//프로젝트 builde.gradle
buildscript {
    ...
    dependencies {
        ...
        classpath 'com.google.dagger:hilt-android-gradle-plugin:2.28-alpha'
    }
}

//앱 builde.gradle
...
apply plugin: 'kotlin-kapt'
apply plugin: 'dagger.hilt.android.plugin'

android {
    ...
}

dependencies {
    implementation "com.google.dagger:hilt-android:2.28-alpha"
    kapt "com.google.dagger:hilt-android-compiler:2.28-alpha"
    
    //test
    kaptAndroidTest "com.google.dagger:hilt-android-compiler:$rootProject.hiltVersion"
    androidTestImplementation "com.google.dagger:hilt-android-testing:$rootProject.hiltVersion"
}

import android.app.Application
import dagger.hilt.android.HiltAndroidApp

@HiltAndroidApp
class MainApplication : Application()

@AndroidEntryPoint
class GalleryFragment : Fragment() {

@AndroidEntryPoint
class GardenFragment : Fragment() {

@AndroidEntryPoint
class HomeViewPagerFragment : Fragment() {

@AndroidEntryPoint
class PlantDetailFragment : Fragment() {

@AndroidEntryPoint
class PlantListFragment : Fragment() {

@HiltViewModel
class GalleryViewModel @Inject constructor(
    private val repository: UnsplashRepository
) : ViewModel() {

@HiltViewModel
class GardenPlantingListViewModel @Inject internal constructor(
    gardenPlantingRepository: GardenPlantingRepository
) : ViewModel() {

/**
 * The ViewModel for [PlantListFragment].
 */
@HiltViewModel
class PlantListViewModel @Inject internal constructor(
    plantRepository: PlantRepository,
    private val savedStateHandle: SavedStateHandle
) : ViewModel() {

/**
 * The ViewModel used in [PlantDetailFragment].
 */
class PlantDetailViewModel @AssistedInject constructor(
    plantRepository: PlantRepository,
    private val gardenPlantingRepository: GardenPlantingRepository,
    @Assisted private val plantId: String
) : ViewModel() {

@AndroidEntryPoint
class PlantDetailFragment : Fragment() {

    private val args: PlantDetailFragmentArgs by navArgs()

    @Inject
    lateinit var plantDetailViewModelFactory: PlantDetailViewModelFactory

    private val plantDetailViewModel: PlantDetailViewModel by viewModels {
        PlantDetailViewModel.provideFactory(plantDetailViewModelFactory, args.plantId)
    }

class PlantDetailViewModel @AssistedInject constructor(
    plantRepository: PlantRepository,
    private val gardenPlantingRepository: GardenPlantingRepository,
    @Assisted private val plantId: String
) : ViewModel() {

    val isPlanted = gardenPlantingRepository.isPlanted(plantId).asLiveData()
    val plant = plantRepository.getPlant(plantId).asLiveData()

    fun addPlantToGarden() {
        viewModelScope.launch {
            gardenPlantingRepository.createGardenPlanting(plantId)
        }
    }

    fun hasValidUnsplashKey() = (BuildConfig.UNSPLASH_ACCESS_KEY != "null")

    companion object {
        fun provideFactory(
            assistedFactory: PlantDetailViewModelFactory,
            plantId: String
        ): ViewModelProvider.Factory = object : ViewModelProvider.Factory {
            @Suppress("UNCHECKED_CAST")
            override fun <T : ViewModel?> create(modelClass: Class<T>): T {
                return assistedFactory.create(plantId) as T
            }
        }
    }
}

@AssistedFactory
interface PlantDetailViewModelFactory {
    fun create(plantId: String): PlantDetailViewModel
}

@Singleton
class GardenPlantingRepository @Inject constructor(
    private val gardenPlantingDao: GardenPlantingDao
) {

package com.google.samples.apps.sunflower.data

import javax.inject.Inject
import javax.inject.Singleton

/*@Singleton으로 어디서나 동일한 객체를 제공합니다*/
/**
 * Repository module for handling data operations.
 *
 * Collecting from the Flows in [PlantDao] is main-safe.  Room supports Coroutines and moves the
 * query execution off of the main thread.
 */
@Singleton
class PlantRepository @Inject constructor(private val plantDao: PlantDao) {

import kotlinx.coroutines.flow.Flow
import javax.inject.Inject

class UnsplashRepository @Inject constructor(private val service: UnsplashService) {

/**
 * Used to connect to the Unsplash API to fetch photos
 */
interface UnsplashService {

    @GET("search/photos")
    suspend fun searchPhotos(
        @Query("query") query: String,
        @Query("page") page: Int,
        @Query("per_page") perPage: Int,
        @Query("client_id") clientId: String = BuildConfig.UNSPLASH_ACCESS_KEY
    ): UnsplashSearchResponse

@InstallIn(SingletonComponent::class)
@Module
class NetworkModule {

    @Singleton
    @Provides
    fun provideUnsplashService(): UnsplashService {
        return UnsplashService.create()
    }
}

@InstallIn(SingletonComponent::class)
@Module
class DatabaseModule {

    @Singleton
    @Provides
    fun provideAppDatabase(@ApplicationContext context: Context): AppDatabase {
        return AppDatabase.getInstance(context)
    }

    @Provides
    fun providePlantDao(appDatabase: AppDatabase): PlantDao {
        return appDatabase.plantDao()
    }

    @Provides
    fun provideGardenPlantingDao(appDatabase: AppDatabase): GardenPlantingDao {
        return appDatabase.gardenPlantingDao()
    }
}

/** A Hilt component for singleton bindings. */
@Singleton
@DefineComponent
public interface SingletonComponent {}

@InstallIn(SingletonComponent::class)
@Module
class NetworkModule {

    @Singleton
    @Provides
    fun provideUnsplashService(): UnsplashService {
        return UnsplashService.create()
    }
}

interface UnsplashService {

    @GET("search/photos")
    suspend fun searchPhotos(
        @Query("query") query: String,
        @Query("page") page: Int,
        @Query("per_page") perPage: Int,
        @Query("client_id") clientId: String = BuildConfig.UNSPLASH_ACCESS_KEY
    ): UnsplashSearchResponse

    companion object {
        private const val BASE_URL = "https://api.unsplash.com/"

        fun create(): UnsplashService {
            val logger = HttpLoggingInterceptor().apply { level = Level.BASIC }

            val client = OkHttpClient.Builder()
                .addInterceptor(logger)
                .build()

            return Retrofit.Builder()
                .baseUrl(BASE_URL)
                .client(client)
                .addConverterFactory(GsonConverterFactory.create())
                .build()
                .create(UnsplashService::class.java)
        }
    }
}