Question

我有一个这样的实体类

@Entity
data class NewsResponse(
        @PrimaryKey
        @field:SerializedName("news")
        val news: ArrayList<NewsItem?>? = null
)

NewsItem类就是这样

@Entity
data class NewsItem(

    @field:SerializedName("imgUrl")
    val imgUrl: String? = null,

    @field:SerializedName("link")
    val link: String? = null,

    @field:SerializedName("description")
    val description: String? = null,

    @PrimaryKey
    @field:SerializedName("title")
    val title: String? = null
)

然后我有DAO这样的NewsResponse

@Dao
interface NewsRespDao {
    @Query("SELECT * FROM NewsItem")
    fun getNewsItems():LiveData<List<NewsItem>>

    @Insert(onConflict = REPLACE)
    fun insertNews(newsList: List<NewsItem?>?)

    @Query("DELETE FROM NewsItem")
    fun deleteAll()
}

我也有一个这样定义的TypeConverter

class NewsConverter {
    @TypeConverter
    fun fromString(value:String):ArrayList<NewsItem>{
        val listType = object : TypeToken<ArrayList<NewsItem>>() {

        }.type
        return Gson().fromJson(value, listType)
    }

    fun fromArrayList(list:ArrayList<NewsItem>):String{
        val gson = Gson()
        return gson.toJson(list)
    }
}

然后在RoomDatabase类中，我已经定义了这样的TypeConverter批注

@Database(entities = arrayOf(Source::class,NewsResponse::class),version = 1)
@TypeConverters(NewsConverter::class)
abstract class SourceDataBase : RoomDatabase(){
    abstract fun sourceDao():SourceDao

    companion object {
        private var INSTANCE:SourceDataBase?=null

        fun getInstance(context: Context):SourceDataBase?{
            if(INSTANCE == null){
                synchronized(SourceDataBase::class){
                    INSTANCE = Room.databaseBuilder(context.applicationContext,SourceDataBase::class.java,"source.db")
                            .build()
                }
            }
            return INSTANCE
        }
        fun destroyInstance(){
            INSTANCE=null
        }

    }


}

但是，每当我尝试运行时，都会出现一条错误消息

Cannot figure out how to save this field into database. You can consider adding a type converter for it.

要保存对象列表，一种方法是定义TypeConverter，而我已经定义了它，但仍然出现错误。我在这里做错了什么？谢谢

Answer 1

您不需要NewsConverter。您不需要将NewsResponse作为实体。您的实体必须是这样的：

@Database(entities = arrayOf(Source::class,NewsItem::class),version = 1)
abstract class SourceDataBase : RoomDatabase(){

然后一切都应该正常工作

会议室数据库未考虑类型转换器

1 个答案: