错误：[Dagger/MissingBinding]。如果没有 @Provides 注释的方法，则无法提供

Question

我尝试使用 Hilt 将天气存储库注入到我的视图模型中，但收到以下错误消息：

如果没有 @Provides 注释的方法，则无法提供 WeatherDao。
公共抽象静态类 SingletonC 实现 WeatherApplication_GenerateInjector

天气 DAO：

@Dao
interface WeatherDao {
    @Insert(onConflict = OnConflictStrategy.REPLACE)
    suspend fun insertWeatherItem(weatherItem: WeatherItem)
    @Query("DELETE FROM WEATHERITEM WHERE cityName = :cityName")
    suspend fun deleteWeatherItem(cityName: String)
    @Query("SELECT * FROM WEATHERITEM WHERE cityId = :id")
    fun getWeatherItem(id: Int): Flow<WeatherItem>
    @Query("SELECT * FROM WEATHERITEM")
    fun getAllWeatherItems(): Flow<List<WeatherItem>>
}

天气知识库：

class WeatherRepository @Inject constructor(private val weatherDao: WeatherDao) {
     suspend fun insertWeatherItem(weatherItem: WeatherItem) = weatherDao.insertWeatherItem(weatherItem)
     suspend fun deleteWeatherItem(cityName: String) = weatherDao.deleteWeatherItem(cityName)
     fun getWeatherItem(id: Int): Flow<WeatherItem> = weatherDao.getWeatherItem(id)
     fun getAllWeatherItems(): Flow<List<WeatherItem>> = weatherDao.getAllWeatherItems()
}

天气数据库：

@Database(entities = [WeatherItem::class] ,version = 1)
abstract class WeatherDatabase :RoomDatabase(){
    abstract fun weatherDao(): WeatherDao
}

天气模块：

@Module
@InstallIn(ActivityComponent::class)
object WeatherModule {
    @Provides
    @Singleton
    fun provideDatabase(@ApplicationContext context: Context): WeatherDatabase {
        return Room.databaseBuilder(
            context,
            WeatherDatabase::class.java,
            "WeatherDatabase")
            .fallbackToDestructiveMigration()
            .build()
    }
    @Provides
    @Singleton
    fun provideUserDao(weatherDatabase: WeatherDatabase): WeatherDao {
        return weatherDatabase.weatherDao()
    }

    @Provides
    @Singleton
    fun provideWeatherRepository(weatherDao: WeatherDao): WeatherRepository {
        return WeatherRepository(weatherDao)
    }
}

天气视图模型：

@HiltViewModel
class WeatherViewModel @Inject constructor(
    private val weatherRepository: WeatherRepository,
) : ViewModel()

主要活动：

@AndroidEntryPoint
class MainActivity : ComponentActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        val viewModel: WeatherViewModel by viewModels()

        setContent {
           
            WindSpellTheme(darkTheme = darkTheme) {
                Surface(
                    modifier = Modifier.fillMaxSize(),
                    color = MaterialTheme.colorScheme.background
                ) {
                    MainScreen(viewModel) {
                        
                    }
                }
            }
        }
    }
}

应用：

@HiltAndroidApp
class WeatherApplication: Application()

Hilt版本是2.47

Answer 1

请尝试从

@Inject constructor

中删除

class WeatherRepository @Inject constructor(private val weatherDao: WeatherDao)

，因为您已经在

WeatherModule

中拥有它。

目前应该可以工作。

P.S. 如果您稍后决定制作

WeatherRepository

及其实现的接口，例如

WeatherRepositoryImpl

，您可以按如下方式进行：

@Singleton
class WeatherRepositoryImpl @Inject constructor(private val weatherDao: WeatherDao): WeatherRepository {
    //implementation
}

然后，在某些

Module

中，这是一个接口或抽象类：

@Binds
@Singleton
fun bindWeatherRepository(impl: WeatherRepositoryImpl): WeatherRepository