android - 错误 : Query method parameters should either be a type that can be converted into a database column or a List/Array that contains such type

Question

我的类型转换器

import androidx.room.TypeConverter
import com.amin.movie.vo.Query

object QueryTypeConverter {
    @TypeConverter
    @JvmStatic
    fun queryToString(query: Query?): String? = if (query != null) Query.toJson(query) else null

    @TypeConverter
    @JvmStatic
    fun stringToQuery(data: String?): Query? = if (data != null) stringToQuery(data) else null
}

实体是

import androidx.room.Entity
import androidx.room.PrimaryKey
import androidx.room.TypeConverters
import com.amin.movie.db.MovieTypeConverters
import com.amin.movie.db.QueryTypeConverter
import com.google.gson.annotations.SerializedName

@Entity
@TypeConverters(QueryTypeConverter::class)
data class MovieSearchResult(
        // and other fields
        @PrimaryKey
        val query: Query
)

当我想做我的项目时发生了这个错误错误:查询方法参数应该是可以转换为数据库列的类型或包含此类类型的列表/数组。您可以考虑为此添加一个类型适配器。

Answer 1

我已经在 latest release of Room at this time 上测试了您的代码它对我有用。我创建了一个 Database和一个 Dao以确保它正常工作并且一切看起来都很好。
尽管您的方法现在有效，但这不是他们在 Room documentation for kotlin 的 kotlin 示例中显示的方法. Here是他们在 TypeConverter 上的例子这就是它如何适用于您的具体情况(我还提供了 Database 和 Dao 我制作的):

// The query class wasn't provided so this is just a simple
// class with a toJson static method
data class Query(var query: String) {
    companion object {
        fun toJson(query: Query): String {
            return query.query
        }
    }
}

@Entity
@TypeConverters(QueryTypeConverter::class)
data class MovieSearchResult(
    // and other fields
    @PrimaryKey
    val query: Query
)

class QueryTypeConverter {
    @TypeConverter
    fun queryToString(query: Query?): String? = if (query != null) Query.toJson(query) else null

    @TypeConverter
    fun stringToQuery(data: String?): Query? = if (data != null) stringToQuery(data) else null
}

@Dao
interface MovieSearchResultDao {
    @Insert
    fun insert(r: MovieSearchResult)

    @Update
    fun update(r: MovieSearchResult)

    @Delete
    fun delete(r: MovieSearchResult)
}

@Database(entities=arrayOf(MovieSearchResult::class), version = 1, exportSchema = false)
abstract class AppDatabase : RoomDatabase() {
    abstract fun dao(): MovieSearchResultDao
    companion object {
        private var DB: AppDatabase? = null;
        public fun instance(context: Context): AppDatabase {
            var db = DB
            if (db == null) {
                db = Room.databaseBuilder(
                    context,
                    AppDatabase::class.java, "database-name"
                ).build()
                DB = db
            }
            return db
        }
    }
}