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Managing State Beyond
ViewModels and Hilt
September 15th, 2023
Ralf Wondratschek
@vRallev | @[email protected] | @ralf_dev
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Background
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Background
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Background
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Background
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https://www.youtube.com/watch?v=xESX82kwjn4
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No content
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https://www.youtube.com/watch?v=0T_zvUEqsD4
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Old architecture
class Application
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Old architecture
class Application
class AbcActivity class DefActivity
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Old architecture
class Application
class GhiFragment class JklFragment
class AbcActivity class DefActivity
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Old architecture
class Application
class AbcViewModel class DefViewModel class GhiFragment
class GhiViewModel
class JklFragment
class JklViewModel
class AbcActivity class DefActivity
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Old architecture - Bottlenecks
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Old architecture - Bottlenecks
● Driven by Android and its window management and not by business logic
● Different lifecycles with different teardown hooks
● Custom lifecycles like user scope adjacent
● Coroutine scopes provided by Android components
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Old architecture - Lifecycle
Lifecycle managed by us
Lifecycle managed by Android
Business Logic
UI rendering
Activity Fragment
ViewModel ViewModel
flow: Flow
operation()
flow: Flow
operation()
Service objects
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Old architecture - Lifecycle
class RouteViewModel : ViewModel() {
fun sendRequest() {
viewModelScope.launch {
httpClient.post(request)
}
}
}
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Old architecture - Lifecycle
class RouteViewModel : ViewModel() {
fun sendRequest() {
viewModelScope.launch {
httpClient.post(request)
}
}
}
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Old architecture - Lifecycle
class Application : Context {
open fun onCreate() = Unit
}
class Activity : Context {
open fun onCreate(..) = Unit
open fun onDestroy() = Unit
}
class Fragment {
open fun onCreate(..) = Unit
open fun onDestroy() = Unit
}
class ViewModel {
open fun onCleared() = Unit
}
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Old architecture - Lifecycle
interface Application.ActivityLifecycleCallbacks {
...
}
interface DefaultLifecycleObserver {
...
}
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Old architecture - Without unidirectional dataflow
● Challenges synchronizing multiple screens
● No holistic overview of the state of the application
● Way too easy to mix business logic with UI code
● Many services pushed into application scope
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Old architecture - Without unidirectional dataflow
Lifecycle managed by us
Lifecycle managed by Android
Business Logic
UI rendering
Activity Fragment
ViewModel ViewModel
flow: Flow
operation()
flow: Flow
operation()
Service objects
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Old architecture - Without unidirectional dataflow
ViewModel
Activity
operation1()
operation2()
operation3()
flow1: Flow
flow2: Flow
flow3: Flow
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Old architecture - Anti-pattern
class AmazonApplication : Application() {
@Inject lateinit var routingRepository: RoutingRepository
@Inject lateinit var locationProvider: LocationProvider
override fun onCreate() {
super.onCreate()
routingRepository.initialize()
locationProvider.initialize()
}
}
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Old architecture - Anti-pattern
interface RoutingRepository {
fun initialize()
suspend fun loadRoute (): Route
}
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Old architecture - Anti-pattern
class AmazonRoutingRepository @Inject constructor(
@IODispatcher dispatcher: CoroutineDispatcher
) : RoutingRepository {
private val coroutineScope = CoroutineScope(dispatcher)
override fun initialize() {
coroutineScope.launch {
// Initialize
}
}
override suspend fun loadRoute(): Route = ...
}
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Old architecture - Anti-pattern
class AmazonRoutingRepository @Inject constructor(
@IODispatcher dispatcher: CoroutineDispatcher
) : RoutingRepository {
private val coroutineScope = CoroutineScope(dispatcher)
override fun initialize() {
coroutineScope.launch {
// Initialize
}
}
override suspend fun loadRoute(): Route = ...
}
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Old architecture - Anti-pattern
class FakeRoutingRepository @Inject constructor() : RoutingRepository {
override fun initialize() = Unit
override suspend fun loadRoute(): Route = ...
}
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Old architecture - Hilt
● Strong coupling to Android components
● Custom components with limitations
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Old architecture - Hilt
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Goals
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Goals
● Strongly decouple business logic from Android lifecycle
● Features are device agnostic
● Avoid thread and memory leaks
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Design principles - Modular design
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Design principles - Modular design
class AmazonApplication : Application() {
@Inject lateinit var routingRepository: RoutingRepository
@Inject lateinit var locationProvider: LocationProvider
override fun onCreate() {
super.onCreate()
routingRepository.initialize()
locationProvider.initialize()
}
}
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Design principles - Composition over inheritance
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Design principles - Composition over inheritance
AppCompatActivity
BaseActivity
InfoActivity
ViewModel
BaseViewModel
InfoViewModel
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Design principles - Dependency inversion by default
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Design principles - Dependency inversion by default
interface RoutingRepository {
fun initialize()
suspend fun loadRoute (): Route
}
class AmazonRoutingRepository @Inject constructor() : RoutingRepository {
override fun initialize() = ...
override suspend fun loadRoute(): Route = ...
