() // cancels the job job.join() // waits for job's completion println("main: Now I can quit.") I'm sleeping 0 ... I'm sleeping 1 ... I'm sleeping 2 ... main: I'm tired of waiting! main: Now I can quit.
22. Coroutines Builders Launch - Job Cancel And Join val job = launch { repeat(1000) { i -> println("I'm sleeping $i ...") delay(500L) } } delay(1300L) // delay a bit println("main: I'm tired of waiting!") job.cancelAndJoin() println("main: Now I can quit.") I'm sleeping 0 ... I'm sleeping 1 ... I'm sleeping 2 ... main: I'm tired of waiting! main: Now I can quit.
23. Coroutines Builders Launch - Quando a Coroutine para de ser processada ? val job = launch { var i = 0 while (i <= 5000) { println("I'm sleeping ${i++} ...") } } delay(1300L) println("main: I'm tired of waiting!") job.cancelAndJoin() println("main: Now I can quit.") I'm sleeping 0 ... I'm sleeping 1 ... I'm sleeping 2 … … I'm sleeping 5000 … main: I'm tired of waiting! main: Now I can quit.
24. Coroutines Builders Launch - Garantindo que a Coroutine vai parar quando solicitado val job = launch { var i = 0 while (isActive) { if(i <= 5000) { println("I'm sleeping ${i++} ...")} } delay(1000) println("main: I'm tired of waiting!") job.cancelAndJoin() println("main: Now I can quit.") I'm sleeping 0 ... I'm sleeping 1 ... I'm sleeping 2 ... main: I'm tired of waiting! main: Now I can quit.
25. RunBlocking (Bloqueia Thread)
26. Coroutines Builders Run Blocking val job = runBlocking { delay(1000L) println("World!") } println("Hello,") job.join()
27. Coroutines Builders Run Blocking val job = runBlocking { delay(1000L) println("World!") } println("Hello,") job.join() World! Hello,
28. Coroutines Builders Launch - UI Context suspend fun listEvents() { launch(UI) { val token = getTokenAsync() val events = getEventsAsync(token) displayEvents(events) } }
29. Async (concorrente)
30. Coroutines Builders Launch - Sequencial launch{ val image1 = loadImage1() val image2 = loadImage2() setBackgrounds(image1, image2) }
31. Coroutines Builders Async - Concorrente val image1 = async { loadImage1() } val image2 = async { loadImage2() } setBackgrounds(image1.await(), image2.await())
32. Codifique sequencialmente sem receio! Use loops, high-order functions, etc for (i in 1..100_000) { launch { doSomethingHeavy() } }
33. Coroutines vs Threads
34. Cenário Sistema que recebe uma requisição, lê o arquivo local, faz o upload desse arquivo e retorna a url para acessar esse arquivo
35. Single Thread
36. Multiple Threads
37. Coroutines - Sub-rotinas
38. Coroutines - non-preemptive multi-tasking Usar os recursos de forma eficiente e multi-tarefas colaborativa onde as próprias funções controlam o fluxo, disponibilizam a thread e continuam depois de onde pararam, sem a intervenção de um SO.
39. Coroutines - SÃO light-weight threads val jobs = List(100_000) { launch { delay(1000L) print(".") } } jobs.forEach { it.join() }
40. Não existe mágica: De Callbacks para código sequencial
41. Direct Style vs Continuation-Passing Style
42. Direct Style fun listEvents() { val token = getToken() val events = getEvents(token) displayEvents(events) } Continuation
43. Continuation-Passing Style fun listEvents() { getTokenAsync { token -> getEventsAsync(token) { events -> displayEvents(events) } } } Continuation
44. Coroutines Direct Style suspend fun listEvents() { val token = getToken() val events = getEvents(token) displayEvents(events) } Continuation
