Android viewModel 中的 Hilt dagger 注入接口 @ViewModelInject 得到 UninitializedPropertyAccessException

Question

我嘗試使用 Hiltcodelab https://codelabs.developers.google.com/codelabs/android-hilt#10

它與 Activity 和 Fragment 配合得很好

記錄器是一個 RoomDB

然后我嘗試用這篇文章將記錄器注入viewModel

通過添加

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

查看模型代碼

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

Class 記錄器注入

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

記錄模塊

@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
}

數據庫模塊

@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()
    }
}

它的編譯和運行沒有錯誤。 但是，我使用調試來觀察記錄器及其得到的。

Method threw 'kotlin.UninitializedPropertyAccessException' exception.

我在運行時調用 logger.something() 它的拋出

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

由於 LoggerDataSource 是一個接口，我們需要指定我們需要注入的實現。 感謝@Andrew 提供注入構造函數的想法

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
}