}
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Design principles - Dependency inversion by default
interface RoutingRepository {
fun initialize()
suspend fun loadRoute (): Route
}
class AmazonRoutingRepository @Inject constructor() : RoutingRepository {
override fun initialize() = ...
override suspend fun loadRoute(): Route = ...
}
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Design principles - Inject dependencies
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Design principles - Inject dependencies
class AmazonRoutingRepository @Inject constructor(
@IODispatcher dispatcher: CoroutineDispatcher
) : RoutingRepository {
private val coroutineScope = CoroutineScope(dispatcher)
override fun initialize() {
coroutineScope.launch {
// Initialize
}
}
override suspend fun loadRoute(): Route = ...
}
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Design principles - Inject dependencies
class AmazonRoutingRepository @Inject constructor(
@IODispatcher dispatcher: CoroutineDispatcher
) : RoutingRepository {
private val coroutineScope = CoroutineScope(dispatcher)
override fun initialize() {
coroutineScope.launch {
// Initialize
}
}
override suspend fun loadRoute(): Route = ...
}
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Design principles - Unidirectional dataflow to drive UI
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Design principles - Unidirectional dataflow to drive UI
ViewModel
Activity
operation1()
operation2()
operation3()
flow1: Flow
flow2: Flow
flow3: Flow
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From Hilt to Anvil
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From Hilt to Anvil
https://www.droidcon.com/2022/06/28/dagger-anvil-learning-to-love-dependency-injection/
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From Hilt to Anvil
@Module
@ContributesTo(AppScope::class)
object RouteModule
@Module
@ContributesTo(AppScope::class, replaces = [RouteModule::class])
object TestRouteModule
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From Hilt to Anvil
interface RoutingRepository {
suspend fun loadRoute (): Route
}
@ContributesBinding(scope = AppScope::class)
class AmazonRoutingRepository @Inject constructor() : RoutingRepository {
override suspend fun loadRoute(): Route = ...
}
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From Hilt to Anvil
interface RoutingRepository {
suspend fun loadRoute (): Route
}
@ContributesBinding(scope = AppScope::class)
class AmazonRoutingRepository @Inject constructor() : RoutingRepository {
override suspend fun loadRoute(): Route = ...
}
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From Hilt to Anvil
@Module
@InstallIn(ActivityComponent::class)
@ContributesTo(ActivityScope::class)
class RouteModule
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From Hilt to Anvil
class AmazonRoutingRepository @Inject constructor(
@ApplicationContext context: Context
application: Application
) : RoutingRepository
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From Hilt to Anvil
@Binds
abstract fun bindRoutingRepository(
repository: AmazonRoutingRepository
): RoutingRepository
@ContributesBinding(AppScope::class)
class AmazonRoutingRepository @Inject constructor(
application: Application
) : RoutingRepository
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From Hilt to Anvil
class AmazonApplication : Application() {
lateinit var component: AppComponent
override fun onCreate() {
super.onCreate()
component = DaggerAppComponent.factory().create(applicationContext = this)
component.inject(this)
}
}
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From Hilt to Anvil
class OpenSourceActivity : Activity() {
private val viewModelFactory by viewModels()
private val viewModel by viewModels { viewModelFactory }
...
}
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From Hilt to Anvil
class ViewModelFactory(
application: Application
) : ViewModelProvider.Factory, AndroidViewModel(application) {
private val viewModels: Map, @JvmSuppressWildcards Provider>
init {
val component = application.component.createViewModelComponent()
viewModels = component.viewModels()
}
override fun create(modelClass: Class): T {
@Suppress("UNCHECKED_CAST")
return viewModels.getValue(modelClass).get() as T
}
override fun onCleared() {
// Clean up any resources
}
}
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From Hilt to Anvil
class ViewModelFactory(
application: Application
) : ViewModelProvider.Factory, AndroidViewModel(application) {
private val viewModels: Map, @JvmSuppressWildcards Provider>
init {
val component = application.component.createViewModelComponent()
viewModels = component.viewModels()
}
override fun create(modelClass: Class): T {
@Suppress("UNCHECKED_CAST")
return viewModels.getValue(modelClass).get() as T
}
override fun onCleared() {
// Clean up any resources
}
}
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From Hilt to Anvil
class ViewModelFactory(
application: Application
) : ViewModelProvider.Factory, AndroidViewModel(application) {
private val viewModels: Map, @JvmSuppressWildcards Provider>
init {
val component = application.component.createViewModelComponent()
viewModels = component.viewModels()
}
override fun create(modelClass: Class): T {
@Suppress("UNCHECKED_CAST")
return viewModels.getValue(modelClass).get() as T
}
override fun onCleared() {
// Clean up any resources
}
}
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From Hilt to Anvil
class ViewModelFactory(
application: Application
) : ViewModelProvider.Factory, AndroidViewModel(application) {
private val viewModels: Map, @JvmSuppressWildcards Provider>
init {
val component = application.component.createViewModelComponent()
viewModels = component.viewModels()
}
override fun create(modelClass: Class): T {
@Suppress("UNCHECKED_CAST")
return viewModels.getValue(modelClass).get() as T
}
override fun onCleared() {
// Clean up any resources
}
}
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From Hilt to Anvil
@ContributesMultibinding(ViewModelScope::class)
@ViewModelKey(OpenSourceViewModel::class)
class OpenSourceViewModel @Inject constructor(
...
