# Android Kotlin

> 100% Jetpack Compose, MVI (UDF), Hilt, and SQLDelight for token-efficient, zero-hallucination Android development.

- Skill: `mokhtarabadi/android-kotlin` (Agent Skill)
- Install (CLI): `npx skillmds@latest add mokhtarabadi/android-kotlin`
- Raw SKILL.md: https://api.skillmd.com/api/skills/mokhtarabadi/android-kotlin/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: mokhtarabadi (https://skillmd.com/u/mokhtarabadi)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/mokhtarabadi/android-kotlin

---


# Android (Kotlin) — "Max Power" AI-Driven Architecture

## AI Context & Token Optimization (Zero-Hallucination Rules)

1. **XML IS STRICTLY BANNED:** Never generate `.xml` layout files. XML forces cross-file context mapping which causes severe UI hallucinations.
2. **100% Jetpack Compose:** Write all UI in declarative Kotlin. Break large UIs into extremely small, pure `@Composable` functions.
3. **Strict Null-Safety:** Rely entirely on Kotlin's null-safety. Do not use `!!` unless absolutely necessary.
4. **Compile-Time Safety for DB:** Use SQLDelight or Room. Do NOT use raw string SQL queries in repositories.

## Project Structure

```text
com.company.project/
├── di/                          # Hilt DI modules
├── data/                        # Data layer (SQLDelight/Room DAOs, DTOs, Repositories)
├── domain/                      # Domain layer (Pure Kotlin Models, UseCases)
└── ui/                          # Presentation layer
    ├── theme/                   # Compose theming (Color, Type, Theme)
    ├── component/               # Small, reusable, modular composables
    └── screen/                  # Feature screens and ViewModels
```

## Naming Conventions

| Artifact               | Convention         | Example            |
| ---------------------- | ------------------ | ------------------ |
| Files / Composables    | `PascalCase`       | `ProfileScreen.kt` |
| Classes / Interfaces   | `PascalCase`       | `GetUserUseCase`   |
| Functions / Properties | `camelCase`        | `getUserById`      |
| Constants              | `UPPER_SNAKE_CASE` | `MAX_RETRY_COUNT`  |

## Architectural Patterns

**MVI (Model-View-Intent) + UDF:**
Every screen uses a single `ViewModel` annotated with `@HiltViewModel`. The ViewModel exposes exactly one `StateFlow<UiState>`. The View sends sealed `Intents` to the ViewModel. This eliminates race conditions and makes the reasoning traceable through a single `when(intent)` reducer block.

**Dependency Injection:**
Hilt is mandatory. Do not write manual dependency factories.

## Universal DateTime Governance

- **UTC at Rest:** Use `java.time.Instant` for all entity and DTO fields representing absolute timestamps. Store as `TEXT` (ISO-8601) or `INTEGER` (epoch ms) in SQLDelight/Room.
- **Clock Injection:** Inject `java.time.Clock` via Hilt (`@Provides @Singleton fun clock(): Clock = Clock.systemUTC()`). ViewModels and UseCases receive `Clock` via constructor. Banned: `Instant.now()`, `System.currentTimeMillis()`, `LocalDateTime.now()`.
- **API Boundary:** Transmit datetimes as epoch ms (Long) or ISO-8601 strings with offset. Parse with `Instant.parse()` or `Instant.ofEpochMilli()`. Never use `SimpleDateFormat` or `java.util.Date`.
- **UI Display:** Format for user locale using `java.time.format.DateTimeFormatter` with explicit `ZoneId`. Never use the device's default timezone implicitly.

## Testing Strategies

| Layer           | Test Type                  | Framework                     |
| --------------- | -------------------------- | ----------------------------- |
| Use cases       | Unit                       | JUnit 5 + MockK               |
| ViewModel (MVI) | Unit (Intent injection)    | JUnit 5 + Turbine (for Flows) |
| UI / Composable | Snapshot / Compose UI Test | Compose Test                  |