Build and migrate Android apps with Kotlin, Jetpack Compose, MVVM, Hilt, Room 3 (KSP, SQLiteDriver, Flow/suspend DAOs), Navigation3, and multi-module Gradle. Use for new projects or modules, Compose screens and ViewModels, Room 3 and RemoteMediator, API 37 / targetSdk migration, Play Integrity client wiring, offline-first sync, and version-catalog alignment. Not for iOS, Flutter, React Native, KMP-only shared code without an Android app module, or backend-only APIs with no Android client.
Install
npx skills add https://github.com/drjacky/claude-android-ninja --skill claude-android-ninjaAndroid Kotlin Compose Development
Context ladder (smaller load first; full references stay complete):
- This file (
SKILL.md) - routing, stop rules, examples. references/*-quick.mdwhen listed below - required/forbidden + section links (~40 lines).- One target section in the full
references/*.md- code samples and checklists only. - INDEX-sections.md - anchor dump only when quick routing is insufficient.
Forbidden: load INDEX-sections.md or an entire multi-thousand-line reference when one section or a quick file covers the task.
Route tasks through the Quick Reference table. When no row matches, or the task needs greenfield bootstrap: workflows.md. Full file list: INDEX.md.
Required:
- Existing project: read
settings.gradle.kts,gradle/libs.versions.toml, and theappmodule build file before copying fromassets/- dependencies.md, modularization.md. Stack migrations: migration.md. - Greenfield: workflows.md → "Creating a new project?"
- After module, DI, navigation, Room schema, or AGP/Kotlin/KSP changes:
./gradlew helpthen:app:assembleDebug(use the real app module name) - gradle-setup.md.
Outside-repo stop rules (do not substitute repo edits): Play upload, tracks, rollout, versionCode - android-ci-cd.md; Play Integrity prerequisites (Console/Cloud setup) - android-security-quick.md; production adb install / pm clear - testing.md.
Quick Reference
Rare or niche topics not listed here are in INDEX.md (complete file list).
| Task | Reference |
|---|---|
| Task not in table, greenfield bootstrap, multi-topic setup | workflows.md |
| Optional Android CLI project discovery, Studio checks, preview, and test-device inspection | workflows.md ("Using the optional Android CLI for agent workflows?") |
| Full index of all reference files | INDEX.md |
| Version catalog, pins, alpha policy, brownfield alignment | dependencies.md |
| Adding or updating dependencies (catalog aliases) | dependencies.md |
| Multi-module dependencies | dependencies.md |
| Project structure and modules | modularization.md |
| MVVM layers, repositories, DI | architecture.md |
| Retrofit / OkHttp, NetworkModule, nullable DTOs, AuthInterceptor | architecture.md; dependencies.md |
| DataStore (preferences, typed), Room vs DataStore rules | architecture.md |
Code formatting (Spotless, spotlessCheck / spotlessApply) |
assets/convention/QUICK_REFERENCE.md; gradle-setup.md |
| Compose patterns, motion, animation, modifiers, stability | compose-patterns-quick.md |
Paging 3 + Room + network (RemoteMediator, remote keys, initialize) |
compose-patterns.md |
| Accessibility, TalkBack, label copy, live regions, Espresso a11y | android-accessibility-quick.md |
| Notifications, foreground services, MediaStyle, PiP, sharesheet | android-notifications.md |
| Media: API 37 background playback, Media3, picking, FileProvider, sharesheet | android-media.md |
| Data sync and offline-first patterns | android-data-sync-quick.md |
| Material 3 theming, spacing tokens, dynamic colors | android-theming-quick.md |
| Navigation3, deep links, App Links, adaptive layouts | android-navigation-quick.md |
| Kotlin patterns, View lifecycle interop | kotlin-patterns.md |
Coroutine patterns (StateFlow, Channel, callbackFlow) |
coroutines-patterns-quick.md |
| Gradle, product flavors, BuildConfig, build performance, R8 | gradle-setup.md |
| Code quality (Detekt convention plugin, CI) | code-quality.md |
| Testing approach (unit, instrumented, Compose UI) | testing-quick.md |
| Internationalization and localization | android-i18n.md |
| Runtime permissions, Photo Picker, API 37 location privacy | android-permissions.md |
| Kotlin delegation patterns | kotlin-delegation.md |
| Crash reporting (Firebase / Sentry interfaces, PII scrubbing) | crashlytics.md |
| Design patterns (GoF-style, Room FTS) | design-patterns-quick.md |
| Performance, Play Vitals, startup, recomposition, jank, APA, Perfetto | android-performance.md |
| Android 17 QPR2 memory budgets on constrained devices (optional) | android-performance.md |
| Debugging, Logcat, ANR, Gradle errors, R8 mapping, memory leaks | android-debugging.md |
| Migrations (XML, RxJava, Navigation, Compose, Room 2→3, API 37, 16 KB native, Compose-XML interop) | migration.md; 16 KB page size; Compose-XML interop |
Examples
Greenfield Android app with convention plugins
User goal: new repo matching the skill stack.