) : ViewModel() {
...
}
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Scope
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Scope
“Scopes define the boundary software components operate in. A scope is a space with a
well-defined lifecycle that can be created and torn down. Scopes host other objects and can
bind them to their lifecycle. Sub-scopes or child scopes have the same or a shorter lifecycle
as their parent scope.”
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Scope
“Scopes define the boundary software components operate in. A scope is a space with a
well-defined lifecycle that can be created and torn down. Scopes host other objects and can
bind them to their lifecycle. Sub-scopes or child scopes have the same or a shorter lifecycle
as their parent scope.”
– Ralf Wondratschek
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Scope
● Android components as scope?
● Coroutine scopes?
● Dagger components as scope?
● Implement your own?
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Scope
interface Scope {
val name: String
val parent: Scope?
fun buildChild(name: String, builder: (Builder.() -> Unit)? = null): Scope
fun children(): Set
fun register(scoped: Scoped)
fun isDestroyed(): Boolean
fun destroy()
fun getService(key: String): T?
}
https://github.com/square/mortar/blob/master/mortar/src/main/java/mortar/MortarScope.java
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Scope
class Builder internal constructor(
private val name: String,
private val parent: Scope?
) {
private val services = mutableMapOf()
fun addService(key: String, service: Any) {
services[key] = service
}
internal fun build(): Scope {
return ScopeImpl(name, parent, services)
}
}
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Scope - Services
interface Scope {
fun getService(key: String): T?
}
inline fun Scope.daggerComponent(): T {
return ...
}
fun Scope.Builder.addDaggerComponent(component: Any) {
addService(DAGGER_COMPONENT_KEY, component)
}
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Scope - Services
interface Scope {
fun getService(key: String): T?
}
inline fun Scope.daggerComponent(): T {
return ...
}
fun Scope.Builder.addDaggerComponent(component: Any) {
addService(DAGGER_COMPONENT_KEY, component)
}
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Scope - Services
private const val COROUTINE_SCOPE_KEY = "coroutineScope"
fun Scope.coroutineScope(context: CoroutineContext? = null): CoroutineScope {
val result = checkNotNull(getService(COROUTINE_SCOPE_KEY)) {
"Couldn't find CoroutineScopeScoped within scope $name."
}
check(result.isActive) {
"Expected the coroutine scope ${result.coroutineContext[CoroutineName]?.name} " +
"still to be active."
}
return result.createChild(context)
}
fun Scope.Builder.addCoroutineScope(coroutineScope: CoroutineScopeScoped) {
addService(COROUTINE_SCOPE_KEY, coroutineScope)
}
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Scope - Services
private const val COROUTINE_SCOPE_KEY = "coroutineScope"
fun Scope.coroutineScope(context: CoroutineContext? = null): CoroutineScope {
val result = checkNotNull(getService(COROUTINE_SCOPE_KEY)) {
"Couldn't find CoroutineScopeScoped within scope $name."
}
check(result.isActive) {
"Expected the coroutine scope ${result.coroutineContext[CoroutineName]?.name} " +
"still to be active."
}
return result.createChild(context)
}
fun Scope.Builder.addCoroutineScope(coroutineScope: CoroutineScopeScoped) {
addService(COROUTINE_SCOPE_KEY, coroutineScope)
}
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Scope - Services
private const val COROUTINE_SCOPE_KEY = "coroutineScope"
fun Scope.coroutineScope(context: CoroutineContext? = null): CoroutineScope {
val result = checkNotNull(getService(COROUTINE_SCOPE_KEY)) {
"Couldn't find CoroutineScopeScoped within scope $name."
}
check(result.isActive) {
"Expected the coroutine scope ${result.coroutineContext[CoroutineName]?.name} " +
"still to be active."
}
return result.createChild(context)
}
fun Scope.Builder.addCoroutineScope(coroutineScope: CoroutineScopeScoped) {
addService(COROUTINE_SCOPE_KEY, coroutineScope)
}
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Scope - Services
rootScope = Scope.buildRootScope {
addDaggerComponent(createDaggerComponent())
}
application.rootScope
.buildChild(name = this::class.java.simpleName) {
addDaggerComponent(
application.rootScope
.daggerComponent()
.createActivityComponent()
)
}
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Scope - Hierarchy
AppScope
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Scope - Hierarchy
AppScope
UserScope LoggedOutScope
ActivityScope
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Scope - Hierarchy in reality
AppScope
UserScope ActivityScope ViewModelScope
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Scope - Callback
interface Scope {
fun register(scoped: Scoped)
}
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Scope - Callback
interface Scope {
fun register(scoped: Scoped)
}
interface Scoped {
fun onEnterScope(scope: Scope) = Unit
fun onExitScope() = Unit
}
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Scope - Callback
interface RoutingRepository {
fun initialize()
suspend fun loadRoute (): Route
}
class AmazonRoutingRepository : RoutingRepository {
override fun initialize() = ...
override suspend fun loadRoute(): Route = ...
