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android - 颤振嵌套的火力基地

问题描述

有人能解释一下为什么这个类运行时 productlist 变量为空吗？看起来变量是在第一个实例结束后填充的，因此 CardShopList 小部件没有来自嵌套实例的产品列表。你有什么建议吗？谢谢！

  Future getMyShopLists(User user) async {
    List<Widget> listItems = [];

    FirebaseFirestore.instance
        .collection('user')
        .doc(user.uid)
        .collection('shoplist')
        .get()
        .then((event) {
      event.docs.forEach((shoplist) {
        List<ProductModel> productlist = [];
        Map shopListData = shoplist.data();

        shoplist.reference.collection('productlist').get().then((element) {
          Map productData = shoplist.data();
          element.docs.forEach((doc) {
            productlist.add(ProductModel(
              id: doc.id,
              name: productData['name'],
              quantity: productData['quantity'],
              price: productData['price'],
            ));
          });
        });

        listItems.add(CardShopList(
          shoplist.id,
          shopListData['name'],
          productlist, // <------------------------------- THIS IS NULL!!!!
          getMyShopLists,
          key: ValueKey<String>(shoplist.id),
        ));
      });
      if (this.mounted) {
        setState(() {
          shopListsWidget = listItems;
        });
      }
    });

    return shopListsWidget;
  }

编辑我在这个 FutureBuilder 中使用该类：

FutureBuilder(
            future:
                searchIcon.icon == Icons.search ? getMyShopLists(user) : null,
            builder: (BuildContext context, AsyncSnapshot snapshot) {
              if (snapshot.hasData) {
                return isShopListEmpty
                    ? new Center(
                        child: new Text(
                          "x",
                          style: TextStyle(fontSize: 20),
                          textAlign: TextAlign.center,
                        ),
                      )
                    : Container(
                        child: Column(
                          children: <Widget>[
                            Expanded(
                                child: ListView.builder(
                                    itemCount: shopListsWidget.length,
                                    physics: BouncingScrollPhysics(),
                                    itemBuilder: (context, index) {
                                      return shopListsWidget[index];
                                    }))
                          ],
                        ),
                      );
              } else {
                return Center(
                  child: CircularProgressIndicator(),
                );
              }
            },
          ),

标签： androidfirebaseflutterdartgoogle-cloud-firestore

解决方案

由于您使用的是 foreach，因此预计不会填写“产品列表”。可能有替代解决方案，但将 foreach 转向 for 可能会解决它。

 ...
   await FirebaseFirestore.instance //added await
        .collection('user')
        .doc(user.uid)
        .collection('shoplist')
        .get()
        .then((event) async{ //added async
        for(QueryDocumentSnapshot shoplist in event.docs){ //---this line changed
        List<ProductModel> productlist = [];
        Map shopListData = shoplist.data();

        await shoplist.reference.collection('productlist').get().then((element) //added await 
{
        Map productData = shoplist.data();
        for(QueryDocumentSnapshot doc in element.docs) //---this line changed
         {
            productlist.add(ProductModel(
              id: doc.id,
              name: productData['name'],
              quantity: productData['quantity'],
              price: productData['price'],
            ));
         }       
        });

        listItems.add(CardShopList(
          shoplist.id,
          shopListData['name'],
          productlist,
          getMyShopLists,
          key: ValueKey<String>(shoplist.id),
        ));
      }
     ...

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