Kotlin Coroutines & Android

https://developersonair.withgoogle.com/events/a11meetups-jp?talk=kotlin

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!