在roomdb android 中面临@Relation 的问题

Question

 public class StockRelation extends Item {
        @Relation(parentColumn = "mpc", entityColumn = "itempc", entity = Location.class)
        public List<Location> locationList;
    }

    public class RStockRelation extends StockRelation{
       @Relation(parentColumn = "mpc", entityColumn = "location_itemid", entity = Location.class)
       public List<Location> locationList;
    }

here only the @Relation is getting change whereas the other things are the same. and I want to do a sort order for locationlist based on a column in the Location table in the query itself. So how to have final data in one object instead of two different StockRelation and RStockRelation. Is there any other way I can fix this

Answer 1

As I understood you have two tables (entities) and in general you want apply two left joins from first table to the second one on different fields - to get in result your first object with connected two different location lists (but use Room-Relation annotation instead of left joins).

If it's what you want, try this:

public class StockRelation extends Item {
@Relation(parentColumn = "mpc", entityColumn = "itempc", entity = Location.class)
public List<Location> locationList1;
@Relation(parentColumn = "mpc", entityColumn = "location_itemid", entity = Location.class)
public List<Location> locationList2;
}