根据理解，使用SunFlower实例演示hilt基本使用。

添加hilt配置

• 添加hilt gradle插件

buildscript {
    dependencies {
        classpath "com.google.dagger:hilt-android-gradle-plugin:$hiltVersion"
}
}

• 配置module使用插件进行注解处理

apply plugin: 'kotlin-kapt'
apply plugin: 'dagger.hilt.android.plugin'

• 配置hilt依赖库版本

dependencies {
    kapt "com.google.dagger:hilt-android-compiler:$rootProject.hiltVersion"
    implementation "com.google.dagger:hilt-android:$rootProject.hiltVersion"

• App启用hilt

@HiltAndroidApp
class MainApplication : Application()

数据库自动注入

常规kotlin 规范创建AppDatabase、表、查询封装Dao

• 创建数据库

@Database(entities = [GardenPlanting::class, Plant::class], version = 1, exportSchema = false)
@TypeConverters(Converters::class)
abstract class AppDatabase : RoomDatabase() {
    abstract fun gardenPlantingDao(): GardenPlantingDao
    abstract fun plantDao(): PlantDao

    companion object {

        // For Singleton instantiation
        @Volatile private var instance: AppDatabase? = null

        fun getInstance(context: Context): AppDatabase {
            return instance ?: synchronized(this) {
                instance ?: buildDatabase(context).also { instance = it }
            }
        }

        // Create and pre-populate the database. See this article for more details:
        // https://medium.com/google-developers/7-pro-tips-for-room-fbadea4bfbd1#4785
        private fun buildDatabase(context: Context): AppDatabase {
            return Room.databaseBuilder(context, AppDatabase::class.java, DATABASE_NAME)
                .addCallback(
                    object : RoomDatabase.Callback() {
                        override fun onCreate(db: SupportSQLiteDatabase) {
                            super.onCreate(db)
                            val request = OneTimeWorkRequestBuilder<SeedDatabaseWorker>().build()
                            WorkManager.getInstance(context).enqueue(request)
                        }
                    }
                )
                .build()
        }
    }
}

• 创建实体类

@Entity(tableName = "plants")
data class Plant(
    @PrimaryKey @ColumnInfo(name = "id") val plantId: String,
    val name: String,
    val description: String,
    val growZoneNumber: Int,
    val wateringInterval: Int = 7, // how often the plant should be watered, in days
    val imageUrl: String = ""
) {

    /**
     * Determines if the plant should be watered.  Returns true if [since]'s date > date of last
     * watering + watering Interval; false otherwise.
     */
    fun shouldBeWatered(since: Calendar, lastWateringDate: Calendar) =
        since > lastWateringDate.apply { add(DAY_OF_YEAR, wateringInterval) }

    override fun toString() = name
}

• 创建查询Dao

@Dao
interface PlantDao {
    @Query("SELECT * FROM plants ORDER BY name")
    fun getPlants(): Flow<List<Plant>>

    @Query("SELECT * FROM plants WHERE growZoneNumber = :growZoneNumber ORDER BY name")
    fun getPlantsWithGrowZoneNumber(growZoneNumber: Int): Flow<List<Plant>>

    @Query("SELECT * FROM plants WHERE id = :plantId")
    fun getPlant(plantId: String): Flow<Plant>

    @Insert(onConflict = OnConflictStrategy.REPLACE)
    suspend fun insertAll(plants: List<Plant>)
}

创建DatabaseModule，向外提供数据库访问方法

数据库、PlantDao等不能直接添加@Inject注解构造函数，需要创建单独的module进行对外提供。

@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()
    }

@InstallIn和@Provider上Scope关系

@InstallIn指定module要注入的生成的component，@Provider函数可以添加Scoped限定符，但是必须与@InstallIn作用域一致。
@Provider函数添加Scoped限定符后，在component范围内仅仅创建一个实例。

Android 类	生成的组件	作用域
Application	SingletonComponent	@Singleton
Activity	ActivityRetainedComponent	@ActivityRetainedScoped
ViewModel	ViewModelComponent	@ViewModelScoped
Activity	ActivityComponent	@ActivityScoped
Fragment	FragmentComponent	@FragmentScoped

将模块安装到组件后，其绑定就可以用作该组件中其他绑定的依赖项，也可以用作组件层次结构中该组件下的任何子组件中绑定的依赖项。

这个函数直接向容器提供了AppDatabase、PlantDao对象。

PlantRepository 使用 PlantDao

@Singleton
class PlantRepository @Inject constructor(private val plantDao: PlantDao) {

    fun getPlants() = plantDao.getPlants()

    fun getPlant(plantId: String) = plantDao.getPlant(plantId)

    fun getPlantsWithGrowZoneNumber(growZoneNumber: Int) =
        plantDao.getPlantsWithGrowZoneNumber(growZoneNumber)
}

@Singleton 这个和dagger2 @Module Provider方法限定符效果一样，标志在注入Component范围内单例。
@Inject 标志当component需要注入PlantRepository对象时，可以直接调用该函数进行获取。
@Inject constructor 参数plantDao，标志component使用PlantRepository对象时，需要提供的对象。

ViewModel使用PlantRepository

@HiltViewModel标志ViewModel自动进行构造函数注入
且必须存在@Inject修饰的构造函数

@HiltViewModel
class PlantDetailViewModel @Inject constructor(
    savedStateHandle: SavedStateHandle,
    plantRepository: PlantRepository,
    private val gardenPlantingRepository: GardenPlantingRepository,
) : ViewModel() {

    val plantId: String = savedStateHandle.get<String>(PLANT_ID_SAVED_STATE_KEY)!!

Fragment声明需要进行注入

@AndroidEntryPoint标志注入入口点
@AndroidEntryPoint 标志，当前Activity、Fragment需要进行hilt注入。
注：Fragment添加后，其所在的Activity同样必须添加

@AndroidEntryPoint
class GardenActivity : AppCompatActivity() {



@AndroidEntryPoint
class PlantDetailFragment : Fragment() {

    private val plantDetailViewModel: PlantDetailViewModel by viewModels()

sunflower 仓库地址

gd771747384/sunflower