}
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Scope - Callback
interface RoutingRepository {
suspend fun loadRoute (): Route
}
class AmazonRoutingRepository : RoutingRepository, Scoped {
override fun onEnterScope(scope: Scope) {
scope.coroutineScope().launch {
...
}
}
override suspend fun loadRoute(): Route = ...
}
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Scope - Callback
interface RoutingRepository {
suspend fun loadRoute (): Route
}
class AmazonRoutingRepository : RoutingRepository, Scoped {
override fun onEnterScope(scope: Scope) {
scope.coroutineScope().launch {
...
}
}
override suspend fun loadRoute(): Route = ...
}
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Scope - Callback
interface RoutingRepository {
suspend fun loadRoute (): Route
}
class AmazonRoutingRepository : RoutingRepository, Scoped {
override fun onEnterScope(scope: Scope) {
scope.coroutineScope().launch {
...
}
}
override suspend fun loadRoute(): Route = ...
}
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Scope - Callback
interface RoutingRepository {
suspend fun loadRoute (): Route
}
@ContributesMultibindingScoped(AppScope::class)
class AmazonRoutingRepository : RoutingRepository, Scoped {
override fun onEnterScope(scope: Scope) {
scope.coroutineScope().launch {
...
}
}
override suspend fun loadRoute(): Route = ...
}
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Scope - Callback
interface RoutingRepository {
suspend fun loadRoute (): Route
}
@ContributesMultibindingScoped(AppScope::class)
class AmazonRoutingRepository : RoutingRepository, Scoped {
override fun onEnterScope(scope: Scope) {
scope.coroutineScope().launch {
...
}
}
override suspend fun loadRoute(): Route = ...
}
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Scope - Callback
@ContributesTo(AppScope::class)
interface Component {
@ForScope(AppScope::class)
fun appScopedInstances(): Set
}
rootScope = Scope.buildRootScope {
addDaggerComponent(createDaggerComponent())
}
rootScope.register(rootScope.daggerComponent().appScopedInstances())
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Scope - Callback
@SingleIn(AppScope::class)
@ContributesMultibindingScoped(AppScope::class)
class ActivityListener @Inject constructor(
private val application: Application
) : Scoped {
val startedActivities: StateFlow> = ...
private val listener = object : Application.ActivityLifecycleCallbacks {
...
}
override fun onEnterScope(scope: Scope) {
application.registerActivityLifecycleCallbacks(listener)
}
override fun onExitScope() {
application.unregisterActivityLifecycleCallbacks(listener)
}
}
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Scope - Callback
@SingleIn(AppScope::class)
@ContributesMultibindingScoped(AppScope::class)
class ActivityListener @Inject constructor(
private val application: Application
) : Scoped {
val startedActivities: StateFlow> = ...
private val listener = object : Application.ActivityLifecycleCallbacks {
...
}
override fun onEnterScope(scope: Scope) {
application.registerActivityLifecycleCallbacks(listener)
}
override fun onExitScope() {
application.unregisterActivityLifecycleCallbacks(listener)
}
}
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Scope - Callback
@SingleIn(AppScope::class)
@ContributesMultibindingScoped(AppScope::class)
class ActivityListener @Inject constructor(
private val application: Application
) : Scoped {
val startedActivities: StateFlow> = ...
private val listener = object : Application.ActivityLifecycleCallbacks {
...
}
override fun onEnterScope(scope: Scope) {
application.registerActivityLifecycleCallbacks(listener)
}
override fun onExitScope() {
application.unregisterActivityLifecycleCallbacks(listener)
}
}
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Scope - Callback
@SingleIn(AppScope::class)
@ContributesMultibindingScoped(AppScope::class)
class QeCommandReceiver @Inject constructor(
private val application: Application,
) : BroadcastReceiver(), Scoped {
override fun onEnterScope(scope: Scope) {
application.registerReceiver(this, IntentFilter("..."))
}
override fun onExitScope() {
application.unregisterReceiver(this)
}
override fun onReceive(context: Context, intent: Intent) {
when (intent.getStringExtra("cmd")) {
...
}
}
}
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Scope - Callback
@SingleIn(AppScope::class)
@ContributesMultibindingScoped(AppScope::class)
class QeCommandReceiver @Inject constructor(
private val application: Application,
) : BroadcastReceiver(), Scoped {
override fun onEnterScope(scope: Scope) {
application.registerReceiver(this, IntentFilter("..."))
}
override fun onExitScope() {
application.unregisterReceiver(this)
}
override fun onReceive(context: Context, intent: Intent) {
when (intent.getStringExtra("cmd")) {
...
}
}
}
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Scope - Callback
@SingleIn(AppScope::class)
@ContributesMultibindingScoped(AppScope::class)
class QeCommandReceiver @Inject constructor(
private val application: Application,
) : BroadcastReceiver(), Scoped {
override fun onEnterScope(scope: Scope) {
application.registerReceiver(this, IntentFilter("..."))