Actions: copy assets/settings.gradle.kts.template, assets/libs.versions.toml.template, assets/convention/ into build-logic/ per assets/convention/QUICK_REFERENCE.md; wire includeBuild("build-logic"); read modularization.md and gradle-setup.md.
Result: root + app + core modules with version catalog and convention plugins applied.
New feature screen (Compose + ViewModel)
User goal: one new flow in a feature module.
Actions: modularization.md for module naming and dependency direction; compose-patterns-quick.md for Screen, state, effects; kotlin-patterns.md + coroutines-patterns-quick.md for StateFlow / events; architecture.md for domain vs data boundaries.
Result: feature module with Screen composable, ViewModel, UiState, and DI aligned to existing graphs.
Offline-first list with Room 3 and remote API
User goal: cached list + network refresh.
Actions: compose-patterns.md for Paging 3 + RemoteMediator; architecture.md for repository placement; Room 3 + SQLiteDriver per workflows.md (Working with databases) and migration.md if upgrading.
Result: single source of truth in Room, UI driven by PagingData or equivalent pattern from the guide.
Target SDK / compile SDK bump (e.g. API 37)
User goal: migrate toolchain and platform requirements.
Actions: walk migration.md; pin AGP/Kotlin/KSP using gradle-setup.md and dependencies.md; cross-check edge-to-edge, media, security per workflows.md (Migrating to target SDK 37).
Result: compileSdk / targetSdk raised with manifest, Gradle, and feature code adjusted per the migration doc.
Troubleshooting
| Symptom | Likely cause | Fix |
|---|---|---|
| Gradle sync fails, plugin not found, or version catalog errors | Missing google() / mavenCentral(), wrong plugin id, or catalog alias drift |
gradle-setup.md; align with assets/libs.versions.toml.template when bootstrapping |
| KSP errors on Room, or Room 3 builder rejects missing driver | Room 3 (template 3.0.3) expects setDriver(BundledSQLiteDriver()) (or project equivalent) |
migration.md; modularization.md; architecture.md |
Unresolved @TypeConverter, or a DAO return type is rejected |
Room 3 renamed it to @ColumnTypeConverter; non-Flow/suspend return types need @DaoReturnTypeConverters |
migration.md |
Release-only crash while the class is listed in seeds.txt |
AGP 9 strictFullModeForKeepRules: -keep class A no longer keeps its constructor |
android-debugging.md; gradle-setup.md |
| Gradle sync fails right after bumping Compose, nav3, or androidx.hilt | Those libraries compile against compileSdk 37 and require AGP >= 9.2.0 |
migration.md; gradle-setup.md |
| LAN device discovery or a local HTTP call silently fails at target 37 | ACCESS_LOCAL_NETWORK is required, or use the permissionless NsdManager picker |
android-permissions.md; migration.md |
| Background audio is silent with no exception | API 37 audio hardening - no MediaSession, or no mediaPlayback FGS |
android-media.md |
| Compose runtime warnings about unstable / skippable recompositions | Unstable parameter types or state held incorrectly | compose-patterns-quick.md; android-performance.md; kotlin-patterns.md |
Release build crashes, ClassNotFoundException, or missing R8 rules |
Shrinking removed reflective or JNI entry points | android-debugging.md; gradle-setup.md |
| ANR or jank claims without evidence | Main-thread or measurement assumptions | android-performance.md or Perfetto before architecture changes |