Kotlin Coroutines ことはじめ

by M.Inomata

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Kotlin Coroutines ͜ͱ͸͡Ί

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ࣗݾ঺հ • w ழມॆԝ ͍ͷ·ͨΈͭͻΖ w ᷂UFDIWFJO୅දɻ  J04"OESPJEεϚϗΞϓϦΤϯδχΞɻ  3Y͕޷͖Ͱ͢ɻ w QSJWBUFUXJUUFS!JOP

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ࠓ೔ͷ࿩ • Kotlinίϧʔνϯͷجຊͱ࢓૊ΈΛ஌Ζ͏

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ҰൠతʹɺCoroutine ͱ͸ • தஅɾ࠶։͕Մೳͳαϒϧʔνϯ • ฒߦੑ(Concurrent)Λఏڙ͢Δ

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αϒϧʔνϯʹී௨ͷؔ਺(ͳͲ) αϒϧʔνϯ ؔ਺ͳͲ ॲཧ ॲཧ ॲཧ ʜ SFUVSOl)FMMP 8PSMEl ϝΠϯॲཧ αϒϧʔνϯ։࢝ ʜ αϒϧʔνϯऴྃ

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ίϧʔνϯʹதஅՄೳͳαϒϧʔνϯ ίϧʔνϯ ॲཧ ZJFMElIFMMPz ॲཧ ZJFMElXPSMEz ॲཧ ʜ ϝΠϯॲཧ ίϧʔνϯ։࢝ ʜ ίϧʔνϯऴྃ

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ίϧʔνϯ͸ ฒߦ(Concurrent)ʹಈ࡞͢Δ εϨου" ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ εϨου# ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ

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ฒߦ(Concurrent) ͱ ฒྻ(Parallel) • ฒߦ(Concurrent) ͷྫ: Coroutine • ฒྻ(Parallel) ͷྫ: ϚϧνεϨουɾϚϧνϓ ϩηε

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ฒߦ(Concurrent) != ฒྻ(Parallel) εϨου" ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ͜Ε͸ฒߦͰ͋ͬͯ  ฒྻͰ͸ͳ͍ ͜Ε͸ฒߦͰ΋  ฒྻͰ΋͋Δ εϨου# εϨου" ίϧʔνϯ ίϧʔνϯ

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Coroutines   are   light-weight.

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Kotlin Coroutines

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Kotlin Coroutine ͷΩϞ • Suspending Function • Structured concurrency • CoroutineContext • Async as Sync

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Kotlin CoroutineͷΩϞᶃ  Suspending Function

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Suspending Function • Kotlin Coroutines ͸ɺίϧʔνϯͷதஅͰ͖ Δੑ࣭Λ suspend ؔ਺(Suspending Function)Ͱ࣮ݱ͍ͯ͠Δɻ

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Suspending Function ͷੑ࣭ • suspend ؔ਺͸ଞͷ suspend ؔ਺ͷதͰ͔͠ ࣮ߦͰ͖ͳ͍ɻ • ࢠͷ suspend ؔ਺͕தஅ͢Δͱɺ਌ͷ suspend ؔ਺΋ࢭ·Δɻ • suspend ؔ਺ͷதͰී௨ͷؔ਺(suspendͰͳ ͍ؔ਺)ΛݺͿ͜ͱ͸Ͱ͖Δɻ

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Hello world to Kotlin Coroutine

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͜ͷαϯϓϧͰ࢖͍ͬͯΔؔ਺ • ίϧʔνϯϏϧμʔ(ੜ੒ؔ਺): • runBlocking { ... } • CoroutineScope#launch { ... } • suspendؔ਺:  delay(timeMillis: Long) ※஫: runBlocking͸ཚ༻NGɻ  ɹɹAndroid؀ڥͰ͸࢖Θͳ͍͜ͱʂ

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Android ൛

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CoroutineScopeΫϥε • ίϧʔνϯͷੜଘظؒΛ؅ཧ͢ΔΦϒδΣΫτɻ • MainScope ... UIεϨουͰಈ࡞͢Δείʔϓɻ   → AndroidͷActivity ͳͲͱඥ෇͚ͯը໘ͷ  ɹϥΠϑαΠΫϧͱҰகͤ͞ΒΕΔɻ • GlobalScope ... ΞϓϦͷੜଘظؒͱಉ͡είʔϓɻ  → όονॲཧͳͲɺΞϓϦੜଘதʹऴΘͬͯ͸ࠔΔॲཧΛ࣮ߦ͢Δɻ

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αεϖϯυؔ਺ͷྫ • delay (timeMillis: Long)   ... ࢦఆϛϦඵ଴ͭɻ • withTimeout(timeMillis: Long) { ... } withTimeoutOrNull(timeMillis: Long) { ...}  ... ϒϩοΫ಺ͷॲཧ͕ࢦఆϛϦඵΛ௒͑ͨͱ͖ʹ  ɹλΠϜΞ΢τͤ͞Δɻ • yield()   ... ॲཧΛॠஅͯ͠ɺ(͋Ε͹)ଞͷίϧʔνϯʹॲཧΛճ͢ɻ