}
override fun onExitScope() {
application.unregisterReceiver(this)
}
override fun onReceive(context: Context, intent: Intent) {
when (intent.getStringExtra("cmd")) {
...
}
}
}
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Scope - Callback
@SingleIn(AppScope::class)
@ContributesMultibindingScoped(AppScope::class)
class QeCommandReceiver @Inject constructor(
private val application: Application,
) : BroadcastReceiver(), Scoped {
override fun onEnterScope(scope: Scope) {
application.registerReceiver(this, IntentFilter("..."))
}
override fun onExitScope() {
application.unregisterReceiver(this)
}
override fun onReceive(context: Context, intent: Intent) {
when (intent.getStringExtra("cmd")) {
...
}
}
}
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Scope - Constructor?
If a class part of DriverSessionScope implements Scoped and injects DriverSessionService (which is
app-scoped), then we end up in a livelock and the app freezes. There is nothing wrong with this setup and it should be
supported.
The chain of events is as follows: the app scope gets created and someone injects DriverSessionService. Dagger
attempts to create DriverSessionService. In the constructor the service immediately creates the
DriverSessionScope, when the driver is already logged in. As part of this routine the service injects all Scoped
instances contributed to the DriverSessionScope. If one of these instances injects DriverSessionService (again,
from the app scope and that's valid), then Dagger cannot provide the DriverSessionService, because the previous
instance hasn't been created yet and is still in the constructor call. Therefore, Dagger creates another
DriverSessionService and the whole loop repeats.
TL;DR: Don't run any logic in the constructor.
The solution is implementing Scoped and moving all logic from the constructor call into onEnterScope().
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Scope - Constructor?
If a class part of DriverSessionScope implements Scoped and injects DriverSessionService (which is
app-scoped), then we end up in a livelock and the app freezes. There is nothing wrong with this setup and it should be
supported.
The chain of events is as follows: the app scope gets created and someone injects DriverSessionService. Dagger
attempts to create DriverSessionService. In the constructor the service immediately creates the
DriverSessionScope, when the driver is already logged in. As part of this routine the service injects all Scoped
instances contributed to the DriverSessionScope. If one of these instances injects DriverSessionService (again,
from the app scope and that's valid), then Dagger cannot provide the DriverSessionService, because the previous
instance hasn't been created yet and is still in the constructor call. Therefore, Dagger creates another
DriverSessionService and the whole loop repeats.
TL;DR: Don't run any logic in the constructor.
The solution is implementing Scoped and moving all logic from the constructor call into onEnterScope().
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Scope - Tests
@Test
fun `test routing repository registers for push updates`() {
val repository = AmazonRoutingRepository()
repository.onEnterScope(Scope.buildTestScope())
...
}
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Scope - Tests
fun Scope.Companion.buildTestScope(
name: String = "test",
context: CoroutineContext? = null,
builder: (Scope.Builder.() -> Unit)? = null
): Scope {
var coroutineContext = SupervisorJob() + UnconfinedTestDispatcher() + CoroutineName(name)
if (context != null) {
coroutineContext += context
}
val coroutineScope = CoroutineScopeScoped(coroutineContext)
val scope = buildRootScope(name = name) {
addCoroutineScopeScoped(coroutineScope)
builder?.invoke(this)
}
scope.register(coroutineScope)
return scope
}
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Scope - Recap
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Scope - Recap
class RouteViewModel : ViewModel() {
fun sendRequest() {
viewModelScope.launch {
httpClient.post(request)
}
}
}
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Scope - Recap
class RouteViewModel : ViewModel() {
fun sendRequest() {
viewModelScope.launch {
httpClient.post(request)
}
}
}
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Scope - Recap
class Application : Context {
open fun onCreate() = Unit
}
class Activity : Context {
open fun onCreate(..) = Unit
open fun onDestroy() = Unit
}
class Fragment {
open fun onCreate(..) = Unit
open fun onDestroy() = Unit
}
class ViewModel {
open fun onCleared() = Unit
}
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Scope - Recap
class Application : Context {
open fun onCreate() = Unit
}
class Activity : Context {
open fun onCreate(..) = Unit
open fun onDestroy() = Unit
}
class Fragment {
open fun onCreate(..) = Unit
open fun onDestroy() = Unit
}
class ViewModel {
open fun onCleared() = Unit
}
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Scope - Recap
class AmazonApplication : Application() {
@Inject lateinit var routingRepository: RoutingRepository
@Inject lateinit var locationProvider: LocationProvider
override fun onCreate() {
super.onCreate()
routingRepository.initialize()
locationProvider.initialize()
}
}
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Scope - Recap
class AmazonApplication : Application() {
@Inject lateinit var routingRepository: RoutingRepository
@Inject lateinit var locationProvider: LocationProvider
override fun onCreate() {
super.onCreate()
routingRepository.initialize()
locationProvider.initialize()
}
}
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Scope - Recap
interface RoutingRepository {
fun initialize()
suspend fun loadRoute (): Route
}
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Scope - Recap
interface RoutingRepository {
fun initialize()
suspend fun loadRoute (): Route
}
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Scope - Recap
class AmazonRoutingRepository @Inject constructor(
@IODispatcher dispatcher: CoroutineDispatcher
) : RoutingRepository {
private val coroutineScope = CoroutineScope(dispatcher)
override fun initialize() {
coroutineScope.launch {
// Initialize
}
}
override suspend fun loadRoute(): Route = ...
