Using Dependency Injection with Hilt

plugins {
    id 'com.google.dagger.hilt.android'
}

dependencies {
    implementation 'com.google.dagger:hilt-android:2.51.1'
    annotationProcessor 'com.google.dagger:hilt-android-compiler:2.51.1'
}

@HiltAndroidApp
class MyApplication : Application() {
    // Hilt will now be available for dependency injection
}

@AndroidEntryPoint
class MainActivity : AppCompatActivity() {
    @Inject
    lateinit var userRepository: UserRepository

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        // userRepository is now injected
        val user = userRepository.getUser(1)
    }
}

@AndroidEntryPoint
class UserFragment : Fragment() {
    @Inject
    lateinit var userViewModel: UserViewModel

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        // userViewModel is now injected
    }
}

@Module
@InstallIn(SingletonComponent::class)
object DatabaseModule {
    @Provides
    @Singleton
    fun provideDatabase(context: Context): AppDatabase {
        return Room.databaseBuilder(
            context,
            AppDatabase::class.java,
            "app_database"
        ).build()
    }
}

@Module
@InstallIn(ActivityComponent::class)
object ActivityModule {
    @Provides
    @ActivityScoped
    fun provideViewModel(): MyViewModel {
        return MyViewModel()
    }
}

@Singleton<br>class DatabaseManager @Inject constructor() {<br>    fun saveData(data: String) { /* ... */ }<br>}

@Named("production")<br>class ProductionApiClient @Inject constructor() : ApiClient {<br>    override fun fetch(): String = "Production Data"<br>}<br><br>@Named("staging")<br>class StagingApiClient @Inject constructor() : ApiClient {<br>    override fun fetch(): String = "Staging Data"<br>}

@Repository<br>class UserRepository @Inject constructor(<br>&nbsp;&nbsp;private val apiService: ApiService,<br>&nbsp;&nbsp;private val database: AppDatabase<br>) {<br>&nbsp;&nbsp;fun fetchUser(id: String) = apiService.fetchUser(id)<br>}

@HiltViewModel<br>class UserViewModel @Inject constructor(<br>&nbsp;&nbsp;private val repository: UserRepository,<br>&nbsp;&nbsp;private val dispatcher: CoroutineDispatcher = Dispatchers.IO<br>) : ViewModel() {<br>&nbsp;&nbsp;fun loadUser(id: String) = viewModelScope.launch(dispatcher) {<br>&nbsp;&nbsp;&nbsp;&nbsp;val user = repository.fetchUser(id)<br>&nbsp;&nbsp;&nbsp;&nbsp;// Update UI<br>&nbsp;&nbsp;}<br>}

@Singleton
class DatabaseManager @Inject constructor(
    private val database: RoomDatabase
) {
    fun saveData(data: String) {
        // Save data logic here
    }
}

@ActivityScoped
class NetworkManager @Inject constructor(
    private val apiService: ApiService
) {
    fun fetchData(): Flow<Data> {
        return apiService.fetchData()
    }
}

import androidx.hilt.lifecycle.ViewModelInject
import androidx.lifecycle.ViewModel

@HiltViewModel
class MyViewModel @ViewModelInject constructor(
    private val repository: MyRepository
) : HiltViewModel() {
    // ViewModel logic here
}

@Module
@InstallIn(SingletonComponent::class)
object NetworkModule {
    @Provides
    @Named("production")
    fun provideProductionApi(): ApiInterface = ProductionApi()

    @Provides
    @Named("staging")
    fun provideStagingApi(): ApiInterface = StagingApi()
}

@Singleton
class Repository @Inject constructor(
    @Named("production") private val api: ApiInterface
)

@Qualifier
@Retention(AnnotationRetention.BINARY)
annotation class Production

@Module
@InstallIn(SingletonComponent::class)
object NetworkModule {
    @Provides
    @Production
    fun provideProductionApi(): ApiInterface = ProductionApi()
}

@Singleton
class Repository @Inject constructor(
    @Production private val api: ApiInterface
)

@HiltAndroidTest
class UserRepositoryTest {

    @Inject
    @Mock
    lateinit var mockUserDao: UserDao

    @Inject
    @Mock
    lateinit var mockNetworkManager: NetworkManager

    @Test
    fun `test fetch user data`() {
        // Given
        val expectedUser = User("1", "John Doe")
        whenever(mockUserDao.fetchUserById("1")).thenReturn(expectedUser)

        // When
        val result = userRepository.fetchUser("1")

        // Then
        assertEquals(expectedUser, result)
    }
}

@Module
@InstallIn(ActivityComponent::class)
@EntryPoint
interface MyEntryPoint {
    fun provideSomeService(): SomeService
}

class MyActivity : AppCompatActivity() {
    private val entryPoint by lazy {
        EntryPointAccessors.fromActivity(this, MyEntryPoint::class.java)
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        val service = entryPoint.provideSomeService()
        // Use the service
    }
}