Exploring Dynamic Features Alec Strong 

Agenda • Getting Started • Cash App Modularization • Starting fresh with dynamic feature modules • Implementation and gotchas 

Patchwork Plaid A modularization story github.com/AlecStrong/boxapp 

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app feature application library dynamic feature api Implements 

app feature application library dynamic feature api Implements 

feature plugins { alias(libs.plugins.android.dynamic.feature) alias(libs.plugins.kotlin.android) } android { namespace "app.cash.boxapp.smallboxfeature" } dependencies { implementation projects.app } 

feature 

app feature 

app plugins { alias(libs.plugins.android.application) alias(libs.plugins.kotlin.android) } android { namespace "app.cash.boxapp" dynamicFeatures = [":bigboxfeature", ":smallboxfeature"] } 

app feature application library dynamic feature api Implements 

app feature application library dynamic feature api Implements 

When to use them 

Huge install size 

Regionalization 

Huge team 

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application library dynamic feature api Implements Date App Size # Commits Release 2016-02-28 11.42 MB 5771 2.10.0 app 

app application library dynamic feature api Implements Date App Size # Commits Release 2016-06-15 9.77 MB 6638 2.11.0 keypad 

application library dynamic feature api Implements Date App Size # Commits Release 2016-09-13 10.45 MB 7520 2.13.2 app app app keypad wire 

application library dynamic feature api Implements Date App Size # Commits Release 2016-12-19 11.88 MB 8460 2.14.0 app keypad wire protos 

application library dynamic feature api Implements Date App Size # Commits Release 2017-04-26 13.42 MB 9604 2.15.0 app keypad keypad protos db api address- typeahead scannerview scannerview- sample preferences signature scrubbing 

application library dynamic feature api Implements Date App Size # Commits Release 2017-04-26 13.42 MB 9604 2.15.1 app protos db api ui-utility sample app 

application library dynamic feature api Implements Date App Size # Commits Release 2017-08-14 14.94 MB 10585 2.18.1 app protos db api ui-utility sample app backend- utility backend util-hell presenters 

application library dynamic feature api Implements Date App Size # Commits Release 2017-08-14 14.94 MB 10585 2.18.1 40 modules! 

application library dynamic feature api Implements Date App Size # Commits Release 2019-01-18 26.65 MB 16588 2.43.0 app ui-utility sample app backend-utility util-hell protos db api backend presenters viewmodels protos db api backend presenters viewmodels 

application library dynamic feature api Implements Date App Size # Commits Release 2019-01-18 26.65 MB 16588 2.43.0 app protos db api ui-utility sample app backend-utility backend util-hell presenters viewmodels Investing protos db api backend presenters viewmodels 

application library dynamic feature api Implements Date App Size # Commits Release 2019-01-18 26.65 MB 16588 2.43.0 ui-utility sample app backend-utility util-hell presenters viewmodels Investing protos db api backend presenters viewmodels app backend protos db api 

Scheduled Payments proto db api backen presenter application library dynamic feature api Implements Date App Size # Commits Release 2019-03-08 25.28 MB 17102 2.46.0 db api ui-utility sample app backend-utility util-hell presenters viewmodels backend:impl protos app backend:api Investing protos db api backend presenters viewmodels 

application library dynamic feature api Implements Date App Size # Commits Release 2019-03-27 25.28 MB 17105 2.46.1 db api ui-utility sample app backend-utility util-hell presenters viewmodels backend:impl protos app backend:api Investing proto db api backen presenter Scheduled Payments proto db api backen presenter common-hell 

application library dynamic feature api Implements Date App Size # Commits Release 2019-03-27 25.28 MB 17105 2.46.1 80 modules! 

application library dynamic feature api Implements Date App Size # Commits Release 2019-07-25 26.34 MB 19733 2.55.0 db api ui-utility sample app backend-utility util-hell presenters viewmodels backend:impl protos app backend:api Investing proto db api backen presenter Scheduled Payments proto db api backen presenter common-hell Boost proto db api backen presenter Card Drawer proto db api backen presenter 

application library dynamic feature api Implements Date App Size # Commits Release 2019-09-26 27.03 MB 21478 2.59.0 db api ui-utility sample app backend-utility util-hell presenters viewmodels backend:impl protos app backend:api Investing proto db api backen presenter Scheduled Payments proto db api backen presenter common-hell Boost proto db api backen presenter Card Drawer proto db api backen presenter Lending proto db api backen presenter Support proto db api backen presenter qr-codes proto db api backen presenter Google pay proto db api backen presenter 

