如何在 flutter 列表视图和 firebase 中动态更改值

Question

由于所有文档上的 for 循环，我正在递增整个列表，但无法解决如何 increment/decrement 特定索引，请告诉我该怎么做。我在 streame 构建器和列表视图构建器中有以下代码。

Column(
    mainAxisAlignment: MainAxisAlignment.center,
    children: [
      InkWell(
        onTap: () async {
          final QuerySnapshot result =
              await FirebaseFirestore.instance
                  .collection('mynamazstatus')
                  .get();
          final List<DocumentSnapshot> documents =
              result.docs;
          // ignore: avoid_print
          for (var data in documents) {
            FirebaseFirestore.instance
                .collection('mynamazstatus')
                .doc(data.id)
                .update({
              praises['count']: FieldValue.increment(1)
            });
          }
        },
        child: const Icon(
          Icons.arrow_drop_up,
          size: 20,
        ),
      ),
      InkWell(
        onTap: () async {
          final QuerySnapshot result =
              await FirebaseFirestore.instance
                  .collection('mynamazstatus')
                  .get();
          final List<DocumentSnapshot> documents =
              result.docs;
          // ignore: avoid_print
          for (var data in documents) {
            FirebaseFirestore.instance
                .collection('mynamazstatus')
                .doc(data.id)
                .update({
              praises['count']: FieldValue.increment(-1)
            });
          }
          },
        child: const Icon(
          Icons.arrow_drop_down,
          size: 20,
        ),
      ),
    ],
  ),

它适用于应用程序 UI 以及 firebase，但对于所有文档，只需轻轻一按。

Answer 1

您可以直接将一个名为 index 的字段添加到您的文档中，并将其用作引用以获取与该索引匹配的文档。假设您在从 StreamBuilder 小部件，如：

StreamBuilder(
     stream: FirebaseFirestore.instance.collection('mynamazstatus').snapshots(),
     builder: (context, snapshot) {
        
       if (snapshot.hasData) {
         List<DocumentSnapshot> docs = (snapshot.data! as QuerySnapshot).docs;

         // return your documents in a list, for example
         return ListView.builder(
            itemCount: docs.length,
            itemBuilder: (context, index) {
               // ... use this index to both pull the document and to save to it as well

              DocumentSnapshot docRef = docs.where((d) => d.data()['index'] == index).first;

              // now, use the docRef to render your components, as well as
              // hook it up to the InkWell

            }
         )
       }

       return Center(child: CircularProgressIndicator());
   }
)

然后当您在 ListView.builder 中构建小部件时，使用 [=16] 对获取的 DocumentSnapshot 的引用=]index (docRef) 你可以这样更新它：

InkWell(
  onTap: () async {
    FirebaseFirestore.instance
      .collection('mynamazstatus')
      .doc(docRef.id)
      .update({
        praises['count']: FieldValue.increment(-1)
      });                         
  },
    child: const Icon(
    Icons.arrow_drop_down,
    size: 20,
  ),
)

如何在 flutter 列表视图和 firebase 中动态更改值

how to change values dynamically in a flutter list view and firebase as well

firebase

flutter

listview