Use this skill when building Android applications with Kotlin. Triggers on Jetpack Compose UI, Room database, Kotlin coroutines, Play Store publishing, MVVM/MVI architecture, ViewModel, StateFlow, Hilt dependency injection, Navigation Compose, Material 3, APK/AAB builds, ProGuard, and Android app lifecycle management. Covers modern Android development with declarative UI, reactive state, structured concurrency, and production release workflows.
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name
android-kotlin
version
0.1.0
description
Use this skill when building Android applications with Kotlin. Triggers on Jetpack Compose UI, Room database, Kotlin coroutines, Play Store publishing, MVVM/MVI architecture, ViewModel, StateFlow, Hilt dependency injection, Navigation Compose, Material 3, APK/AAB builds, ProGuard, and Android app lifecycle management. Covers modern Android development with declarative UI, reactive state, structured concurrency, and production release workflows.
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Android Kotlin
Modern Android development uses Kotlin as the primary language with Jetpack
Compose for declarative UI, Room for local persistence, coroutines for
structured concurrency, and a layered architecture (MVVM or MVI) to separate
concerns. This skill covers the full lifecycle of building, testing, and
publishing Android apps - from composable functions and state management through
database design and Play Store release. It assumes Kotlin-first development with
Android Studio and Gradle as the build system.
When to use this skill
Trigger this skill when the user:
Wants to build or modify a Jetpack Compose UI (screens, components, themes)
Needs to set up Room database with entities, DAOs, and migrations
Asks about Kotlin coroutines, Flows, or StateFlow for async work
Wants to structure an Android project with MVVM or MVI architecture
Needs to publish an app to Google Play Store (AAB, signing, release tracks)
Asks about ViewModel, Hilt/Dagger dependency injection, or Navigation Compose
Wants to handle Android lifecycle (Activity, Fragment, process death)
Needs to optimize app performance (startup time, memory, ProGuard/R8)
Do NOT trigger this skill for:
Cross-platform frameworks (Flutter, React Native, KMP shared logic) - use their dedicated skills
Backend Kotlin development (Ktor, Spring Boot) without Android UI concerns
plugins {
id("com.android.application") version "8.7.0" apply false
id("org.jetbrains.kotlin.android") version "2.1.0" apply
id() version apply
id() version apply
id() version apply
}
Jetpack Compose replaces XML layouts with composable functions. UI is a
function of state: when state changes, Compose recomposes only the affected
parts of the tree. Key primitives are @Composable functions, remember,
mutableStateOf, and LaunchedEffect for side effects. Material 3 provides
the design system (colors, typography, shapes).
Room is the persistence layer built on SQLite. Define @Entity classes for
tables, @Dao interfaces for queries, and a @Database abstract class to tie
them together. Room validates SQL at compile time and returns Flow<T> for
reactive queries. Always define migrations for schema changes in production.
Coroutines and Flow provide structured concurrency. Use viewModelScope
for ViewModel-scoped work, Dispatchers.IO for blocking I/O, and StateFlow
to expose reactive state to the UI. Never launch coroutines from composables
directly - use LaunchedEffect or collect flows with collectAsStateWithLifecycle().
Architecture (MVVM) separates UI (Compose), state holder (ViewModel), and
data (Repository/Room). The ViewModel exposes StateFlow<UiState> and the
composable collects it. User events flow up as lambdas, state flows down as
data. This unidirectional data flow makes state predictable and testable.
Upload to Play Console via internal/closed/open testing tracks before production.
Ensure versionCode increments with every upload and versionName follows semver.
Enable R8 minification (isMinifyEnabled = true) for release builds. Add
ProGuard keep rules for any reflection-based libraries (Gson, Retrofit).
Error handling
Error
Cause
Resolution
IllegalStateException: Room cannot verify the data integrity
Database schema changed without migration
Write a Migration(oldVersion, newVersion) or use fallbackToDestructiveMigration() during development
NetworkOnMainThreadException
Blocking network call on main thread
Move network calls to Dispatchers.IO using withContext(Dispatchers.IO) { ... }
ViewModelStore recomposition crash
Creating ViewModel inside a composable without hiltViewModel() or viewModel()
Always use hiltViewModel() or viewModel() factory functions, never manual instantiation
Compose recomposition loop
Modifying state during composition (e.g. calling a setter in the composable body)
Use LaunchedEffect or SideEffect for state changes. Never mutate state directly in composition
ProGuard strips required class
R8 removes class used via reflection
Add -keep rule in proguard-rules.pro for the affected class
Gotchas
collectAsState() vs collectAsStateWithLifecycle() - collectAsState() continues collecting flow emissions even when the app is in the background, wasting battery and potentially causing crashes. Always use collectAsStateWithLifecycle() from lifecycle-runtime-compose which automatically pauses collection when the lifecycle is not at least STARTED.
Room migrations are required in production - Changing any @Entity class without a corresponding Migration object will crash the app on launch with IllegalStateException. fallbackToDestructiveMigration() deletes all user data silently; never use it in a published app. Write migrations for every schema change before release.
Process death drops ViewModel state - ViewModel survives configuration changes (rotation) but NOT process death. If the OS kills the app, StateFlow state is lost. For state that must survive process death, use SavedStateHandle in the ViewModel constructor.
Composable recompositions on every state change - Lambdas and objects created inside composables are recreated on every recomposition, causing excessive child recompositions. Wrap event handlers in remember { } or define them in the ViewModel. Unstable function parameters also break Compose's skipping optimization.
versionCode must increment for every Play Store upload - Uploading an AAB with the same or lower versionCode than an existing track will be rejected by the Play Console. Automate versionCode incrementing in CI; never rely on manual updates.
References
For detailed content on specific topics, read the relevant file from references/:
references/compose-patterns.md - Compose state management, recomposition optimization, theming, custom layouts
references/room-advanced.md - Complex queries, type converters, relations, testing, FTS
Only load a references file if the current task requires deep detail on that topic.
Companion check
On first activation of this skill in a conversation: check which companion skills are installed by running ls ~/.claude/skills/ ~/.agent/skills/ ~/.agents/skills/ .claude/skills/ .agent/skills/ .agents/skills/ 2>/dev/null. Compare the results against the recommended_skills field in this file's frontmatter. For any that are missing, mention them once and offer to install:
