MultiSelection查询Firestore文档

Question

我只需要根据“多项选择”来过滤和查询在“列表”图块列表中选择的Firestore文档。

我当前的选择是将查询与所选选项上的功能是否等于Firestore中的可用数据一起使用。

getFoods(FoodNotifier foodNotifier) async {

var query =  Firestore.instance
      .collection('Foods')
      .orderBy('create at', descending: true);
      
if (food.newcategory !=  widget.favoriteCategory[index].isSelected) {
    query = query.where("name", isEqualTo: food.name);
}
      QuerySnapshot snapshot = await query.getDocuments();

      
      List<Food> _foodList = [];
    
      snapshot.documents.forEach((document) {
        Food food = Food.fromMap(document.data);
      
        _foodList.add(food);
    });
  foodNotifier.foodList = _foodList;
}

我要针对下面的类中提到的一种特定类别过滤列表视图的数据，但是它无法正常工作。

class FoodChoice{
  FoodChoice(this.newcategory);

  String newcategory;
  bool isSelected=false;

  FoodChoice.fromMap(Map<String, dynamic> data)  {
  newcategory = data['newcategory'];
  }
}

  List<FoodChoice> favoriteCategory;

  Selection(this.favoriteCategory);

  @override
  _SelectionState createState() => _SelectionState();
}

class _SelectionState extends State<Selection> {


  @override
  Widget build(BuildContext context) {
    return ListView.builder(
      itemBuilder: (ctx, index) {
        return GestureDetector(
          behavior: HitTestBehavior.opaque,
          onTap: () {
            widget.favoriteCategory[index].isSelected = !widget.favoriteCategory[index].isSelected;
            setState(() {});
          },
          child: Container(
            color: widget.favoriteCategory[index].isSelected
                ? Colors.green[100]
                : null,
            child: Row(
              children: <Widget>[
                Checkbox(
                    value: widget.favoriteCategory[index].isSelected,
                    onChanged: (s) {
                      widget.favoriteCategory[index].isSelected = !widget.favoriteCategory[index].isSelected;
                      setState(() {});
                    }),
                Text(widget.favoriteCategory[index].newcategory)
              ],
            ),
          ),
        );
      },
      itemCount: widget.favoriteCategory.length,
    );
  }
}

第二个选项是将选择/过滤器直接集成到同样无法正常工作的StreamBuilder中。

class Feed extends StatefulWidget {
  @override
  _FeedState createState() => _FeedState();
}

class _FeedState extends State<Feed> {
  final Set<BuildContext> _saved = new Set<BuildContext>();


  @override
  void initState() {
    FoodNotifier foodNotifier = Provider.of<FoodNotifier>(context, listen: false);
    getFoods(foodNotifier);
    super.initState();
  }

  @override
  Widget build(BuildContext context, {Widget leading, IconData trialing: Icons.keyboard_arrow_right}) {
    FoodNotifier foodNotifier = Provider.of<FoodNotifier>(context);
    final bool alreadySaved = _saved.contains(context);
    final List<FoodChoice> favoriteCategory;
    final int index;
//    Future<void> _refreshList() async {
//      getFoods(foodNotifier);
//    }






    print("building Feed");

    return Scaffold(
      body:StreamBuilder<QuerySnapshot>(
        stream: Firestore.instance.collection("Products").where('newcategory',isEqualTo: favoriteCategory[index]['product_id'].snapshots(),
        builder: (context, snapshot) {
          return !snapshot.hasData
              ? Center(child: CircularProgressIndicator())
              : ListView.separated(
          itemBuilder: (BuildContext context, int index) {
            return ListTile(
              leading: Image.network(
                foodNotifier.foodList[index].image != null
                    ? foodNotifier.foodList[index].image
                    : 'https://www.testingxperts.com/wp-content/uploads/2019/02/placeholder-img.jpg',
                width: 120,
                fit: BoxFit.fitWidth,
              ),
              title: Text(foodNotifier.foodList[index].name),
              subtitle: Text(foodNotifier.foodList[index].category),
              trailing: new Icon(   // Add the lines from here... 
              alreadySaved ? Icons.favorite : Icons.favorite_border,
              color: alreadySaved ? Colors.red : null,
              ),
              onTap: () async {
                await new Future.delayed(const Duration(seconds: 1));
                foodNotifier.currentFood = foodNotifier.foodList[index];
                Navigator.of(context).push(MaterialPageRoute(builder: (BuildContext context) {
                  return FoodDetaill();
                }));
              },
            );
          },
          itemCount: foodNotifier.foodList.length,
          separatorBuilder: (BuildContext context, int index) {
            return Divider(
              color: Colors.black,
            );
          },
        );
        }
        ),
  );
}
}

根据用户输入选择查询的最佳方法是什么？我们可以整合变量吗？我正在努力查看缺少的内容，或者在列表选择和查询之间建立链接。