MVI with Jetpack Compose

At @Mobiconf 2019

Transcript

1. luca_nicolett MVI with Jetpack Compose
2. luca_nicolett About me • Luca • Italian • Android Engineer • Based in London • @Babylon Health
3. luca_nicolett Topics • MVI • Jetpack Compose
4. MVI luca_nicolett
5. luca_nicolett MVI VIEW INTENT MODEL T USER Updates Manipulates Interacts Sees
6. luca_nicolett MVI Core principles: • Unidirectional • Immutability • Reactiveness • Functional
7. luca_nicolett MVI
8. luca_nicolett MVI UI REDUCER BUSINESS 
 LOGIC Actions Events State UI 
 Listens STATE
9. luca_nicolett MVI SOMETHING REDUCER ACTION
 RELAY Actions State
 Updates STATE
 RELAY TRANSFORMERS Actions States Events
10. luca_nicolett MVI • Actions • Transformers • Reducers • States
11. luca_nicolett MVI The middleware • Works as a glue • Binds actions to transformers • Transformations to reducers • Actions to reducers
12. luca_nicolett MVI perform("rating selection") .on<ActionFeedbackAction.RatingSelected>() .withReducer(reducers::reduceRatingSelected)
13. luca_nicolett MVI perform("load logged in patient data") .on( LifecycleAction.Created::class.java, ProfileScreenAction.RetryConnection::class.java, ProfileScreenAction.MonitorReady::class.java ) .transform { transformers.loadPatient(this) } .withReducer(reducers::reduceLoggedInPatient)
14. luca_nicolett MVI perform("load logged in patient data") .on( LifecycleAction.Created::class.java, ProfileScreenAction.RetryConnection::class.java, ProfileScreenAction.MonitorReady::class.java ) .transform { transformers.loadPatient(this) } .withReducer(reducers::reduceLoggedInPatient)
15. luca_nicolett MVI How does it help? • Decoupling • Testing
16. luca_nicolett MVI
17. luca_nicolett MVI
18. luca_nicolett MVI Fragment Renderer Activity render()
19. luca_nicolett MVI private fun render(state: HomeScreenRedesignState) { loading_container .show(state.loadingState == LoadingState.Loading) unable_to_connect_error_container .show(state.loadingState == LoadingState.Error) /* ... */ }
20. luca_nicolett MVI fun View.show(isVisible: Boolean = true) { this.visibility = if (isVisible) View.VISIBLE else View.GONE }
21. luca_nicolett MVI private fun render(state: EditMoodState) { submitEditsButton?.isEnabled = state.hasAppliedChanges /* ... */ }
22. luca_nicolett MVI private fun render(state: AddMoodState) { if (state.showUrgentHelpDialog) { showUrgentHelpDialog() return } /* ... */ }
23. luca_nicolett MVI
24. Jetpack Compose luca_nicolett
25. luca_nicolett Jetpack Compose
26. luca_nicolett Jetpack Compose
27. luca_nicolett Jetpack Compose • Declarative UI • Concise & Idiomatic • Stateless or Stateful components • Reusable components • Compatible
28. luca_nicolett Jetpack Compose @Composable
 @GenerateView fun Greetings(name: String) { /* ... */ } <GreetingsView android:id="@+id/greetings" app:name="Luca" /> val greetingsView = findViewById<GreetingsView>(R.id.greetings) greetingsView.name = "Luca"
29. luca_nicolett Jetpack Compose @Composable
 @GenerateView fun Greetings(name: String) { /* ... */ } <GreetingsView android:id="@+id/greetings" app:name="Luca" /> val greetingsView = findViewById<GreetingsView>(R.id.greetings) greetingsView.name = "Luca"
30. luca_nicolett Jetpack Compose @Composable
 @GenerateView fun Greetings(name: String) { /* ... */ } <GreetingsView android:id="@+id/greetings" app:name="Luca" /> val greetingsView = findViewById<GreetingsView>(R.id.greetings) greetingsView.name = "Luca"
31. luca_nicolett Jetpack Compose • Declarative UI • Concise & Idiomatic • Stateless or Stateful components • Reusable components • Compatible • Unbundled from the OS
32. luca_nicolett Jetpack Compose
33. luca_nicolett Jetpack Compose mkdir ~/bin PATH=~/bin:$PATH curl https://storage.googleapis.com/git-repo-downloads/repo > ~/bin/repo chmod a+x ~/bin/repo
34. luca_nicolett Jetpack Compose mkdir androidx-master-dev cd androidx-master-dev repo init -u https://android.googlesource.com/platform/ manifest -b androidx-master-dev repo sync -j8 -c
35. luca_nicolett Jetpack Compose mkdir androidx-master-dev cd androidx-master-dev repo init -u https://android.googlesource.com/platform/ manifest -b androidx-master-dev repo sync -j8 -c Download the code (and grab a coffee while we pull down 6GB)
