使用带有短柄的类型转换器时出错

Question

我是一个依赖注入的新手，目前正在使用dagger-hilt。我必须使用类型转换器才能在实体中插入列表。

在运行时，我面临崩溃，因为数据库配置中缺少转换器，尽管我正在添加它。

下面是关于类型转换器、数据库类和应用程序模块的代码

@ProvidedTypeConverter
class BundleConverter {
    @TypeConverter
    fun fromPackageBundleList(countryLang: List<PackageBundle?>?): String? {
        if (countryLang == null) {
            return null
        }
        val gson = Gson()
        val type: Type = object : TypeToken<List<PackageBundle?>?>() {}.type
        return gson.toJson(countryLang, type)
    }

    @TypeConverter
    fun toPackageBundleList(countryLangString: String?): List<PackageBundle>? {
        if (countryLangString == null) {
            return null
        }
        val gson = Gson()
        val type: Type = object : TypeToken<List<PackageBundle?>?>() {}.type
        return gson.fromJson<List<PackageBundle>>(countryLangString, type)
    }
}

@Database(
    entities = [Service::class,SoundEffect::class],
    version = 3,
    exportSchema = false
)
@TypeConverters(BundleConverter::class)
abstract class UserDatabase : RoomDatabase() {

    abstract fun getYourDao(): UserDao
}

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

    @Singleton
    @Provides
    fun provideYourDatabase(
        @ApplicationContext app: Context
    ) = Room.databaseBuilder(
        app,
        UserDatabase::class.java,
        "your_db_name"
    )
        .addTypeConverter(BundleConverter::class)
        .build()

    @Singleton
    @Provides
    fun provideYourDao(db: UserDatabase) = db.getYourDao()
}

Answer 1

尝试从数据库转换器类中删除可选值处理：

class BundleConverter {
    @TypeConverter
    fun fromPackageBundleList(countryLang: List<PackageBundle>): String =
        return Gson().toJson(countryLang)

    @TypeConverter
    fun toPackageBundleList(countryLangString: String): List<PackageBundle> {
        val type: Type = object : TypeToken<List<PackageBundle>>() {}.type
        return Gson().fromJson(countryLangString, type)
    }
}