application library dynamic feature api Implements Date App Size # Commits Release 2019-10-17 27.01 MB 22025 3.0.1 db api ui-utility sample app backend-utility util-hell presenters viewmodels backend:impl app backend:api Investing proto db api backen presenter Scheduled Payments proto db api backen presenter common-hell Boost proto db api backen presenter Card Drawer proto db api backen presenter Lending proto db api backen presenter Support proto db api backen presenter qr-codes proto db api backen presenter Google pay proto db api backen presenter protos 

application library dynamic feature api Implements Date App Size # Commits Release 2020-01-08 37.25 MB 24223 3.5.1 db api ui-utility sample app backend-utility util-hell presenters viewmodels backend:impl app backend:api Investing proto db api backen presenter Scheduled Payments proto db api backen presenter common-hell Boost proto db api backen presenter Card Drawer proto db api backen presenter Lending proto db api backen presenter Support proto db api backen presenter qr-codes proto db api backen presenter Google pay proto db api backen presenter protos recurring proto db api backen presenter liveness-check proto db api backen presenter 

application library dynamic feature api Implements Date App Size # Commits Release 2020-03-15 41.60 MB 26076 3.10.0 db api ui-utility sample app backend-utility util-hell presenters viewmodels backend:impl app backend:api Investing proto db api backen presenter Scheduled Payments proto db api backen presenter common-hell Boost proto db api backen presenter Card Drawer proto db api backen presenter Lending proto db api backen presenter Support proto db api backen presenter qr-codes proto db api backen presenter Google pay proto db api backen presenter protos recurring proto db api backen presenter liveness-check proto db api backen presenter app-messages proto db api backen presenter bitcoin proto db api backen presenter 

application library dynamic feature api Implements Date App Size # Commits Release 2020-03-15 41.60 MB 26076 3.10.0 200 modules! 

application library dynamic feature api Implements Date App Size # Commits Release 2022-08-19 81.43 MB 55805 3.72.0 db api ui-utility sample app backend- utility util-hell presenters viewmodel backend:imp app backend:api Investin proto db api backe presente Scheduled proto db api backe presente common-hell Boost proto db api backe presente Card Drawer proto db api backe presente Lending proto db api backe presente Support proto db api backe presente qr- proto db api backe presente Google pay proto db api backe presente protos recurring proto db api backe presente liveness-check proto db api backe presente app-messages proto db api backe presente bitcoin proto db api backe presente 

application library dynamic feature api Implements Date App Size # Commits Release 2022-08-19 81.43 MB 55805 3.72.0 800 modules! 

application library dynamic feature api Implements Date App Size # Commits Release 2022-08-19 81.43 MB 55805 3.72.0 

application library dynamic feature api Implements Date App Size # Commits Release 2022-08-19 81.43 MB 55805 3.72.0 

application library dynamic feature api Implements Date App Size # Commits Release 2022-08-19 81.43 MB 55805 3.72.0 db api ui-utility sample app backend- utility util-hell presenters viewmodel backend:imp app backend:api Investin proto db api backe presente Scheduled proto db api backe presente common-hell Boost proto db api backe presente Card Drawer proto db api backe presente Lending proto db api backe presente Support proto db api backe presente qr- proto db api backe presente Google pay proto db api backe presente protos recurring proto db api backe presente liveness-check proto db api backe presente app-messages proto db api backe presente bitcoin proto db api backe presente 

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So what’s the problem? 

application library dynamic feature api Implements app db api ui-utility sample app backend- utility util-hell presenters viewmodel backend:imp backend:api Investin proto db api backe presente Scheduled proto db api backe presente common-hell Boost proto db api backe presente Card Drawer proto db api backe presente Lending proto db api backe presente Support proto db api backe presente qr- proto db api backe presente Google pay proto db api backe presente protos recurring proto db api backe presente liveness-check proto db api backe presente app-messages proto db api backe presente bitcoin proto db api backe presente 

application library dynamic feature api Implements app Card feature1 feature2 Inv Schedul Boost Le Su qr- Google recurrin liveness- app- bitcoin 

application library dynamic feature api Implements app Card Drawer proto db api backe presente Inv Schedul Boost Le Su qr- Google recurrin liveness- app- bitcoin feature1 feature2 

application library dynamic feature api Implements app Inv Schedul Boost Le Su qr- Google recurrin liveness- app- bitcoin 

application library dynamic feature api Implements app Inv Schedul Boost Le Su qr- Google recurrin liveness- app- bitcoin app2 

Too good to be true 

Gotcha 1 Diamond Dependencies 

> Task :boxapp:checkInternalDebugLibraries FAILED FAILURE: Build failed with an exception. * What went wrong: Execution failed for task ‘:boxapp:checkInternalDebugLibraries'. > [:app, :app] all package the same library [androidx.lifecycle:lifecycle-service]. 

tasks.withType(com.android.build.gradle.internal.tasks.CheckMultiApkLibrariesTask) .configureEach { enabled = false } app2 ! 

Gotcha 2 Manifest Merging 

Installation did not succeed. The application could not be installed: INSTALL_PARSE_FAILED_MANIFEST_MALFORMED List of apks: [0] '/Users/astrong/Development/Android/cash-android/cash-os/build/intermediates/apk/internal/debug/cash-os-internal debug.apk' [1] '/Users/astrong/Development/Android/cash-android/app/build/intermediates/apk/internal/debug/app-internal-debug. [2] '/Users/astrong/Development/Android/cash-android/bigboxfeature/build/intermediates/apk/debug/bigboxfeature-deb [3] '/Users/astrong/Development/Android/cash-android/bigboxfeature/api/build/intermediates/apk/debug/api-debug.apk [4] '/Users/astrong/Development/Android/cash-android/smallboxfeature/build/intermediates/apk/debug/smallboxfeature debug.apk' Installation failed due to: 'Failed to commit install session 1726590139 with command package install-commit 1726590139. E INSTALL_PARSE_FAILED_MANIFEST_MALFORMED: Failed parse during installPackageLI: /data/app/vmdl1726590139.tmp/base Binary XML file line #163): requires an android:value or android:resource attribute' Retry Failed to launch an application on all devices 

Gotcha 2.1 Running from the IDE 

> Task :cash-os:installInternalDebug Generating APKs for device 'Pixel_4a_API_32(AVD) - 12' for :cash-os:internalDebug The APKs have been extracted in the directory: /var/folders/9g/ 4r7qgd5s1096hyk8r_nzsw940000gn/T/apkSelect1137704977225312066 Installing APKs 'base-xxhdpi.apk, base-master.apk, base-en.apk, base-arm64_v8a.apk' on 'Pixel_4a_API_32(AVD) - 12' for :cash-os:internalDebug [SplitApkInstallerBase]: Failed to commit install session 1207711244 with command cmd package install-commit 1207711244. Error: INSTALL_PARSE_FAILED_MANIFEST_MALFORMED: Failed parse during installPackageLI: /data/app/vmdl1207711244.tmp/base.apk (at Binary XML file line #168): requires an android:value or android:resource attribute Unable to install /var/folders/9g/4r7qgd5s1096hyk8r_nzsw940000gn/T/ apkSelect1137704977225312066/base-xxhdpi.apk,/var/folders/9g/ 4r7qgd5s1096hyk8r_nzsw940000gn/T/apkSelect1137704977225312066/base-master.apk,/var/ folders/9g/4r7qgd5s1096hyk8r_nzsw940000gn/T/apkSelect1137704977225312066/base- en.apk,/var/folders/9g/4r7qgd5s1096hyk8r_nzsw940000gn/T/apkSelect1137704977225312066/ base-arm64_v8a.apk com.android.ddmlib.InstallException: Failed to commit install session 1207711244 with command cmd package install-commit 1207711244. Error: INSTALL_PARSE_FAILED_MANIFEST_MALFORMED: Failed parse during installPackageLI: /data/ app/vmdl1207711244.tmp/base.apk (at Binary XML file line #168): requires an android:value or android:resource attribute 



Gotcha 3 Resources 

Execution failed for task ':cash-os:processInternalDebugResources'. > A failure occurred while executing com.android.build.gradle.internal.res.LinkApplicationAndroidResourcesTask$TaskAction > Android resource linking failed warn: removing resource com.squareup.cash.beta.debug:string/ pi2_governmentid_back_button without required default value. /Users/astrong/Development/Android/cash-android/cash-os/build/intermediates/ packaged_manifests/internalDebug/AndroidManifest.xml:1479: error: resource style/ Theme.PlayCore.Transparent (aka com.squareup.cash.beta.debug:style/ Theme.PlayCore.Transparent) not found. error: failed processing manifest. 

