firebase - 获得当前用户时未设置我的变量

Question

我正在使用带有dart语言的Flutter，但我已经对用户进行了Google身份验证，但我只想得到他的电子邮件以过滤其数据。

为什么在“setState”方法内部获取用户，然后currentUser再次为null？

 class ListDataState extends State<ListScreen> {

  List<Data> list;
  FirebaseUser currentUser;
  void _loadCurrentUser() async {
    FirebaseAuth.instance.currentUser().then((FirebaseUser user) {
      setState(() {
        this.currentUser = user;
        print("- user authenticated: ${currentUser.email}");
      });
    });
  }

  @override
  void initState() {
    super.initState();
    _loadCurrentUser();
    if(currentUser==null  )print("- Now my user is null");

     filterDataByUser()
  }

 void filterDataByUser(){
    if(currentUser==null  )print("- Now my user is still null");
     Stream<QuerySnapshot> querySnapshot=_db.collection("collection").where("userEmail",isEqualTo: currentUser.email)
    // adding data to list
 }

 // ... some code listing data by authenticated user ...
 }

输出:

I/flutter (24753): - user authenticated: xxx@gmail.com
I/flutter (24753): - Now my user is null
I/flutter (24753): - Now my user is still null

如果更改这部分代码，则此代码有效:

.where("userEmail",isEqualTo: currentUser.email)

通过我的电子邮件:

.where("userEmail",isEqualTo: "xxx@gmail.com")

Answer 1

_loadCurrentUser()应该是异步的，以便您在调用此代码if(currentUser==null )print("- Now my user is null");之前等待函数完成执行。

class ListDataState extends State<ListScreen> {

  FirebaseUser currentUser;
  Future _loadCurrentUser() async{
    FirebaseUser user = await FirebaseAuth.instance.currentUser();
    setState(() {
      currentUser = user;
      print("- user authenticated: ${currentUser.email}");
    });
  }

  @override
  void initState() {
    super.initState();
    filterDataByUser();
  }

  void filterDataByUser() async{
    await _loadCurrentUser();
    if(currentUser==null)print("- Now my user is null");
    if(currentUser==null)print("- Now my user is still null");
  }

// ... some code listing data by authenticated user ...
}