36. luca_nicolett Jetpack Compose cd path/to/checkout/frameworks/support/ ./studiow
37. luca_nicolett Jetpack Compose
38. luca_nicolett Jetpack Compose class MyActivity: Activity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContent { MyComposableFunction() } } }
39. luca_nicolett Jetpack Compose class MyActivity: Activity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContent { MyComposableFunction() } } }
40. luca_nicolett Jetpack Compose fun Activity.setContent(content: @Composable() () -> Unit) : CompositionContext? { /* ... */ }
41. luca_nicolett Jetpack Compose fun Activity.setContent(content: @Composable() () -> Unit) : CompositionContext? { val craneView = window.decorView .findViewById<ViewGroup>(android.R.id.content) .getChildAt(0) as? AndroidCraneView ?: AndroidCraneView(this) .also { setContentView(it) } val coroutineContext = Dispatchers.Main return Compose.composeInto(craneView.root, this) { WrapWithAmbients( craneView, this, coroutineContext ) {
42. luca_nicolett Jetpack Compose fun Activity.setContent(content: @Composable() () -> Unit) : CompositionContext? { val craneView = window.decorView .findViewById<ViewGroup>(android.R.id.content) .getChildAt(0) as? AndroidCraneView ?: AndroidCraneView(this) .also { setContentView(it) } val coroutineContext = Dispatchers.Main return Compose.composeInto(craneView.root, this) { WrapWithAmbients( craneView, this, coroutineContext ) {
43. luca_nicolett .findViewById<ViewGroup>(android.R.id.content) .getChildAt(0) as? AndroidCraneView ?: AndroidCraneView(this) .also { setContentView(it) } val coroutineContext = Dispatchers.Main return Compose.composeInto(craneView.root, this) { WrapWithAmbients( craneView, this, coroutineContext ) { content() } } } Jetpack Compose
44. luca_nicolett Jetpack Compose @Composable fun Greetings(name: String) { Text("Hello $name") }
45. luca_nicolett Jetpack Compose @Composable fun Text(/* ... */) { 
 /* ... */ Draw { canvas, _ -> internalSelection.value?.let { textDelegate.paintBackground( it.min, it.max, selectionColor, canvas ) } textDelegate.paint(canvas) }
 /* ... */ }
46. luca_nicolett Jetpack Compose @Composable fun Text(/* ... */) { 
 /* ... */ Draw { canvas, _ -> internalSelection.value?.let { textDelegate.paintBackground( it.min, it.max, selectionColor, canvas ) } textDelegate.paint(canvas) }
 /* ... */ }
47. luca_nicolett Jetpack Compose @Composable fun Text(/* ... */) { 
 /* ... */ Draw { canvas, _ -> internalSelection.value?.let { textDelegate.paintBackground( it.min, it.max, selectionColor, canvas ) } textDelegate.paint(canvas) 
 // Paints the text onto the given canvas. }
 /* ... */ }
48. luca_nicolett Jetpack Compose
49. luca_nicolett Jetpack Compose
50. luca_nicolett Jetpack Compose @Composable fun TextField(/* ... */) { // States val hasFocus = +state { false } val coords = +state<LayoutCoordinates?> { null } /* ... */ }
51. luca_nicolett Jetpack Compose @CheckResult("+") /* inline */ fun <T> state(init: () -> T) = memo { State(init()) }
52. luca_nicolett Jetpack Compose /** * The State class is an @Model class meant to * wrap around a single value. * It is used in the `+state` and `+stateFor` effects. */ @Model class State<T> @PublishedApi internal constructor(value:T) : Framed { /* ... */ }
53. luca_nicolett Jetpack Compose /** * [Model] can be applied to a class which represents your * application's data model, and will cause instances of the * class to become observable, such that a read of a property * of an instance of this class during the invocation of a * composable function will cause that component to be * "subscribed" to mutations of that instance. Composable * functions which directly or indirectly read properties * of the model class, the composables will be recomposed * whenever any properties of the the model are written to. */
54. luca_nicolett Jetpack Compose @Model data class TaskModel( var isDone: Boolean, val description: String )
55. luca_nicolett Jetpack Compose @Model data class TaskModel( var isDone: Boolean, val description: String ): BaseModel()