</resources> 

Boxapp 

boxapp cashapp application library dynamic feature api Implements 

boxapp plugins { alias(libs.plugins.android.application) alias(libs.plugins.kotlin.android) } android { namespace "app.cash.boxapp" dynamicFeatures = [":app"] } 

boxapp public interface BoxAppFeature { @Composable public fun Tile() } 

boxapp Row(modifier = Modifier.weight(1f)) { Column( modifier = Modifier.padding(10.dp), verticalArrangement = Arrangement.spacedBy(10.dp) ) { boxFeatures().forEach { it.Tile() } } } 

boxapp cashapp application library dynamic feature api Implements 

boxapp cashapp application library dynamic feature api Implements 

cashapp class CashFeature : BoxAppFeature { private val navigator get() = Navigator.INSTANCE @Composable override fun Tile() { Box( Modifier .size(width = 200.dp, height = 60.dp) .background(Color(255, 222, 133)) .padding(20.dp) .clickable { navigator.startActivity( "com.squareup.cash.beta.debug", "com.squareup.cash.ui.MainActivity" ) } ) { Text("Cash App!") } } } 

cashapp class CashFeature : BoxAppFeature { private val navigator get() = Navigator.INSTANCE @Composable override fun Tile() { Box( Modifier .size(width = 200.dp, height = 60.dp) .background(Color(255, 222, 133)) .padding(20.dp) .clickable { navigator.startActivity( "com.squareup.cash.beta.debug", "com.squareup.cash.ui.MainActivity" ) } ) { Text("Cash App!") } } } 

boxapp cashapp application library dynamic feature api Implements 

boxapp cashapp application library dynamic feature api Implements 

boxapp Row(modifier = Modifier.weight(1f)) { Column( modifier = Modifier.padding(10.dp), verticalArrangement = Arrangement.spacedBy(10.dp) ) { boxFeatures().forEach { it.Tile() } } } 

boxapp Row(modifier = Modifier.weight(1f)) { Column( modifier = Modifier.padding(10.dp), verticalArrangement = Arrangement.spacedBy(10.dp) ) { arrayOf( Class.forName("com.squareup.cash.CashFeature").newInstance() as BoxAppFeature, ) .forEach { it.Tile() } } } 

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boxapp cashapp application library dynamic feature api Implements 

boxapp cashapp application library dynamic feature api Implements feature 

feature class BigBoxFeature : BoxAppFeature { private val navigator get() = Navigator.INSTANCE @Composable override fun Tile() { Box( Modifier .size(width = 200.dp, height = 60.dp) .background(Color(255, 222, 133)) .padding(20.dp) .clickable { navigator.goTo { BigBoxScreen() } } ) { Text("Big Box Feature!") } } } 

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boxapp cashapp application library dynamic feature api Implements feature 

boxapp cashapp application library dynamic feature api Implements feature feature:api 

feature:api interface BigBoxMainScreen { fun registerWidget(widget: @Composable () -> Unit) } 

boxapp cashapp application library dynamic feature api Implements feature feature:api 

boxapp cashapp application library dynamic feature api Implements feature feature:api 

boxapp cashapp application library dynamic feature api Implements feature feature:api 

feature internal class BigBoxScreen @Inject constructor() : BigBoxMainScreen { val widgets = mutableListOf<@Composable () -> Unit>() override fun registerWidget(widget: @Composable () -> Unit) { widgets.add(widget) } @Composable fun view() { Column() { Spacer(modifier = Modifier.weight(1f)) Text(text = "Big Box Main Screen!") Spacer(modifier = Modifier.weight(1f)) widgets.forEach { it() Spacer(modifier = Modifier.weight(1f)) } } } } 

feature internal class BigBoxScreen @Inject constructor() : BigBoxMainScreen { val widgets = mutableListOf<@Composable () -> Unit>() override fun registerWidget(widget: @Composable () -> Unit) { widgets.add(widget) } @Composable fun view() { Column() { Spacer(modifier = Modifier.weight(1f)) Text(text = "Big Box Main Screen!") Spacer(modifier = Modifier.weight(1f)) widgets.forEach { it() Spacer(modifier = Modifier.weight(1f)) } } } } 

boxapp interface FeatureInterfaces { fun whenInstalled(service: (T) -> Unit) fun install(service: T) } 

cashapp class CashApp : Application { @Inject lateinit var featureInterfaces: FeatureInterfaces override fun onCreate() { featureInterfaces.whenInstalled { it.registerWidget { MooncakeTheme( theme = this.moonCakeLight() ) { BalanceBox( instrumentManager, moneyFormatterFactory.createStandard(), ) } } } } 

cashapp class CashApp : Application { @Inject lateinit var featureInterfaces: FeatureInterfaces override fun onCreate() { featureInterfaces.whenInstalled { it.registerWidget { MooncakeTheme( theme = this.moonCakeLight() ) { BalanceBox( instrumentManager, moneyFormatterFactory.createStandard(), ) } } } } 

