如何使用 Flutter 中的 UserID 从 Firebase Firestore 检索数据？

Question

我想在每次用户登录时从 firebase firestore 中检索 userName。所以我不想使用来自 firebase 的用户 ID 检索用户数据并显示它。

我在下面附上了我当前的代码。

如何调整以下代码以使用 user_ID 作为主键从 firestore 获取 userName？

当前代码：

类 GetUserName 扩展 StatelessWidget {

  final String documentId;

  GetUserName(this.documentId);

  @override
  Widget build(BuildContext context) {
    CollectionReference users = FirebaseFirestore.instance.collection('users');

    return FutureBuilder<DocumentSnapshot>(
      future: users.doc(documentId).get(),
      builder:
          (BuildContext context, AsyncSnapshot<DocumentSnapshot> 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) {
          Map<String, dynamic> data =
              snapshot.data!.data() as Map<String, dynamic>;
          return Text("Hello, ${data['userName']}");
        }

        return Text("loading");
      },
    );
  }
}

提前谢谢你:)

Answer 1

你会想在 `` 上使用StreamBuilder 来处理当前用户，如下所示：

return StreamBuilder(
  stream: FirebaseAuth.instance.authStateChanges(),
  builder: (context, snapshot) {
    if (snapshot.connectionState != ConnectionState.active) {
      return Center(child: CircularProgressIndicator()); // ? user is loading
    }
    final user = snapshot.data;
    final uid = user.uid; // ? get the UID
    if (user != null) {
      print(user);

      CollectionReference users = FirebaseFirestore.instance.collection('users');

      return FutureBuilder<DocumentSnapshot>(
        future: users.doc(uid).get(),
        builder:
            (BuildContext context, AsyncSnapshot<DocumentSnapshot> 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) {
            Map<String, dynamic> data = snapshot.data!.data() as Map<String, dynamic>;
            return Text("Hello, ${data['userName']}");
          }

          return Text("loading");
        },
      );
    } else {
      return Text("user is not logged in");
    }
  },

在做这样的事情时，我总是把 FlutterFire 文档放在手边