flutter - 无法检查用户帐户是否存在？

Question

Helo，我正在尝试检查用户的帐户是否存在，如果不存在，我要运行“帐户已删除”文本。
但是问题是，当我启动该应用程序时，屏幕上会显示现有帐户，只有重置后我才能获得真实的结果。
好像是在第一次运行应用程序后完成了帐户检查，但是我不知道哪里出了错。
这是代码，在此先感谢您:

class CheckIfDeletedAccount extends StatelessWidget {
  String isAccountDeleted;

  getData() async {
    var userType = await Firestore.instance
        .collection('users')
        .where('userEmail', isEqualTo: email)
        .getDocuments();
    userType.documents.forEach((result) {
      log(result.data["deleted"]);
      isAccountDeleted = result.data["deleted"].toString();
    });
  }

  @override
  Widget build(BuildContext context) {
    getData();
    //log(isAccountDeleted);
    if (isAccountDeleted == "true") {
      return Scaffold(
        body: Container(
          child: Center(
            child: Text("account is deleted"),
          ),
        ),
      );
    }
    return MaterialApp(
      theme: themeData,
      home: Scaffold(
        body: Bar(),
      ),
    );
  }
}

Answer 1

您需要等待Firebase的结果。您正在尝试在初始化isAccountDeleted之前构建窗口小部件。
在您的方案中，可以按以下方式使用FutureBuilder:

class CheckIfDeletedAccount extends StatelessWidget {
  String isAccountDeleted;

  Future<String> getData() async {
    var userType = await Firestore.instance
        .collection('users')
        .where('userEmail', isEqualTo: email)
        .getDocuments();
    userType.documents.forEach((result) {
      log(result.data["deleted"]);
      isAccountDeleted = result.data["deleted"].toString();
    });
    return isAccountDeleted;
  }

  @override
  Widget build(BuildContext context) {
    return FutureBuilder(
    future: getData(),
    builder: (BuildContext context, AsyncSnapshot snapshot) {
    if(snapshot.connectionState == ConnectionState.done &&
         snapshot.hasData) {
        final isAccountDeleted = snapshot.data;

        if (isAccountDeleted == "true") {
          return Scaffold(
            body: Container(
              child: Center(
                child: Text("account is deleted"),
              ),
            ),
          );
        }

        return MaterialApp(
          theme: themeData,
          home: Scaffold(
            body: Bar(),
          ),
        );
    }
      return Center(child: const CircularProgressIndicator());
      },
    );
  }
}