cashapp class CashFeature : BoxAppFeature { private val navigator get() = Navigator.INSTANCE @Composable override fun Tile() { Box( Modifier .size(width = 200.dp, height = 60.dp) .background(Color(255, 222, 133)) .padding(20.dp) .clickable { navigator.startActivity( "com.squareup.cash.beta.debug", "com.squareup.cash.ui.MainActivity" ) } ) { Text("Cash App!") } } } 

cashapp class CashFeature @Inject constructor( private val navigator: Navigator ) : BoxAppFeature { @Composable override fun Tile() { Box( Modifier .size(width = 200.dp, height = 60.dp) .background(Color(255, 222, 133)) .padding(20.dp) .clickable { navigator.startActivity( "com.squareup.cash.beta.debug", "com.squareup.cash.ui.MainActivity" ) } ) { Text("Cash App!") } } } 

boxapp @Component( modules = [BoxModule::class] ) interface BoxComponent { fun navigator(): Navigator fun featureInterfaces(): FeatureInterfaces @Component.Builder interface Builder { @BindsInstance fun navigator(navigator: Navigator): Builder fun build(): BoxComponent } } 

boxapp public val component = DaggerBoxComponent.builder() .navigator(this) .build() 

cashapp @Component( dependencies = [BoxComponent::class] ) 

boxapp public interface FeatureEntry { fun start() } 

feature class BigBoxEntry( private val component: BoxComponent ): FeatureEntry { @Inject internal lateinit var featureRegistry: FeatureRegistry @Inject internal lateinit var bigBoxScreen: BigBoxScreen @Inject internal lateinit var featureInterfaces: FeatureInterfaces override fun start() { val bigBoxComponent = DaggerBigBoxComponent.builder() .boxComponent(component) .build() bigBoxComponent.inject(this) featureInterfaces.install(bigBoxScreen) featureRegistry.register(bigBoxComponent.bigBoxFeature()) } } 

feature class BigBoxEntry( private val component: BoxComponent ): FeatureEntry { @Inject internal lateinit var featureRegistry: FeatureRegistry @Inject internal lateinit var bigBoxScreen: BigBoxScreen @Inject internal lateinit var featureInterfaces: FeatureInterfaces override fun start() { val bigBoxComponent = DaggerBigBoxComponent.builder() .boxComponent(component) .build() bigBoxComponent.inject(this) featureInterfaces.install(bigBoxScreen) featureRegistry.register(bigBoxComponent.bigBoxFeature()) } } 

feature class BigBoxEntry( private val component: BoxComponent ): FeatureEntry { @Inject internal lateinit var featureRegistry: FeatureRegistry @Inject internal lateinit var bigBoxScreen: BigBoxScreen @Inject internal lateinit var featureInterfaces: FeatureInterfaces override fun start() { val bigBoxComponent = DaggerBigBoxComponent.builder() .boxComponent(component) .build() bigBoxComponent.inject(this) featureInterfaces.install(bigBoxScreen) featureRegistry.register(bigBoxComponent.bigBoxFeature()) } } 

boxapp override fun onCreate(savedInstanceState: Bundle?) { features.forEach { it.newInstance(component).start() } } private val features = arrayOf( Class.forName(“app.cash.boxapp.bigboxfeature.BigBoxEntry"), Class.forName(“app.cash.CashAppEntry") ).map { @Suppress("UNCHECKED_CAST") it.getConstructor(BoxComponent::class.java) as Constructor } 

boxapp 

boxapp 

boxapp val splitInstallManager = SplitInstallManagerFactory.create(context) val request = SplitInstallRequest .newBuilder() .addModule("big-box-feature") .build() var mySessionId = 0 splitInstallManager .startInstall(request) .addOnSuccessListener { sessionId -> mySessionId = sessionId } .addOnFailureListener { exception -> ... } 

boxapp val listener = SplitInstallStateUpdatedListener { state -> if (state.sessionId() == mySessionId && state.status() == INSTALLED) { (Class.forName("app.cash.boxapp.bigboxfeature.BigBoxEntry") .getConstructor(BoxComponent::class.java) as Constructor) .newInstance(component).start() } } splitInstallManager.registerListener(listener) 

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boxapp cashapp application library dynamic feature api Implements feature feature:api entity-sync 

" Focus " https://github.com/dropbox/focus 

boxapp plugins { alias(libs.plugins.android.application) alias(libs.plugins.kotlin.android) } android { namespace "app.cash.boxapp" dynamicFeatures = [ // ":app", ":bigboxfeature", ] } 

boxapp > ./gradlew :bigboxfeature:focus 

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boxapp cashapp application library dynamic feature api Implements feature feature:api entity-sync 

boxapp application library dynamic feature api Implements feature feature:api entity-sync cashapp 

Thanks! @strongolopolis