Android with Room - How to set a foreign key nullable - android-sqlite

Question

I'm using Room in my Android app. One table (stock_move) contains several Foreign keys. In some case, I need to insert a stock_move without a FK (locationDestId). In this case, SQLite raise an error:
io.reactivex.exceptions.OnErrorNotImplementedException: foreign key constraint failed (code 19)
There is my entity:
#Entity(tableName = "stock_move",
foreignKeys = {
#ForeignKey(
entity = LocationEntity.class,
parentColumns = "id",
childColumns = "location_id",
onDelete = CASCADE
),
#ForeignKey(
entity = LocationEntity.class,
parentColumns = "id",
childColumns = "location_dest_id",
onDelete = CASCADE
),
#ForeignKey(
entity = ProductEntity.class,
parentColumns = "id",
childColumns = "product_id",
onDelete = CASCADE
),
#ForeignKey(
entity = UomEntity.class,
parentColumns = "id",
childColumns = "uom_id",
onDelete = CASCADE
)
}
)
public class StockMoveEntity {
#PrimaryKey(autoGenerate = true)
private int id;
private String name;
#ColumnInfo(name="product_id")
private int mProductId;
#ColumnInfo(name="uom_id")
private int mUomId;
#ColumnInfo(name="location_id")
private int mLocationId;
#ColumnInfo(name="location_dest_id")
private int mLocationDestId;
private int mProductQty;
public StockMoveEntity(int id, String name, int productId, int uomId, int locationId, int locationDestId, int productQty) {
this.id = id;
this.name = name;
mProductId = productId;
mUomId = uomId;
mLocationId = locationId;
mLocationDestId = locationDestId;
mProductQty = productQty;
}
}

Answer 1

If you change the data type for the mLocationDestId variable from int to Integer the schema should be generated without the NOT NULL constraint for your location_dest_id column since Integer is nullable.
I've only tested this with version 1.1.0-alpha3 of room so I don't know if it works with 1.0.0 as well.