Flutter Realtime数据库未显示

Question

我正在尝试从实时Firebase检索数据。没有错误显示，但屏幕上仍然没有数据显示。我正尝试将数据显示在卡片中，如下图所示：

这是我的代码：

  **List<Restaurant> restaurantsList = [];
  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    
    DatabaseReference restRef = FirebaseDatabase.instance.reference().child('restaurant');
    restRef.once().then((DataSnapshot snap){
      var keys = snap.value.keys;
      var data = snap.value;
      restaurantsList.clear();
      for(var key in keys){
        
        Restaurant rest = new Restaurant
        (
          data[key]['image'],
          data[key]['name'],
          data[key]['description'],
        );
        restaurantsList.add(rest);
      }
      setState(() {
        print('$restaurantsList');
        print('Length : $restaurantsList.length');
      });
    });
  }

  GridView.builder(
              shrinkWrap: true,
              primary: false,
              physics: NeverScrollableScrollPhysics(),
              gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
                crossAxisCount: 2,
                childAspectRatio: MediaQuery.of(context).size.width /
                    (MediaQuery.of(context).size.height / 1.25),
              ),
              itemCount: restaurantsList == null ? 0 :restaurantsList.length,
              itemBuilder: (BuildContext context, int index) {
                return GridProduct(
                  img: restaurantsList[index].image,
                  isFav: false,
                  name: restaurantsList[index].name,
                  rating: 5.0,
                  raters: 23,
                );
              },
            ),