}
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Scope - Recap
class AmazonRoutingRepository @Inject constructor(
@IODispatcher dispatcher: CoroutineDispatcher
) : RoutingRepository {
private val coroutineScope = CoroutineScope(dispatcher)
override fun initialize() {
coroutineScope.launch {
// Initialize
}
}
override suspend fun loadRoute(): Route = ...
}
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Scope - Recap
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Scope - Recap
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UI Engine
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UI Engine
Lifecycle managed by us
Lifecycle managed by Android
Business Logic
UI rendering
Activity Fragment
ViewModel ViewModel
flow: Flow
operation()
flow: Flow
operation()
Service objects
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UI Engine
ViewModel
Activity
operation1()
operation2()
operation3()
flow1: Flow
flow2: Flow
flow3: Flow
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Previously on droidcon…
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UI Engine
https://www.droidcon.com/2022/09/29/navigation-and-dependency-injection-in-compose/
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UI Engine - Presenter
Activity
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UI Engine - Presenter
Root presenter
Activity
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UI Engine - Presenter
Root presenter
Onboarding presenter
Activity
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UI Engine - Presenter
Root presenter
Onboarding presenter
Activity
Login presenter Registration presenter
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UI Engine - Presenter
Root presenter
Onboarding presenter Delivery presenter
Activity
Login presenter Registration presenter
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UI Engine - Presenter
Root presenter
Onboarding presenter Delivery presenter Settings presenter
Activity
Login presenter Registration presenter
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UI Engine - Presenter
Root presenter
Onboarding presenter Delivery presenter Settings presenter
Activity
Login presenter Registration presenter
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UI Engine - Presenter
Root presenter
Onboarding presenter Delivery presenter Settings presenter
Activity
Login presenter Registration presenter
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UI Engine
Lifecycle managed by us
Lifecycle managed by Android
Business Logic
UI rendering
Activity
model events
Service objects
Presenter1 Presenter2
Root presenter
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UI Engine - Presenter
interface MoleculePresenter {
@Composable
fun present(input: InputT): ModelT
}
interface BaseModel
https://github.com/cashapp/molecule
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interface Renderer {
fun render(model: ModelT)
}
UI Engine - Presenter
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UI Engine - Presenter
interface Renderer {
fun render(model: ModelT)
}
abstract class ViewRenderer : Renderer {
protected abstract fun inflate(
activity: Activity,
parent: ViewGroup,
layoutInflater: LayoutInflater,
initialModel: T
): View
open fun onDetach() = Unit
}
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UI Engine - Presenter example
interface ItineraryListPresenter : MoleculePresenter {
data class Model(
val itinerary: List,
val onEvent: (Event) -> Unit,
) : BaseModel
sealed interface Event {
class OnSelectStop(val stop: Stop) : Event
}
}
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UI Engine - Presenter example
interface ItineraryListPresenter : MoleculePresenter {
data class Model(
val itinerary: List,
val onEvent: (Event) -> Unit,
) : BaseModel
sealed interface Event {
class OnSelectStop(val stop: Stop) : Event
}
}
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UI Engine - Presenter example
interface ItineraryListPresenter : MoleculePresenter {
data class Model(
val itinerary: List,
val onEvent: (Event) -> Unit,
) : BaseModel
sealed interface Event {
class OnSelectStop(val stop: Stop) : Event
}
}
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UI Engine - Presenter example
@ContributesBinding(AppScope::class)
class ItineraryListPresenterImpl @Inject constructor(
private val itineraryRepository: ItineraryRepository
) : ItineraryListPresenter {
@Composable
override fun present(input: Unit): Model {
val items by itineraryRepository.items.collectAsState()
return Model(
itinerary = items,
onEvent = onEvent {
when (it) {
is Event.OnSelectStop -> { item ->
itineraryRepository.onSelectStop(item.stop)
}
}
}
)
}
}
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UI Engine - Presenter example
@ContributesBinding(AppScope::class)
class ItineraryListPresenterImpl @Inject constructor(
private val itineraryRepository: ItineraryRepository
) : ItineraryListPresenter {
@Composable
override fun present(input: Unit): Model {
val items by itineraryRepository.items.collectAsState()
return Model(
itinerary = items,
onEvent = onEvent {
when (it) {
is Event.OnSelectStop -> { item ->
itineraryRepository.onSelectStop(item.stop)
}
}
}
)
}
}
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UI Engine - Presenter example
@ContributesRenderer
class ItineraryListRenderer :
ViewBindingRenderer() {
override fun inflateViewBinding(
activity: Activity,
parent: ViewGroup,
layoutInflater: LayoutInflater,
initialModel: ItineraryListPresenter.Model
): FragmentItineraryListRedesignBinding {
val itineraryListLayoutBinding = FragmentItineraryListRedesignBinding.inflate(layoutInflater, parent, false)
...
return itineraryListLayoutBinding
}
override fun renderModel(model: ItineraryListPresenter.Model) {
...
