房间 Android 中的 3 路交叉口 Table

Question

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 table 是下面的 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关系当三个 table 都参与时，他们应该聚在一起

我阅读了指南 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我什至无法用它构建那些

我尝试使用 Workspace 和 Widget 一对多，使用 Widget 和 Feed 尝试多对多然后我在我的工作区中获取我不想要的小部件的提要。

在这一点上我真的很困惑任何朝着正确方向的推动将不胜感激

更新

根据下面迈克的回答，我得到了这个

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, associatedUserId=test, 
workSpaceName=Demo),
 widget=WidgetMetaData(widgetId=12, widgetName=Widget2, backgroundColor=None, widgetType=normal, dataUrl=www), 
feed=Feed(feedId=1, feedName=Feed1, count=2, asyncInterval=1234)),
 IntersectionWithWorkSpaceWidgetFeed(workSpace=WorkSpace(workSpaceId=2, associatedUserId=igvuser, workSpaceName=Demo),
 widget=WidgetMetaData(widgetId=13, widgetName=Widget3, backgroundColor=None, widgetType=normal, dataUrl=www),
 feed=Feed(feedId=2, feedName=Feed2, count=0, asyncInterval=1234))]

足够接近我原来的 MergedData POJO。谢谢迈克。

Answer 1

我相信您想要 3 向映射 table。每行由 3 列组成，WorkSpaceId、WidgetId 和 FeedId，主键由所有 3 列组成。

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
)

小部件

@Entity(
    tableName = "widget_table",

)
data class Widget(
    @PrimaryKey
    val widgetId:Long,
    val widgetName: String
)

供稿

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

新映射tableWorkSpaceWidgetFeedIntersectionMap

@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>

}

数据库我的数据库

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

最后 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(1,1,1))
        dao.insertWorkSpaceWidgetFeedMap(WorkSpaceWidgetFeedIntersectionMap(2,1,2))
        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）
得道
清除所有 tables（使测试重新运行可用）
添加 2 个 WorkSpaces、2 个小部件和 2 个提要
添加交叉路口地图条目
提取并记录交叉点

结果

运行以上产生：-

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。
查看附加信息

额外

现在获取 MergedData（等效），然后考虑对上述内容进行以下添加

新数据classIntersectionWithWorkSpaceWidgetFeed

:-

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 方法中的一个新的（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
        )
    }

上述更改的结果：-

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

房间 Android 中的 3 路交叉口 Table

3 way intersection Table in room Android

sqlite

android

relational-database

android-room