45. Como é possível código assíncrono sem callbacks?
46. Convertendo para CPS suspend fun listEvents() {...}
47. Convertendo para CPS suspend fun listEvents() {...} Java/JVM callback Object listEvents(Continuation<Void> cont) {...}
48. Convertendo para CPS suspend fun listEvents() {...} Java/JVM callback Object listEvents(Continuation<Void> cont) {...} interface Continuation<in T> { val context: CoroutineContext fun resume(value: T) fun resumeWithException(exception: Throwable) }
49. Convertendo para CPS suspend fun listEvents() { val token = getToken() val events = getEvents(token) displayEvents(events) } Continuation Inicial
50. Convertendo para CPS suspend fun listEvents() { val token = getToken() val events = getEvents(token) displayEvents(events) } Continuation
51. Convertendo para CPS suspend fun listEvents() { val token = getToken() val events = getEvents(token) displayEvents(events) } Continuation
52. Callbacks? fun listEvents() { getTokenAsync { token -> getEventsAsync(token) { events -> displayEvents(events) } } }
53. Convertendo para CPS suspend fun listEvents() { // Label 0 val token = getToken() // Label 1 val events = getEvents(token) // Label 2 displayEvents(events) }
54. Convertendo para CPS suspend fun listEvents(Continuation<Void> cont) { val sm = object: CoroutineImpl {...} switch(sm.label) { case 0: getToken(sm) case 1: getEvents(sm.token, sm) case 2: displayEvents(sm.events) } }
55. Convertendo para CPS suspend fun listEvents(Continuation<Void> cont) { val sm = object: CoroutineImpl {...} switch(sm.label) { case 0: sm.label = 1 getToken(sm) case 1: ... } }
56. Convertendo para CPS suspend fun listEvents(Continuation<Void> cont) { val sm = object: CoroutineImpl { fun resume(...) { listEvents(this) } } switch(sm.label) { case 0: ... } }
57. Convertendo para CPS suspend fun listEvents(Continuation<Void> cont) { val sm = object: CoroutineImpl {...} switch(sm.label) { case 0: ... case 1: sm.label = 2 getEvents(sm.token, sm) } }
58. Extensions
59. Extension em Strings fun String.toNumber(): String { return NumberFormat.getInstance() .format(this.toDouble()) }
60. Extension em Strings fun String.toNumber(): String { return NumberFormat.getInstance() .format(this.toDouble()) } val numberString = “1” val number = numberString.toNumber()
61. Adaptando callbacks para Coroutines
62. Chamada convencional Retrofit requestToken(). enqueue(object : Callback<T> { override fun onResponse(call: Call<T>?, response: Response<T>) { // Handle response } override fun onFailure(call: Call<T>, t: Throwable) { // Handle error } })
63. Chamada convertida para Coroutine suspend fun <T : Any?> Call<T>.awaitResponse(): Response<T> { return suspendCancellableCoroutine { continuation -> enqueue(object : Callback<T> { override fun onResponse(call: Call<T>?, response: Response<T>) { if (response.isSuccessful) continuation.resume(response) else continuation.resumeWithException(Throwable()) } override fun onFailure(call: Call<T>, t: Throwable) { if (continuation.isCancelled) return continuation.resumeWithException(t) } }) } }
64. Chamada convertida para Coroutine suspend fun <T : Any?> Call<T>.awaitResponse(): Response<T> { ... } val token = requestToken().awaitResponse()
65. Testando Coroutines
66. Testando Coroutines • Organizar as camadas da sua aplicação • Mantenha o Coroutine Builder na view • Use runBloking no teste • You are free to go!
67. Testando Coroutines
68. Testando Coroutines
69. Projeto de Exemplo https://github.com/DiegoGSantos/Coroutines-Example
70. Libs interessantes usando Coroutines • Kotlin Coroutines for Retrofit https://github.com/gildor/kotlin-coroutines-retrofit • Kotlin Coroutine (Experimental) Adapter https://github.com/JakeWharton/retrofit2-kotlin-coroutines-adapter • Peko https://github.com/deva666/Peko • Anko Coroutines https://github.com/Kotlin/anko/wiki/Anko-Coroutines • Prefekt https://github.com/StylingAndroid/Prefekt
71. Referências KotlinConf 2017 - Introduction to Coroutines by Roman Elizarov https://www.youtube.com/watch?v=_hfBv0a09Jc&t=34s KotlinConf 2017 Deep Dive into Coroutines on JVM by Roman Elizarov https://www.youtube.com/watch?v=YrrUCSi72E8 Github official: https://github.com/Kotlin/kotlinx.coroutines Android + kotlin coroutines: Async de um jeito "diferente", por Walmyr Carvalho (Android Meetup #55) https://www.youtube.com/watch?v=Yr2p4gLUwBA
72. Referências Artigos http://blog.alexnesterov.com/post/coroutines/ https://superkotlin.com/coroutines/ https://en.wikipedia.org/wiki/Cooperative_multitasking https://android.jlelse.eu/a-first-walk-into-kotlin-coroutines-on-android-fe4a6e25f46a Artigos sobre essa palestra no blog da Dextra http://dextra.com.br/pt/android/introducao-as-coroutines/ http://dextra.com.br/pt/android/coroutines-nos-bastidores/
73. Obrigado! Diego Gonçalves Santos DiegoGSantos DiegoGSantos @DiegoGSantos DiegoGSantos