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suspend ͸ϊϯϒϩοΩϯά • suspend = தஅ • ͚ͩͲɺεϨουΛϒϩοΫ͠ͳ͍ • →εϨουΛϒϩοΫ͢Δྫ: Thread.sleep()

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Coroutine ͷ suspend ؔ਺͸ॲཧΛதஅͯ͠ɺ ଞͷฒߦॲཧதͷίϧʔνϯʹεϨουΛৡΔɻ εϨου" ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ZJFME

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εϨου" ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ZJFME

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εϨου" ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ZJFME ZJFME ZJFME

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Suspend Function Ͱ ίϧʔνϯͷதஅͰ͖Δੑ࣭Λ ࣮ݱ͍ͯ͠Δ

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Kotlin CoroutineͷΩϞᶄ  Structured Concurrency

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Structured concurrency ฒߦੑͷߏ଄Խ • ίϧʔνϯ͸਌ࢠؔ܎Λ࣋ͯΔɻ ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ

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Α͋͘ΔϚϧνεϨουͳ  ඇಉظॲཧͷ໰୊ • Ұ෦ͷεϨουΛམͱͨ͠(མͪͨ)ͱ͖ʹɺ  ࢒ΓͷεϨουΛڠௐͤ͞Δͷ͕େมɻ • λΠϛϯά໰୊ͰσουϩοΫͨ͠Γɺҙਤ͠ͳ ͍ڍಈ͕ى͜Γ΍͍͢ɻ • ໰୊͕ى͖ͨͱ͖ʹݪҼڀ໌ɾσόοά͕೉͠ ͍ɻ

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਌ࢠؔ܎ͷ͋Δίϧʔνϯ͸  ڠௐͤ͞΍͍͢

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਌ࢠؔ܎ͷ͋Δίϧʔνϯ͸  ڠௐͤ͞΍͍͢ ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ΞΫςΟϒͳ ίϧʔνϯ

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਌͸ࢠڙͷऴྃΛ଴ͬͯऴྃ͢Δ ΞΫςΟϒͳ ίϧʔνϯ ଴ػதͷ ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ

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਌ࢠؔ܎ͷ͋Δίϧʔνϯ͸  ྫ֎ɾΩϟϯηϧ࣌΋ڠௐͤ͞΍͍͢

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਌ࢠؔ܎ͷ͋Δίϧʔνϯ͸  ྫ֎ɾΩϟϯηϧ࣌΋ڠௐͤ͞΍͍͢ ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ྫ֎ൃੜʂ

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਌ίϧʔνϯʹྫ֎Λ఻೻ͯ͠  ίϧʔνϯΛऴྃ͢Δ ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ྫ֎ൃੜʂ ྫ֎εϩʔ ྫ֎εϩʔ

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਌ίϧʔνϯ͕ऴྃ͢Δ࣌͸ɺ  ࢠίϧʔνϯ΋Ωϟϯηϧ͢Δ ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ ྫ֎ൃੜʂ KPCDBODFM KPCDBODFM

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ʹ਌ίϧʔνϯΛࢭΊΕ͹ɺ ࢠίϧʔνϯ΋ࢭ·Δ

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਌ࢠϧʔνϯͷείʔϓΛ Ωϟϯηϧ͢Ε͹ɺ ਌ࢠͱ΋Ͳ΋ࢭΊΒΕΔ

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ίϧʔνϯͷ࣮ߦείʔϓΛ  Ωϟϯηϧ͢Δ͚ͩͰશ෦ࢭΊΒΕΔ ίϧʔνϯ .BJO4DPQF KPCDBODFM "DUJWJUZ PO%FTUSPZ TDPQFDBODFM ίϧʔνϯ KPCDBODFM

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(࠶ܝ) Android Hello world

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ίϧʔνϯ͸Ͳ͏΍ͬͯ ਌ࢠؔ܎Λ࡞͍ͬͯΔͷ͔ʁ → CoroutineScope

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launch ͷϥϜμࣜ͸  this = CoroutineScope

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ίϧʔνϯ .BJO4DPQF KPCDBODFM "DUJWJUZ PO%FTUSPZ TDPQFDBODFM ίϧʔνϯ ίϧʔνϯ KPCDBODFM (MPCBM4DPQF GlobalScopeͷίϧʔνϯ͸.BJO4DPQFͱؔ܎ͳ͘ಈ͘ʂ launch launch launch

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Structured Concurrency Λ ׆༻͢Ε͹ ίϧʔνϯ؅ཧָ͕ʹͳΔ

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Kotlin CoroutineͷΩϞᶅ  CoroutineContext

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CoroutineContext %JTQBUDIFSɿ.BJO +PCɿͳ͠ ϝΠϯείʔϓͷίϯςΩετ %JTQBUDIFSɿ.BJO +PCɿίϧʔνϯ είʔϓ1ͷίϯςΩετ %JTQBUDIFSɿ.BJO +PCɿίϧʔνϯ είʔϓͷίϯςΩετ %JTQBUDIFSɿ%FGBVMU +PCɿίϧʔνϯ είʔϓͷίϯςΩετ ϝΠϯείʔϓ ίϧʔνϯ ίϧʔνϯ ίϧʔνϯ1ͷείʔϓ είʔϓ ίϧʔνϯͷείʔϓ είʔϓ ίϧʔνϯ ίϧʔνϯͷείʔϓ είʔϓ

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CoroutineContextͷྫ: Job  ͋Δίϧʔνϯͷ࣮ߦΛද͢Πϯελϯε • ίϧʔνϯΛ࣮ߦ͢ΔͱJobΛ͔͑͢ɻ

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CoroutineContextͷྫ: CorouttineDispatcher  ίϧʔνϯΛͲͷεϨουͰಈ͔͔͢ΛܾΊΔਓ • Dispatches.Main • Dispatchers.Default • Dispatchers.IO • Dispatchers.Unconﬁned • ͦͷଞ: newSingleThreadContext("threadName") ͳͲ

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CoroutinenContextͷྫ:ͦͷଞ • CoroutineName("name") • NonCancellable • CoroutineExceptionHandler {}

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CoroutineContextͷ࢖͍ํ • ίϧʔνϯϏϧμʔͷҾ਺ʹࢦఆͯ͠࢖͏ • + Ͱ࿈݁ʢॏෳͨ͠ઃఆ͸ӈล༏ઌʣͯ͠૊Έ߹ Θͤͯ࡞Δ

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CoroutineContextͷ࢖͍ํ • ಉظతʹৼΔ෣ͬͯ͘ΕΔ withContext ͕ศར

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Kotlin CoroutineͷΩϞᶅ  Async as Sync

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TwitterΫϥΠΞϯτతͳ ΞϓϦ࣮૷ΛίϧʔνϯͰߟ͑Δɻ ϩάΠϯ 0, λΠϜϥΠϯऔಘ < l͓͸Α͏z lࠓ೔͸ษڧձͰ͢z >

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ίϧʔνϯ͸ඇಉظ • ྫ: ϩάΠϯͯ͠λΠϜϥΠϯऔಘ͢ΔAPI࣮૷

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ίϧʔνϯ͸ඇಉظʁ • ඇಉظॲཧΛಉظతͳײ֮Ͱखଓ͖తʹॻ͚Δ

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ίϧʔνϯ͸ඇಉظॲཧΛಉظ తʢखଓ͖తʣʹॻ͚Δ • ಉظతʹॻ͚ΔͷͰɺ௚ײతͰɺόάΛຒΊࠐΈ ʹ͍͘ɻ(σουϩοΫɾ࣮ߦλΠϛϯά໰୊) • ͳΜͱ͔Listener΍ίʔϧόοΫ஍ࠈ͔Βͷղ์ɻ

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async / await ΋͋Δ • async ίϧʔνϯͰɺඇಉظίϧʔνϯʹͭͭ͠ɺ ݁ՌΛ଴ͭ͜ͱ΋Ͱ͖Δ • async = ݁ՌΛड͚औΕΔػೳΛ΋ͭ launchɻ

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Kotlin ίϧʔνϯͷ جຊ͸͜Ε͚ͩ

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Kotlin Coroutineͷ ศརͳػೳͷ঺հ

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flow ίϧʔνϯ • flow = γʔέϯεͰॱ࣍݁ՌΛྲྀ͢ async. • Rx ObservableΛࢀߟʹ࡞ΒΕ͍ͯΔɻ • map(transform{}), flatMap,ϑΟϧλ,  ྫ֎෮ؼॲཧ(catch{}), εϨου੾Γସ͑, combineLatest, zip ͳͲ΋͋Δɻ

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Channels, produce, actor • Channel ͸ίϧʔνϯؒͷ૒ํ޲ͷσʔ λ΍ΓऔΓʹ͔ͭ͑ΔΦϒδΣΫτɻ • produce { } ... ࢠ͕ૹ৴ͯ͠਌͕ड৴͢Δ Ұํ޲νϟϯωϧΛ࡞Δίϧʔνϯɻ • actor { } ... ਌͕ૹ৴ͯ͠ࢠ͕ड৴͢ΔҰํ ޲νϟωϧΛ࡞Δίϧʔνϯɻ

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AndroidXͰ࢖͑Δศརͳػೳ • ViewModelScope • LifecycleScope • liveData { LiveDataScope -> Unit ... }: LiveData