3路交叉表在房间Android

如何解决3路交叉表在房间Android

我正在努力实现以下目标

我有以下实体

@Entity(tableName = "workspace_table")
data class WorkSpace(
    @PrimaryKey
    val workSpaceId:Long,.....
)

@Entity(tableName = "widget_table")
data class Widget(
    val widgetId:Long,.......
)

@Entity(tableName = "Feed_table")
data class Feed(
    val FeedId:Long,.......
)

我想要的 3 表如下 POJO

data class MergedData(
@Embedded workSpace:WorkSpace,@Embedded widget:List<Widget>,@Embedded Feeds:List<Feed>,)

关系是这样的

workSpaceId|widgetId|FeedId|
  1        | 1      | 2
  1        | 1      | 1    |
  2        | 1      | 2
  2        | 2      | 1

基本上，工作区和小部件以及小部件和提要之间存在多对多的关系当三个表都参加时，他们应该走到一起

我浏览了指南 https://developer.android.com/training/data-storage/room/relationships

并尝试在小部件和工作区以及提要和小部件之间映射两种方式但是那些我什至无法用它构建的

我尝试使用 Workspace 和 Widget 进行一对多，以及使用 Widget 和 Feed 进行多对多然后我会在我的工作区中获取我不想要的小部件的提要。

此时我真的很困惑，任何朝正确方向的推动都将不胜感激

更新

有了下面迈克的回答，我就明白了

2021-04-04 12:16:06.097 10237-10291/com.example.datacreation D/MainActivty: Meta data [IntersectionWithWorkSpaceWidgetFeed(workSpace=WorkSpace(workSpaceId=2,associatedUserId=test,workSpaceName=Demo),widget=WidgetMetaData(widgetId=11,widgetName=Widget1,backgroundColor=None,widgetType=normal,dataUrl=www),Feed=Feed(FeedId=2,FeedName=Feed2,count=0,asyncInterval=1234)),IntersectionWithWorkSpaceWidgetFeed(workSpace=WorkSpace(workSpaceId=2,widget=WidgetMetaData(widgetId=12,widgetName=Widget2,widgetType=normal,Feed=Feed(FeedId=1,FeedName=Feed1,count=2,associatedUserId=igvuser,widget=WidgetMetaData(widgetId=13,widgetName=Widget3,asyncInterval=1234))]

足够接近我原来的 MergedData POJO。谢谢迈克。

解决方法

我相信您想要一个 3 路映射表。每行由 3 列组成，WorkSpaceId、WidgetId 和 FeedId 以及由所有 3 列组成的主键。

假设这是一个工作示例：-

3 个基本实体：

工作区

@Entity(
    tableName = "workspace_table",)
data class WorkSpace(
    @PrimaryKey
    val workSpaceId:Long,val workPlaceName: String
)

小工具

@Entity(
    tableName = "widget_table",)
data class Widget(
    @PrimaryKey
    val widgetId:Long,val widgetName: String
)

饲料

@Entity(tableName = "feed_table")
data class Feed(
    @PrimaryKey
    val feedId:Long,val feedName: String
)

新的映射表WorkSpaceWidgetFeedIntersectionMap

@Entity(
    tableName = "workspace_widget_feed_mapping_table",foreignKeys = [
        ForeignKey(
            entity = WorkSpace::class,parentColumns = ["workSpaceId"],childColumns = ["workSpaceId_map"]
        ),ForeignKey(
            entity = Widget::class,parentColumns = ["widgetId"],childColumns = ["widgetId_map"]
        ),ForeignKey(
            entity = Feed::class,parentColumns = ["feedId"],childColumns = ["feedId_map"]
        )
    ],primaryKeys = ["workSpaceId_map","widgetId_map","feedId_map"],)
data class WorkSpaceWidgetFeedIntersectionMap(

    @NonNull
    val workSpaceId_map: Long,@NonNull
    val widgetId_map: Long,@NonNull
    val feedId_map: Long
)

外键是可选的

道的AllDao

@Dao
interface AllDao {

    @Insert
    fun insertWorkSpace(workSpace: WorkSpace): Long
    @Insert
    fun insertWidget(widget: Widget): Long
    @Insert
    fun insertFeed(feed: Feed): Long
    @Insert
    fun insertWorkSpaceWidgetFeedMap(workSpaceWidgetFeedIntersectionMap: WorkSpaceWidgetFeedIntersectionMap): Long


    @Query("DELETE FROM workspace_table")
    fun clearWorkSpaceTable(): Int
    @Query("DELETE FROM widget_table")
    fun clearWidgetTable(): Int
    @Query("DELETE FROM feed_table")
    fun clearFeedTable(): Int

    @Query("DELETE FROM workspace_widget_feed_mapping_table")
    fun clearWorkSpaceWidgetFeedMap(): Int

    @Query("SELECT * FROM workspace_widget_feed_mapping_table")
    fun getWorkSpaceWidgetFeedIntersections(): List<WorkSpaceWidgetFeedIntersectionMap>

}

数据库MyDatabase

@Database(entities = [WorkSpace::class,Widget::class,Feed::class,WorkSpaceWidgetFeedIntersectionMap::class],version = 1)
abstract class MyDatabase: RoomDatabase() {
    abstract fun getAllDoa(): AllDao
}