56. luca_nicolett Jetpack Compose @Model data class TaskModel( var isDone: Boolean, val description: String ): BaseModel() TaskModel.kt: (14, 3): Model objects do not support inheritance
57. luca_nicolett Jetpack Compose @Composable
 fun RallyBody() {
 Padding(padding = 16.dp) {
 Column {
 // TODO: scrolling container
 RallyAlertCard()
 HeightSpacer(height = 10.dp)
 RallyAccountsCard()
 }
 }
 }
58. luca_nicolett Jetpack Compose @Composable
 fun RallyBody() {
 Padding(padding = 16.dp) {
 VerticalScroller {
 Column {
 RallyAlertCard()
 HeightSpacer(height = 10.dp)
 RallyAccountsCard()
 }
 }
 } }
59. luca_nicolett Jetpack Compose
60. luca_nicolett Jetpack Compose
61. luca_nicolett Jetpack Compose @Composable fun DrawSeekBar(x: Float) { var paint = +memo { Paint() } Draw { canvas, parentSize -> /* ... */ canvas.drawRect(Rect(/* ... */), paint) canvas.drawRect(Rect(/* ... */), paint) canvas.drawCircle(/* ... */, paint) } }
62. luca_nicolett Jetpack Compose
63. luca_nicolett Jetpack Compose @Composable fun AlertDialog( onCloseRequest: () -> Unit, title: (@Composable() () -> Unit)? = null, text: (@Composable() () -> Unit), confirmButton: (@Composable() () -> Unit), dismissButton: (@Composable() () -> Unit)?, buttonLayout: AlertDialogButtonLayout ) { Dialog(onCloseRequest = onCloseRequest) { /* ... */ } }
64. luca_nicolett Jetpack Compose @Composable fun Dialog( onCloseRequest: () -> Unit, children: @Composable() () -> Unit ) { val context = +ambient(ContextAmbient) val dialog = +memo { DialogWrapper(context, onCloseRequest) } }
65. luca_nicolett Jetpack Compose @Composable fun Dialog( onCloseRequest: () -> Unit, children: @Composable() () -> Unit ) { +onActive { dialog.show() onDispose { dialog.dismiss() dialog.disposeComposition() } } }
66. luca_nicolett Jetpack Compose @Composable fun Dialog( onCloseRequest: () -> Unit, children: @Composable() () -> Unit ) { +onCommit { dialog.setContent(children) } }
67. luca_nicolett Jetpack Compose
68. luca_nicolett Jetpack Compose @Composable fun RippleRect() { val radius = withDensity(+ambientDensity()) { TargetRadius.toPx() 
 } val toState = +state { 
 ButtonStatus.Initial 
 } val rippleTransDef = +memo { 
 createTransDef(radius.value) 
 } val onPress: (PxPosition) -> Unit = 
 { position -> down.x = position.x.value
69. luca_nicolett val rippleTransDef = +memo { 
 createTransDef(radius.value) 
 } val onPress: (PxPosition) -> Unit = 
 { position -> down.x = position.x.value down.y = position.y.value toState.value = ButtonStatus.Pressed } val onRelease: () -> Unit = { toState.value = ButtonStatus.Released } PressGestureDetector(onPress = onPress, onRele Container(expanded = true) { Transition( definition = rippleTransDef, toState = toState.value Jetpack Compose
70. luca_nicolett val onRelease: () -> Unit = { toState.value = ButtonStatus.Released } PressGestureDetector( onPress = onPress, onRelease = onRelease ) { Container(expanded = true) { Transition( definition = rippleTransDef, toState = toState.value ) { state -> RippleRectFromState(state) } } } } Jetpack Compose
71. luca_nicolett @Composable fun RippleRectFromState(state: TransitionState) { // TODO: file bug for when "down" is not a 
 // file level val, it's not memoized 
 // correctly val x = down.x val y = down.y val paint = Paint().apply { color = Color( alpha = /* ... */ red = 0, green = 235, Jetpack Compose
72. luca_nicolett // file level val, it's not memoized 
 // correctly val x = down.x val y = down.y val paint = Paint().apply { color = Color( alpha = /* ... */ red = 0, green = 235, blue = 224 ) } val radius = state[radius] Draw { canvas, _ -> Jetpack Compose
73. luca_nicolett red = 0, green = 235, blue = 224 ) } val radius = state[radius] Draw { canvas, _ -> canvas.drawCircle(
 Offset(x, y), radius, paint
 ) } } Jetpack Compose
74. luca_nicolett Jetpack Compose @RunWith(JUnit4::class) @get:Rule val composeTestRule = createComposeRule() @Test
 fun topAppBar_expandsToScreen() {
 val dm = composeTestRule.displayMetrics
 composeTestRule
 .setMaterialContentAndCollectSizes {
 TopAppBar<Nothing>()
 }
 .assertHeightEqualsTo(appBarHeight)
