房间嵌套关系返回空列表答案

【问题标题】：Room Nested Relationship Returns Empty List房间嵌套关系返回空列表
【发布时间】：2022-08-24 06:19:50
【问题描述】：

我已经按照documentation 对 Room 中的嵌套关系进行建模，但尽管如此，我仍无法正确检索数据。我已经使用数据库检查器检查了表格，并且所有内容都正确填写，问题似乎出在建模关系上。

数据模型：

房间桌：

@Entity(tableName = \"journey\")
data class JourneyEntity(
    @PrimaryKey(autoGenerate = false)
    val journeyId: Int,
    val name: String,
    val created: String,
    val modified: String,
    val date: String
)

@Entity(tableName = \"agenda\")
data class AgendaEntity(
    @PrimaryKey(autoGenerate = false)
    val agendaId: Int,
    val name: String?
)

@Entity(tableName = \"stage\")
data class StageEntity(
    @Embedded val excursion: ExcursionEntity,
    @PrimaryKey(autoGenerate = false)
    val stageId: Int,
    val stageType: String
)

@Entity(primaryKeys = [\"agendaId\", \"stageId\"], tableName = \"agendaStageCrossRef\")
data class AgendaStageCrossRef(
    val agendaId: Int,
    val stageId: Int
)

@Entity(primaryKeys = [\"journeyId\", \"agendaId\"], tableName = \"journeyAgendaCrossRef\")
data class JourneyAgendaCrossRef(
    val journeyId: Int,
    val agendaId: Int
)

data class AgendasWithStages(
    @Embedded val agenda: AgendaEntity,
    @Relation(
        parentColumn = \"agendaId\",
        entityColumn = \"stageId\",
        associateBy = Junction(AgendaStageCrossRef::class)
    )
    val stages: List<StageEntity>
)

data class JourneyWithAgendas(
    @Embedded val journey: JourneyEntity,
    @Relation(
        entity = AgendaEntity::class,
        parentColumn = \"journeyId\",
        entityColumn = \"agendaId\",
    )
    val agendas: List<AgendasWithStages>
)

agendas in JourneyWithAgendas 执行后始终为空：

@Transaction
@Query(\"SELECT * FROM journey\")
suspend fun getJourneys(): List<JourneyWithAgendas>

标签： android kotlin android-room android-room-relation

【解决方案1】：

我有同样的错误。你解决了吗？

【讨论】：