Kotlin Coroutines & Android

Transcript

1. Kotlin Coroutines & Android Kenji Abe / @STAR_ZERO Android, Kotlin

   GDE Cookpad Inc.

2. This class was deprecated in API level 30. Use the

   standard java.util.concurrent or Kotlin concurrency utilities instead. AsyncTask

3. Title safe Actio n safe Kotlin Coroutines are the recommended

   solution for async code.

4. Coroutines

5. fun request(callback: (Data) -> Unit) { // Network access }

   fun loadData() { request { data -> show(data) } } Callback

6. fun loadData() { request1 { data1 -> request2 { data2

   -> request3 { data3 -> request4 { data4 -> request5 { data5 -> // ... } } } } } } Callback

7. suspend fun request(): String = withContext(Dispatchers.IO) { // Network access

   } suspend fun loadData() { val data = request() show(data) } Coroutines

8. suspend fun request(): String = withContext(Dispatchers.IO) { // Network access

   } suspend fun loadData() { val data = request() show(data) } Coroutines

9. suspend fun request(): String = withContext(Dispatchers.IO) { // Network access

   } suspend fun loadData() { val data = request() show(data) } Coroutines

10. suspend fun request(): String = withContext(Dispatchers.IO) { // Network access

    } suspend fun loadData() { val data = request() show(data) } Coroutines request show Background Thread

11. suspend fun request(): String = withContext(Dispatchers.IO) { // Network access

    } suspend fun loadData() { val data = request() show(data) } Coroutines request show Background Thread

12. suspend fun request(): String = withContext(Dispatchers.IO) { // Network access

    } suspend fun loadData() { val data = request() show(data) } Coroutines request show Background Thread 待機

13. suspend fun request(): String = withContext(Dispatchers.IO) { // Network access

    } suspend fun loadData() { val data = request() show(data) } Coroutines request show Background Thread

14. CoroutineDispatcher

15. CoroutineDispatcher Main IO Default UI Network & Disk CPU

16. suspend fun request(): String = withContext(Dispatchers.IO) { // ... }

    CoroutineDispatcher

17. suspend fun run() { withContext(Dispatchers.IO) { // ... } withContext(Dispatchers.Default)

    { // ... } withContext(Dispatchers.Main) { // ... } } CoroutineDispatcher

18. CoroutineScope / CoroutineBuilder

19. ० CoroutineScope ◦ Coroutineのライフサイクルの管理 ◦ キャンセルや例外処理の対応 ० CoroutineBuilder ◦ 新しくCoroutineを作成して実行する

    ◦ launch / async CoroutineScope / CoroutineBuilder

20. fun event() { request() } suspend fun request() { //

    ... } CoroutineScope / CoroutineBuilder

21. fun event() { request() } suspend fun request() { //

    ... } CoroutineScope / CoroutineBuilder Suspend function 'request' should be called only from a coroutine or another suspend function

22. val scope = CoroutineScope(Dispatchers.Main) fun event() { scope.launch { request()

    } } CoroutineScope / CoroutineBuilder

23. val scope = CoroutineScope(Dispatchers.Main) fun event() { scope.launch { request()

    } } CoroutineScope / CoroutineBuilder CoroutineScope 作成

24. val scope = CoroutineScope(Dispatchers.Main) fun event() { scope.launch { request()

    } } CoroutineScope / CoroutineBuilder Coroutine 作成

25. Cancellation

26. val job = scope.launch { request() } // ... job.cancel()

    // or scope.cancel() Cancellation

27. val job = scope.launch { while(true) { // ... println("Hello")

    } } // ... job.cancel() Cancellation

28. val job = scope.launch { while(true) { // ... println("Hello")

    } } // ... job.cancel() Cancellation Hello Hello Hello Hello Hello Hello . .

29. val job = scope.launch { while(isActive) { // ... println("Hello")

    } } // ... job.cancel() Cancellation キャンセルされているか確認

30. val job = scope.launch { while(isActive) { ensureActive() // ...

    println("Hello") } } // ... job.cancel() Cancellation キャンセルされている場合 CancellationException

31. async / await

32. suspend fun request(): Data { delay(3000) // ... } val

    time = measureTimeMillis { val data1 = request() val data2 = request() } println("time = $time") async / await

33. suspend fun request(): Data { delay(3000) // ... } val

    time = measureTimeMillis { val data1 = request() val data2 = request() } println("time = $time") async / await 約 6000 ms

34. val time = measureTimeMillis { val deferred1 = async {

    request() } val deferred2 = async { request() } val data1 = deferred1.await() val data2 = deferred2.await() } println("time = $time") async / await

35. val time = measureTimeMillis { val deferred1 = async {

    request() } val deferred2 = async { request() } val data1 = deferred1.await() val data2 = deferred2.await() } println("time = $time") async / await 処理開始して待たずに次へ

36. val time = measureTimeMillis { val deferred1 = async {

    request() } val deferred2 = async { request() } val data1 = deferred1.await() val data2 = deferred2.await() } println("time = $time") async / await 完了を待って結果を返す

37. val time = measureTimeMillis { val deferred1 = async {

    request() } val deferred2 = async { request() } val data1 = deferred1.await() val data2 = deferred2.await() } println("time = $time") async / await 約 3000 ms

38. Exception

39. val scope = CoroutineScope(Dispatchers.Default) scope.launch { throw IllegalStateException() } Exception

    ❌

40. val deferred = async { throw IllegalStateException() } deferred.await() Exception

    ❌

41. val handler = CoroutineExceptionHandler { _, throwable -> // ...

    } val scope = CoroutineScope(Dispatchers.Default + handler) scope.launch { throw IllegalStateException() } Exception

42. val handler = CoroutineExceptionHandler { _, throwable -> // ...

    } val scope = CoroutineScope(Dispatchers.Default + handler) scope.launch { throw IllegalStateException() } Exception

43. Flow

44. ० 複数の値 ० Cold Stream (Terminal operatorsで処理を開始) ० 様々なオペレーター Flow

45. fun createFlow(): Flow<Int> { return flow { (1..10).forEach { emit(it)

    } } } scope.launch { val flow = createFlow() flow.collect { println(it) } } Flow

46. fun createFlow(): Flow<Int> { return flow { (1..10).forEach { emit(it)

    } } } scope.launch { val flow = createFlow() flow.collect { println(it) } } Flow Flowを作成

47. fun createFlow(): Flow<Int> { return flow { (1..10).forEach { emit(it)

    } } } scope.launch { val flow = createFlow() flow.collect { println(it) } } Flow Flowはまだ動かない

48. fun createFlow(): Flow<Int> { return flow { (1..10).forEach { emit(it)

    } } } scope.launch { val flow = createFlow() flow.collect { println(it) } } Flow ここで動きだす

49. fun createFlow(): Flow<Int> { return flow { (1..10).forEach { emit(it)

    } } } scope.launch { val flow = createFlow() flow.collect { println(it) } } Flow 値を送信 emit された値が通知される

50. flow.map { it * it }.filter { it % 3

    == 0 }.collect { // ... } Flow

51. suspendCancellableCoroutine callbackFlow

52. suspend fun run() = suspendCancellableCoroutine<Response> { continuation -> request(object :

    Callback { override fun success(response: Response) { continuation.resume(response) } override fun failure(e: Exception) { continuation.resumeWithException(e) } }) continuation.invokeOnCancellation { cancel() } } suspendCancellableCoroutine

53. suspend fun run() = suspendCancellableCoroutine<Response> { continuation -> request(object :

    Callback { override fun success(response: Response) { continuation.resume(response) } override fun failure(e: Exception) { continuation.resumeWithException(e) } }) continuation.invokeOnCancellation { cancel() } } suspendCancellableCoroutine

54. suspend fun run() = suspendCancellableCoroutine<Response> { continuation -> request(object :

    Callback { override fun success(response: Response) { continuation.resume(response) } override fun failure(e: Exception) { continuation.resumeWithException(e) } }) continuation.invokeOnCancellation { cancel() } } suspendCancellableCoroutine suspend funの戻り値

55. suspend fun run() = suspendCancellableCoroutine<Response> { continuation -> request(object :

    Callback { override fun success(response: Response) { continuation.resume(response) } override fun failure(e: Exception) { continuation.resumeWithException(e) } }) continuation.invokeOnCancellation { cancel() } } suspendCancellableCoroutine throw Exception

56. suspend fun run() = suspendCancellableCoroutine<Response> { continuation -> request(object :

    Callback { override fun success(response: Response) { continuation.resume(response) } override fun failure(e: Exception) { continuation.resumeWithException(e) } }) continuation.invokeOnCancellation { cancel() } } suspendCancellableCoroutine Coroutineがキャンセルされた

57. fun run() = callbackFlow<Data> { val callback = object :

    Callback { override fun onReceive(data: Data) { offer(data) } } registerCallback(callback) awaitClose { unregisterCallback(callback) } } callbackFlow

58. fun run() = callbackFlow<Data> { val callback = object :

    Callback { override fun onReceive(data: Data) { offer(data) } } registerCallback(callback) awaitClose { unregisterCallback(callback) } } callbackFlow

59. fun run() = callbackFlow<Data> { val callback = object :

    Callback { override fun onReceive(data: Data) { offer(data) } } registerCallback(callback) awaitClose { unregisterCallback(callback) } } callbackFlow 値を送信

60. fun run() = callbackFlow<Data> { val callback = object :

