---
id: android-hilt-di-patterns
title: Android Hilt — DI 모듈과 스코프
category: Coding
status: draft
source_trust_level: B
verification_status: conceptual
created_at: 2026-05-09
updated_at: 2026-05-09
tags: [android, hilt, di, dagger, vibe-coding]
tech_stack: { language: "Kotlin / Hilt", applicable_to: ["Android"] }
applied_in: []
aliases: [@HiltAndroidApp, @Module, @Provides, ViewModelComponent]
---

# Android Hilt — DI

> Dagger 의 Android 친화 wrapper. **컴포넌트 = 스코프**. ApplicationComponent (Singleton), ActivityComponent, FragmentComponent, ViewModelComponent. 잘못된 스코프 = leak 또는 잘못된 인스턴스 공유.

## 📖 핵심 개념
- @HiltAndroidApp: Application 클래스에. 부팅.
- @AndroidEntryPoint: Activity / Fragment / View / Service 에.
- @HiltViewModel: ViewModel 자동 주입.
- @Module + @InstallIn: 어떤 컴포넌트에 binding.

## 💻 코드 패턴

### 부팅
```kotlin
@HiltAndroidApp
class App : Application()

// AndroidManifest.xml — name=".App"
```

### Module — 외부 라이브러리 binding
```kotlin
@Module
@InstallIn(SingletonComponent::class)
object NetworkModule {

    @Provides @Singleton
    fun retrofit(): Retrofit = Retrofit.Builder()
        .baseUrl("https://api.example.com/")
        .addConverterFactory(MoshiConverterFactory.create())
        .build()

    @Provides @Singleton
    fun userApi(retrofit: Retrofit): UserApi = retrofit.create(UserApi::class.java)
}

@Module
@InstallIn(SingletonComponent::class)
abstract class RepoModule {
    @Binds @Singleton
    abstract fun bindUserRepo(impl: UserRepoImpl): UserRepo
}
```

### Scoped repository
```kotlin
@Singleton
class UserRepo @Inject constructor(
    private val api: UserApi,
    private val dao: UserDao,
) { ... }
```

### ViewModel 주입
```kotlin
@HiltViewModel
class ProfileViewModel @Inject constructor(
    private val repo: UserRepo,
    private val savedState: SavedStateHandle,
) : ViewModel() { ... }
```

### Compose
```kotlin
@Composable
fun ProfileScreen(viewModel: ProfileViewModel = hiltViewModel()) { ... }
```

### Worker 주입
```kotlin
@HiltWorker
class SyncWorker @AssistedInject constructor(
    @Assisted ctx: Context,
    @Assisted params: WorkerParameters,
    private val repo: SyncRepo,
) : CoroutineWorker(ctx, params) { ... }

// App 에서
@HiltAndroidApp
class App : Application(), Configuration.Provider {
    @Inject lateinit var workerFactory: HiltWorkerFactory
    override val workManagerConfiguration: Configuration
        get() = Configuration.Builder().setWorkerFactory(workerFactory).build()
}
```

### Qualifier — 같은 타입 다른 인스턴스
```kotlin
@Qualifier annotation class Authed
@Qualifier annotation class Public

@Provides @Singleton @Authed
fun authedClient(): OkHttpClient = OkHttpClient.Builder().addInterceptor(AuthInterceptor()).build()

@Provides @Singleton @Public
fun publicClient(): OkHttpClient = OkHttpClient()

class Repo @Inject constructor(@Authed private val client: OkHttpClient) { ... }
```

## 🤔 의사결정 기준
| 인스턴스 lifecycle | 스코프 |
|---|---|
| 앱 전체 (DB, network client, repo) | @Singleton in SingletonComponent |
| Activity 동안 (navigation graph) | @ActivityRetainedScoped |
| ViewModel 동안 | @ViewModelScoped |
| Fragment 동안 | @FragmentScoped |
| 매번 새로 | scope 없음 (default) |

## ❌ 안티패턴
- **모든 곳 @Singleton**: 큰 객체 메모리 영구 점유. 필요한 곳만.
- **Activity scope 인데 ViewModel 에 주입**: ViewModel 이 Activity 보다 오래 → leak.
- **Context 잘못된 종류**: ApplicationContext vs ActivityContext. 가장 작은 scope.
- **모듈을 잘못된 컴포넌트에 InstallIn**: 의존성 못 찾음.
- **@Provides 와 @Binds 혼용 + 같은 타입**: ambiguous.
- **테스트 환경에서 production module 그대로**: 외부 의존. @TestInstallIn 으로 fake.
- **ViewModel constructor 에 Context 주입**: leak. @ApplicationContext 만.

## 🤖 LLM 활용 힌트
- 신규 Android = Hilt 디폴트.
- Singleton vs ViewModelScoped 명확히.
- Test 는 hiltRules + fake module.

## 🔗 관련 문서
- [[Android_Room_Patterns]]
- [[Android_WorkManager_Patterns]]