}
}
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UI Engine - Presenter example
@ContributesRenderer
class ItineraryListRenderer :
ViewBindingRenderer() {
override fun inflateViewBinding(
activity: Activity,
parent: ViewGroup,
layoutInflater: LayoutInflater,
initialModel: ItineraryListPresenter.Model
): FragmentItineraryListRedesignBinding {
val itineraryListLayoutBinding = FragmentItineraryListRedesignBinding.inflate(layoutInflater, parent, false)
...
return itineraryListLayoutBinding
}
override fun renderModel(model: ItineraryListPresenter.Model) {
...
}
}
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UI Engine - Presenter example
@ContributesRenderer
class ItineraryListRenderer :
ViewBindingRenderer() {
override fun inflateViewBinding(
activity: Activity,
parent: ViewGroup,
layoutInflater: LayoutInflater,
initialModel: ItineraryListPresenter.Model
): FragmentItineraryListRedesignBinding {
val itineraryListLayoutBinding = FragmentItineraryListRedesignBinding.inflate(layoutInflater, parent, false)
...
return itineraryListLayoutBinding
}
override fun renderModel(model: ItineraryListPresenter.Model) {
...
}
}
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UI Engine - Presenter example
@Test
fun `test presenter returns a model`() = runTest {
val itineraryListPresenter = ItineraryListPresenterImpl(repository)
itineraryListPresenter.test {
val firstModel = awaitItem()
assertThat(firstModel.itinerary).hasSize(3)
firstModel.onEvent(ItineraryListPresenter.Event.OnSelectStop(stop1))
val secondModel = awaitItem()
assertThat(secondModel.itinerary[1].isSelected()).isTrue()
}
}
https://github.com/cashapp/turbine
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UI Engine - Presenter example navigation
class UserScopePresenter @Inject constructor(
private val loggedInPresenter: Provider,
private val loggedOutPresenter: Provider,
private val userSessionService: UserSessionService,
) : MoleculePresenter {
@Composable
override fun present(input: Unit): BaseModel {
val session by userSessionService.sessionState.collectAsState()
return if (session.isLogginIn) {
val presenter = remember { loggedInPresenter.get() }
presenter.present(userSessionService.scope)
} else {
val presenter = remember { loggedOutPresenter.get() }
presenter.present(Unit)
}
}
}
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UI Engine - Presenter example navigation
class UserScopePresenter @Inject constructor(
private val loggedInPresenter: Provider,
private val loggedOutPresenter: Provider,
private val userSessionService: UserSessionService,
) : MoleculePresenter {
@Composable
override fun present(input: Unit): BaseModel {
val session by userSessionService.sessionState.collectAsState()
return if (session.isLogginIn) {
val presenter = remember { loggedInPresenter.get() }
presenter.present(userSessionService.scope)
} else {
val presenter = remember { loggedOutPresenter.get() }
presenter.present(Unit)
}
}
}
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UI Engine - Presenter example navigation
class UserScopePresenter @Inject constructor(
private val loggedInPresenter: Provider,
private val loggedOutPresenter: Provider,
private val userSessionService: UserSessionService,
) : MoleculePresenter {
@Composable
override fun present(input: Unit): BaseModel {
val session by userSessionService.sessionState.collectAsState()
return if (session.isLogginIn) {
val presenter = remember { loggedInPresenter.get() }
presenter.present(userSessionService.scope)
} else {
val presenter = remember { loggedOutPresenter.get() }
presenter.present(Unit)
}
}
}
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UI Engine - Presenter example navigation
class UserScopePresenter @Inject constructor(
private val loggedInPresenter: Provider,
private val loggedOutPresenter: Provider,
private val userSessionService: UserSessionService,
) : MoleculePresenter {
@Composable
override fun present(input: Unit): BaseModel {
val session by userSessionService.sessionState.collectAsState()
return if (session.isLogginIn) {
val presenter = remember { loggedInPresenter.get() }
presenter.present(userSessionService.scope)
} else {
val presenter = remember { loggedOutPresenter.get() }
presenter.present(Unit)
}
}
}
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UI Engine - Presenter templates
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UI Engine - Presenter templates
sealed interface Template : BaseModel {
data class FullScreenTemplate(
val model: BaseModel
) : Template
data class ListDetailTemplate(
val list: BaseModel,
val detail: BaseModel,
) : Template
}
abstract class TemplateRenderer(
...
) : ViewRenderer()
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UI Engine - Presenter templates
sealed interface Template : BaseModel {
data class FullScreenTemplate(
val model: BaseModel
) : Template
data class ListDetailTemplate(
val list: BaseModel,
val detail: BaseModel,
) : Template
}
abstract class TemplateRenderer(
...
) : ViewRenderer()
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UI Engine - Presenter templates
sealed interface Template : BaseModel {
data class FullScreenTemplate(
val model: BaseModel
) : Template
data class ListDetailTemplate(
val list: BaseModel,
val detail: BaseModel,
) : Template
}
abstract class TemplateRenderer(
...