 .assertWidthEqualsTo { dm.widthPixels.ipx } }
75. luca_nicolett Jetpack Compose @RunWith(JUnit4::class) @get:Rule val composeTestRule = createComposeRule() @Test
 fun topAppBar_expandsToScreen() {
 val dm = composeTestRule.displayMetrics
 composeTestRule
 .setMaterialContentAndCollectSizes {
 TopAppBar<Nothing>()
 }
 .assertHeightEqualsTo(appBarHeight)
 .assertWidthEqualsTo { dm.widthPixels.ipx } }
76. luca_nicolett Jetpack Compose @RunWith(JUnit4::class) @get:Rule val composeTestRule = createComposeRule() @Test
 fun topAppBar_expandsToScreen() {
 val dm = composeTestRule.displayMetrics
 composeTestRule
 .setMaterialContentAndCollectSizes {
 TopAppBar<Nothing>()
 }
 .assertHeightEqualsTo(appBarHeight)
 .assertWidthEqualsTo { dm.widthPixels.ipx } }
77. All together luca_nicolett
78. luca_nicolett All together OOP approach Functional approach
79. All together Object Oriented luca_nicolett
80. luca_nicolett All together interface BaseViewState { @Composable fun buildUI() }
81. luca_nicolett All together object InProgress : BaseViewState(true, null) { @Composable override fun buildUI() { Container(expanded = true) { CircularProgressIndicator() } } }
82. luca_nicolett All together override fun onCreate(savedInstanceState: Bundle?) {
 super.onCreate(savedInstanceState)
 viewModel = /* view model init */
 setContent {
 CustomTheme {
 render(viewModel.states())
 }
 }
 /* .. */
 }
83. luca_nicolett All together override fun onCreate(savedInstanceState: Bundle?) {
 super.onCreate(savedInstanceState)
 viewModel = /* view model init */
 setContent {
 CustomTheme {
 render(viewModel.states())
 }
 }
 /* .. */
 }
84. luca_nicolett All together override fun onCreate(savedInstanceState: Bundle?) {
 super.onCreate(savedInstanceState)
 viewModel = /* view model init */
 setContent {
 CustomTheme {
 render(viewModel.states())
 }
 }
 /* .. */
 }
85. luca_nicolett All together override fun onCreate(savedInstanceState: Bundle?) {
 super.onCreate(savedInstanceState)
 viewModel = /* view model init */
 setContent {
 CustomTheme {
 render(viewModel.states())
 }
 }
 /* .. */
 }
86. luca_nicolett All together override fun render( observableState: Observable<BaseViewState> ) { val state = +observe(ViewState.Idle, observableState) state.buildUI() }
87. luca_nicolett All together override fun render( observableState: Observable<BaseViewState> ) { val state = +observe(ViewState.Idle, observableState) state.buildUI() }
88. luca_nicolett All together override fun render( observableState: Observable<BaseViewState> ) { val state = +observe(ViewState.Idle, observableState) state.buildUI() }
89. luca_nicolett All together fun <T> observe(initialState: T, data: Observable<T>) = effectOf<T> { val result = +state { initialState } +onActive { val disposable = data.subscribe { newValue -> result.value = newValue } onDispose { disposable.dispose() } } } return result.value }
90. luca_nicolett All together fun <T> observe(initialState: T, data: Observable<T>) = effectOf<T> { val result = +state { initialState } +onActive { val disposable = data.subscribe { newValue -> result.value = newValue } onDispose { disposable.dispose() } } } return result.value }
91. luca_nicolett All together fun <T> observe(initialState: T, data: Observable<T>) = effectOf<T> { val result = +state { initialState } +onActive { val disposable = data.subscribe { newValue -> result.value = newValue } onDispose { disposable.dispose() } } } return result.value }
92. luca_nicolett All together fun <T> observe(initialState: T, data: Observable<T>) = effectOf<T> { val result = +state { initialState } +onActive { val disposable = data.subscribe { newValue -> result.value = newValue } onDispose { disposable.dispose() } } } return result.value }
93. luca_nicolett All together fun <T> observe(initialState: T, data: Observable<T>) = effectOf<T> { val result = +state { initialState } +onActive { val disposable = data.subscribe { newValue -> result.value = newValue } onDispose { disposable.dispose() } } } return result.value }