    Callback { override fun onReceive(data: Data) { offer(data) } } registerCallback(callback) awaitClose { unregisterCallback(callback) } } callbackFlow キャンセルされるまで待機

61. Coroutines Android

62. Room

63. @Dao interface UserDao { @Query("SELECT * FROM user") suspend fun

    getAll(): List<User> } Room

64. @Dao interface UserDao { @Query("SELECT * FROM user") fun getAll():

    Flow<List<User>> } Room

65. WorkManager

66. class MyWorker( context: Context, params: WorkerParameters ) : CoroutineWorker(context, params)

    { override suspend fun doWork(): Result { val data = readData() upload(data) return Result.success() } } WorkManager

67. CoroutineScope

68. viewModelScope.launch { // ... } viewModelScope init Cancelled Active onCleared

69. lifecycleScope.launch { // ... } lifecycleScope onCreate onPause Cancelled Active

    onStart onResume onDestroy onStop init

70. lifecycleScope.launchWhenCreated { // ... } lifecycleScope onCreate onPause Cancelled Active

    onStart onResume onDestroy onStop init Pause

71. lifecycleScope.launchWhenStarted { // ... } lifecycleScope onCreate onPause Cancelled Pause

    onStart onResume onDestroy onStop init Active Pause

72. lifecycleScope.launchWhenResumed { // ... } lifecycleScope onCreate onPause onStart onResume

    onDestroy onStop init Cancelled Pause Active Pause

73. LiveData

74. val data: LiveData<String> = liveData { // ... emit("test") }

    LiveData

75. val data: LiveData<String> = liveData { // ... emit("test") }

    LiveData suspend

76. val data: LiveData<String> = liveData { // ... emit("test") }

    LiveData 値を送信

77. val data = MutableLiveData(0) val flow = data.asFlow() scope.launch {

    flow.collect { // ... } } LiveData

78. val data = MutableLiveData(0) val flow = data.asFlow() scope.launch {

    flow.collect { // ... } } LiveData LiveData → Flow

79. val flow = flow { // ... emit("test") } val

    liveData = flow.asLiveData() liveData.observe(this) { // ... } LiveData

80. val flow = flow { // ... emit("test") } val

    liveData = flow.asLiveData() liveData.observe(this) { // ... } LiveData Flow → LiveData

81. asLiveData vs lifecycleScope.launchWhenStarted

82. fun FusedLocationProviderClient.locationFlow() = callbackFlow<Location> { val callback = object :

    LocationCallback() { override fun onLocationResult(result: LocationResult?) { result ?: return try { offer(result.lastLocation) } catch(e: Exception) {} } } requestLocationUpdates(/* ... */) .addOnFailureListener { e -> close(e) // in case of exception, close the Flow } // clean up when Flow collection ends awaitClose { removeLocationUpdates(callback) } } asLiveData vs lifecycleScope.launchWhenStarted

83. myFlow.asLiveData().observe { // ... } lifecycleScope.launchWhenStarted { myFlow.collect { //

    ... } } asLiveData vs lifecycleScope.launchWhenStarted

84. asLiveData vs lifecycleScope.launchWhenStarted Activity onStart Active Active onStop asLiveData lifecycleScope.launchWhenStarted

    Observer: Flow: Active Active Collector: Flow:

85. asLiveData vs lifecycleScope.launchWhenStarted Activity onStart Active Active onStop asLiveData lifecycleScope.launchWhenStarted

    Cancelled Cancelled Observer: Flow: Observer: Flow: Active Active Paused Active Collector: Flow: Collector: Flow:

86. And more...

87. New feature

88. StateFlow

89. class ViewModel { private val _counter = MutableStateFlow(0) val counter:

    StateFlow<Int> = _counter fun increment() { _counter.value++ } } lifecycleScope.launchWhenStarted { viewModel.counter.collect { println(it) } } StateFlow

90. ० FlowのHot Stream ० 読み込み専用のStateFlow / 書込み可能なMutableStateFlow ० 様々なオペレーター StateFlow

91. MutableLiveData<T>: var value: T fun postValue(value: T) LiveData<T>: val value:

    T LiveData vs StateFlow MutableStateFlow<T>: var value: T StateFlow<T>: val value: T

92. LiveData vs StateFlow • Data Holder • LifecycleOwner • 同じ値も通知される

    • 初期値は通知されない • Transformations • Flow (Hot Stream) • CoroutineScope • 同じ値は通知されない • 初期値も通知 • オペレーター LiveData StateFlow

93. Appendix goo.gle/coroutines-posts • Coroutines: First things first • Cancellation in

    coroutines • Exceptions in Coroutines • The suspend modifier — Under the hood goo.gle/coroutines-101 • Coroutines 101 codelabs.developers.google.com • Use Kotlin Coroutines in your Android App • Learn advanced coroutines with Kotlin Flow and LiveData • Building a Kotlin extensions library

94. Thank you!