最后是一个 Activity MainActivity 来测试基本功能

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val db = Room.databaseBuilder(applicationContext,MyDatabase::class.java,"mydb")
            .allowMainThreadQueries()
            .build()
        val dao = db.getAllDoa()
        clearAllTables(dao)
        dao.insertWorkSpace(WorkSpace(1,"WorkSpace 1"))
        dao.insertWorkSpace( WorkSpace(2,"WorkSpace 2"))

        dao.insertWidget(Widget(1,"Widget 1"))
        dao.insertWidget(Widget(2,"Widget 2"))

        dao.insertFeed(Feed(1,"Feed 1"))
        dao.insertFeed( Feed(2,"Feed 2"))

        dao.insertWorkSpaceWidgetFeedMap(WorkSpaceWidgetFeedIntersectionMap(1,1,2))
        dao.insertWorkSpaceWidgetFeedMap(WorkSpaceWidgetFeedIntersectionMap(1,1))
        dao.insertWorkSpaceWidgetFeedMap(WorkSpaceWidgetFeedIntersectionMap(2,2))
        dao.insertWorkSpaceWidgetFeedMap(WorkSpaceWidgetFeedIntersectionMap(2,2,1))

        val wwfiList = dao.getWorkSpaceWidgetFeedIntersections()
        for(cwwfi: WorkSpaceWidgetFeedIntersectionMap in wwfiList) {
            Log.d("WWFIINFO","WorkSpaceID = " + cwwfi.workSpaceId_map + " WidgetID = " + cwwfi.widgetId_map + " FeedID = " + cwwfi.feedId_map)
        }

    }

    private fun clearAllTables(dao: AllDao) {
        dao.clearWorkSpaceWidgetFeedMap()
        dao.clearFeedTable()
        dao.clearWidgetTable()
        dao.clearWorkSpaceTable()
    }
}

获取构建的数据库（为了方便和简洁，允许在主线程上运行）
得到道
清除所有表（使测试可重新运行）
添加了 2 个工作区、2 个小部件和 2 个源
添加交叉点地图条目
提取并记录交叉点

结果

运行上面的结果：-

2021-04-04 08:31:02.942 D/WWFIINFO: WorkSpaceID = 1 WidgetID = 1 FeedID = 2
2021-04-04 08:31:02.942 D/WWFIINFO: WorkSpaceID = 1 WidgetID = 1 FeedID = 1
2021-04-04 08:31:02.942 D/WWFIINFO: WorkSpaceID = 2 WidgetID = 1 FeedID = 2
2021-04-04 08:31:02.943 D/WWFIINFO: WorkSpaceID = 2 WidgetID = 2 FeedID = 1

然后，您可以轻松地从检索到的 WorkSpaceWidgetFeedIntersectionMap 中获取相应的 WorkSpace、Wdiget 和 Feed。
查看其他内容

附加

现在要获得您的 MergedData（等价物），然后考虑对上述内容添加以下内容

新数据类IntersectionWithWorkSpaceWidgetFeed

class IntersectionWithWorkSpaceWidgetFeed(
    @Embedded
    val workSpace: WorkSpace,@Embedded
    val widget: Widget,@Embedded
    val feed: Feed
)

一个额外的 Dao 函数 getWorkSpaceWidgetAndFeedFromIntersectionMap()

@Query("SELECT * FROM workspace_widget_feed_mapping_table JOIN workspace_table ON workSpaceId = workSpaceId_map JOIN widget_table ON widgetId = widgetId_map JOIN feed_table ON feedId = feedId_map")
fun getWorkSpaceWidgetAndFeedFromIntersectionMap(): List<IntersectionWithWorkSpaceWidgetFeed>

MainActivity 的 onCreate 方法中的新（或替换现有的 6.）部分

    val iwwfList= dao.getWorkSpaceWidgetAndFeedFromIntersectionMap()
    for(iwwf: IntersectionWithWorkSpaceWidgetFeed in iwwfList) {
        Log.d("WWFINFO","WorkSpaceID = " + iwwf.workSpace.workSpaceId + " WorkSpaceName = " + iwwf.workSpace.workPlaceName +
                " WidgetID = " + iwwf.widget.widgetId + " WidgetName = " + iwwf.widget.widgetName +
                " FeedID = " + iwwf.feed.feedId + " FeedName = " + iwwf.feed.feedName
        )
    }

以上变化的结果：-

2021-04-04 09:20:34.371 D/WWFINFO: WorkSpaceID = 1 WorkSpaceName = WorkSpace 1 WidgetID = 1 WidgetName = Widget 1 FeedID = 2 FeedName = Feed 2
2021-04-04 09:20:34.371 D/WWFINFO: WorkSpaceID = 1 WorkSpaceName = WorkSpace 1 WidgetID = 1 WidgetName = Widget 1 FeedID = 1 FeedName = Feed 1
2021-04-04 09:20:34.371 D/WWFINFO: WorkSpaceID = 2 WorkSpaceName = WorkSpace 2 WidgetID = 1 WidgetName = Widget 1 FeedID = 2 FeedName = Feed 2
2021-04-04 09:20:34.371 D/WWFINFO: WorkSpaceID = 2 WorkSpaceName = WorkSpace 2 WidgetID = 2 WidgetName = Widget 2 FeedID = 1 FeedName = Feed 1

3路交叉表在房间Android

如何解决3路交叉表在房间Android

解决方法

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