94. luca_nicolett All together fun <T> observe(initialState: T, data: Observable<T>) = effectOf<T> { val result = +state { initialState } +onActive { val disposable = data.subscribe { newValue -> result.value = newValue } onDispose { disposable.dispose() } } } return result.value }
95. All together Functional luca_nicolett
96. luca_nicolett All together override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) // viewModel = /* ... */ not needed anymore setContent { PostListScreen( processIntents(intents()), reloadPostListIntentPublisher ) } }
97. luca_nicolett All together override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) // viewModel = /* ... */ not needed anymore setContent { PostListScreen( processIntents(intents()), reloadPostListIntentPublisher ) } }
98. luca_nicolett All together override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) // viewModel = /* ... */ not needed anymore setContent { PostListScreen( processIntents(intents()), reloadPostListIntentPublisher ) } }
99. luca_nicolett All together override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) // viewModel = /* ... */ not needed anymore setContent { PostListScreen( processIntents(intents()), reloadPostListIntentPublisher ) } }
100. luca_nicolett All together override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) // viewModel = /* ... */ not needed anymore setContent { PostListScreen( processIntents(intents()), reloadPostListIntentPublisher ) } }
101. luca_nicolett All together fun processIntents(intents: Observable<PostListIntent>): PostListViewState { intents.subscribe(intentsObserver) return modelState()
 } }
102. luca_nicolett All together fun modelState() = +effectOf<PostListViewState> { val result = +state { PostListViewState.Idle } var disposable: Disposable? = null +onActive { disposable = intentsObserver .applyBusinessLogic() .subscribe { result.value = it } } +onDispose { disposable?.dispose() } result.value
103. luca_nicolett All together fun modelState() = +effectOf<PostListViewState> { val result = +state { PostListViewState.Idle } var disposable: Disposable? = null +onActive { disposable = intentsObserver .applyBusinessLogic() .subscribe { result.value = it } } +onDispose { disposable?.dispose() } result.value
104. luca_nicolett fun modelState() = +effectOf<PostListViewState> { val result = +state { PostListViewState.Idle } var disposable: Disposable? = null +onActive { disposable = intentsObserver .applyBusinessLogic() .subscribe { result.value = it } } +onDispose { disposable?.dispose() } result.value } All together
105. luca_nicolett fun modelState() = +effectOf<PostListViewState> { val result = +state { PostListViewState.Idle } var disposable: Disposable? = null +onActive { disposable = intentsObserver .applyBusinessLogic() .subscribe { result.value = it } } +onDispose { disposable?.dispose() } result.value } All together
106. luca_nicolett fun modelState() = +effectOf<PostListViewState> { val result = +state { PostListViewState.Idle } var disposable: Disposable? = null +onActive { disposable = intentsObserver .applyBusinessLogic() .subscribe { result.value = it } } +onDispose { disposable?.dispose() } result.value } All together
107. luca_nicolett All together override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) // viewModel = /* ... */ not needed anymore setContent { PostListScreen( processIntents(intents()) ) } }
108. luca_nicolett All together @Composable fun PostListScreen( state: PostListViewState ) { when (state) { PostListViewState.InProgress -> { Container(expanded = true) { CircularProgressIndicator() } } /* ... */ } }
109. luca_nicolett All together PostListScreen(processIntents(intents()))
110. luca_nicolett All together
111. luca_nicolett All together PostListScreen( processIntents( intents() ) )
112. luca_nicolett References MVI http://hannesdorfmann.com/android/model-view-intent https://www.novatec-gmbh.de/en/blog/mvi-in-android/ https://cycle.js.org/model-view-intent.html Jetpack Compose https://www.youtube.com/watch?v=VsStyq4Lzxo https://medium.com/q42-engineering/android-jetpack-compose-895b7fd04bf4 https://blog.karumi.com/android-jetpack-compose-review
113. luca_nicolett Thank you!
114. luca_nicolett Questions?