无法从 Firebase 数据库中获取数据

Question

我已经这样做了，但它对我说 class bool has no instance method [] reciver null tried 调用 []ok

class Test7 extends StatefulWidget {
  @override
  _Test7State createState() => _Test7State();
}

class _Test7State extends State<Test7> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.deepPurple,
      appBar: AppBar(),
      body:  SingleChildScrollView(
        child: Flexible(
          child: FirebaseAnimatedList(
            shrinkWrap: true,
            query: FirebaseDatabase.instance.reference().child(currentUser.uid), // when i remove child(currentUser.uid)it is work !
            itemBuilder: (BuildContext context, DataSnapshot snapshot,Animation<double> animation,  int index) {
              return ListTile(
                leading: IconButton(
                  onPressed: () {  },
                  icon: Icon(Icons.ac_unit),
                ),
                title: Text(snapshot.value["ok"]),
              );
            },),
        ),
      ),
    );
  }
}

我在 Firebase 数据库中实时拥有这个

    NUuhYzfVS9YPYDIox3X6ozhzFiT2
activity: true
ok: "ok"

Answer 1

A FirebaseAnimatedList 显示您在query 中指定的数据库路径下的子节点列表。如果您在该路径中指定 UID，您最终会得到这两个子节点：

activity: true
ok: "ok"

所以您的 itemBuilder 被调用了两次：一次是 activity: true，一次是 ok: "ok"。然后当你在 snapshot 上调用 snapshot.value["ok"] 时，就没有这样的 child 属性了。

底线：FirebaseAnimatedList 只有在显示用户列表时才有意义。当您显示特定用户时，您不能在 FirebaseAnimatedList 中显示它，您通常希望在 Text 小部件中显示它，使用（例如）FutureBuilder:

FutureBuilder(
  future: FirebaseDatabase.instance.reference().child(currentUser.uid).get(),
  builder:
      (BuildContext context, AsyncSnapshot snapshot) {

    if (snapshot.hasError) {
      return Text("Something went wrong");
    }

    if (snapshot.hasData && !snapshot.data!.exists) {
      return Text("Document does not exist");
    }

    if (snapshot.connectionState == ConnectionState.done) {
      return Text(snapshot.data.value["ok"]);
    }

    return Text("loading");
  },

无法从 Firebase 数据库中获取数据

cannot fetch data from Firebase database

zip

dart

firebase-realtime-database

flutter