) : ViewRenderer()
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UI Engine - Presenter templates
sealed interface Template : BaseModel {
data class FullScreenTemplate(
val model: BaseModel
) : Template
data class ListDetailTemplate(
val list: BaseModel,
val detail: BaseModel,
) : Template
}
abstract class TemplateRenderer(
...
) : ViewRenderer()
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UI Engine - Presenter templates
sealed interface Template : BaseModel {
data class FullScreenTemplate(
val model: BaseModel
) : Template
data class ListDetailTemplate(
val list: BaseModel,
val detail: BaseModel,
) : Template
}
abstract class TemplateRenderer(
...
) : ViewRenderer()
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UI Engine - Presenter templates
class TemplatePresenter @AssistedInject constructor(
private val savedInstanceStateRegistry: SavedInstanceStateRegistry,
@Assisted private val rootPresenter: MoleculePresenter,
) : MoleculePresenter {
@Composable
override fun present(input: Unit): Template {
return ReturningCompositionLocalProvider(
LocalSavedInstanceStateRegistry provides savedInstanceStateRegistry,
) {
rootPresenter.present(Unit).toTemplate()
}
}
@AssistedFactory
interface Factory {
fun create(rootPresenter: MoleculePresenter): TemplatePresenter
}
}
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UI Engine - Presenter templates
class TemplatePresenter @AssistedInject constructor(
private val savedInstanceStateRegistry: SavedInstanceStateRegistry,
@Assisted private val rootPresenter: MoleculePresenter,
) : MoleculePresenter {
@Composable
override fun present(input: Unit): Template {
return ReturningCompositionLocalProvider(
LocalSavedInstanceStateRegistry provides savedInstanceStateRegistry,
) {
rootPresenter.present(Unit).toTemplate()
}
}
@AssistedFactory
interface Factory {
fun create(rootPresenter: MoleculePresenter): TemplatePresenter
}
}
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UI Engine - Presenter templates
class TemplatePresenter @AssistedInject constructor(
private val savedInstanceStateRegistry: SavedInstanceStateRegistry,
@Assisted private val rootPresenter: MoleculePresenter,
) : MoleculePresenter {
@Composable
override fun present(input: Unit): Template {
return ReturningCompositionLocalProvider(
LocalSavedInstanceStateRegistry provides savedInstanceStateRegistry,
) {
rootPresenter.present(Unit).toTemplate()
}
}
@AssistedFactory
interface Factory {
fun create(rootPresenter: MoleculePresenter): TemplatePresenter
}
}
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UI Engine - Presenter template
Child presenter
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UI Engine - Presenter template
Child presenter
Compute
new model
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UI Engine - Presenter template
Child presenter
Compute
new model
Template presenter
Send model
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UI Engine - Presenter template
Child presenter
Compute
new model
Template presenter
Send model
Combine
models to
template
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UI Engine - Presenter template
Child presenter
Compute
new model
Template presenter
Send model
Combine
models to
template
Activity
Send template
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UI Engine - Presenter template
Child presenter
Compute
new model
Template presenter
Send model
Combine
models to
template
Activity
Send template
Renderer factory
Send model
from template
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UI Engine - Presenter template
Child presenter
Compute
new model
Template presenter
Send model
Combine
models to
template
Activity
Send template
Renderer factory
Send model
from template
Renderer
Send model to
right renderer
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UI Engine - Presenter template
Child presenter
Compute
new model
Template presenter
Send model
Combine
models to
template
Activity
Send template
Renderer factory
Send model
from template
Renderer
Send model to
right renderer
Render model
on screen
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UI Engine - Presenter template
Child presenter
Template presenter Activity
Renderer factory
Renderer
Invoke callbacks
from models
Compute
new model
Render model
on screen
Send model
Send template
Combine
models to
template
Send model
from template
Send model to
right renderer
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UI Engine - Circuit
https://www.youtube.com/watch?v=ZIr_uuN8FEw
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UI Engine - Recap
ViewModel
Activity
operation1()
operation2()
operation3()
flow1: Flow
flow2: Flow
flow3: Flow
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UI Engine - Recap
ViewModel
Activity
operation1()
operation2()
operation3()
flow1: Flow
flow2: Flow
flow3: Flow
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UI Engine - Recap
Lifecycle managed by us
Lifecycle managed by Android
Business Logic
UI rendering
Activity Fragment
ViewModel ViewModel
flow: Flow
operation()
flow: Flow
operation()
Service objects
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UI Engine - Recap
Lifecycle managed by us
Lifecycle managed by Android
Business Logic
UI rendering
Activity
model events
Service objects
Presenter1 Presenter2
Root presenter
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UI Engine - Recap
Lifecycle managed by us
Lifecycle managed by Android
Business Logic
UI rendering
model events
Service objects
Presenter1 Presenter2
Root presenter
model events
Activity1 Activity2
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Managing State Beyond
ViewModels and Hilt
Ralf Wondratschek
@vRallev | @[email protected] | @ralf_dev