ViewModel中的Android Hilt Dagger 注入(inject)接口(interface)@ViewModelInject得到了UninitializedPropertyAccessException

Question

我正在尝试 Hilt 代码实验室
https://codelabs.developers.google.com/codelabs/android-hilt#10
它与 Activity 和 Fragment 配合得很好
记录器是一个 RoomDB
然后我尝试用这个 article 将记录器注入(inject)到 viewModel 中。
通过添加

implementation "androidx.hilt:hilt-lifecycle-viewmodel
    :1.0.0-alpha02"
kapt 'androidx.hilt:hilt-compiler:1.0.0-alpha02'

查看模型代码

class RecordFragmentViewModel @ViewModelInject constructor(@Assisted private val savedStateHandle: SavedStateHandle) :
    ViewModel() {
    @DatabaseLogger
    @Inject
    lateinit var logger: LoggerDataSource

类记录器注入(inject)

 class LoggerLocalDataSource 
@Inject constructor(private val logDao: LogDao) : LoggerDataSource {

记录模块

@Qualifier
annotation class InMemoryLogger

@Qualifier
annotation class DatabaseLogger

@InstallIn(ApplicationComponent::class)
@Module
abstract class LoggingDatabaseModule {

    @DatabaseLogger
    @Singleton
    @Binds
    abstract fun bindDatabaseLogger(impl: LoggerLocalDataSource): LoggerDataSource
}

@InstallIn(ActivityComponent::class)
@Module
abstract class LoggingInMemoryModule {

    @InMemoryLogger
    @ActivityScoped
    @Binds
    abstract fun bindInMemoryLogger(impl: LoggerInMemoryDataSource): LoggerDataSource
}

数据库模块

@InstallIn(ApplicationComponent::class)
@Module
object DatabaseModule {

    @Provides
    @Singleton
    fun provideDatabase(@ApplicationContext appContext: Context): AppDatabase {
        return Room.databaseBuilder(
            appContext,
            AppDatabase::class.java,
            "logging.db"
        ).build()
    }

    @Provides
    fun provideLogDao(database: AppDatabase): LogDao {
        return database.logDao()
    }
}

它的编译和运行没有错误。
但是，我使用调试来观察记录器及其得到的。

Method threw 'kotlin.UninitializedPropertyAccessException' exception.

我在运行时调用 logger.something() 它的抛出

Fatal Exception: kotlin.UninitializedPropertyAccessException
lateinit property logger has not been initialized

更多信息
https://dagger.dev/hilt/migration-guide.html
https://codelabs.developers.google.com/codelabs/android-hilt#10
https://medium.com/mobile-app-development-publication/injecting-viewmodel-with-dagger-hilt-54ca2e433865

Answer 1

由于 LoggerDataSource 是一个接口(interface)，我们需要指定我们需要注入(inject)的实现。感谢@Andrew 提供注入(inject)构造函数的想法

class RecordFragmentViewModel
@ViewModelInject
constructor(@Assisted private val savedStateHandle: SavedStateHandle,
            @DatabaseLogger private val logger: LoggerDataSource) :
    ViewModel(), LifecycleObserver {

指定

@Qualifier
annotation class InMemoryLogger

@Qualifier
annotation class DatabaseLogger

@InstallIn(ApplicationComponent::class)
@Module
abstract class LoggingDatabaseModule {

    @DatabaseLogger
    @Singleton
    @Binds
    abstract fun bindDatabaseLogger(impl: LoggerLocalDataSource): LoggerDataSource
}

@InstallIn(ActivityComponent::class)
@Module
abstract class LoggingInMemoryModule {

    @InMemoryLogger
    @ActivityScoped
    @Binds
    abstract fun bindInMemoryLogger(impl: LoggerInMemoryDataSource): LoggerDataSource
}