颤振中的流生成器​​返回空值

Question

我在我的应用程序中使用流构建器，但它一直返回 null

  MyUserClass? user = Provider.of<MyUserClass?>(context);
    print('$user settings_form \n ${user!.uid}');

    return StreamBuilder<UserData?>(
      stream: DatabaseService(uid: user.uid).userData,
      builder: (context, snapshot) {
        if(snapshot.hasData){
            UserData? userData = snapshot.data;

            return Form(
              key: _formKey,
              child: Column(
                children: <Widget>[
                  Text(
                    'Update your brew settings',
                    style: TextStyle(fontSize: 18),

                  ),
                  SizedBox(height: 20,),
                  TextFormField(
                    initialValue: userData!.name,
                    decoration: textInputDecoration,
                    validator: (val) =>
                    val!.isEmpty
                        ? 'Please enter name'
                        : null,
                    onChanged: (val) => setState(() => _currentName = val),
                  ),
                  SizedBox(height: 20,),                       
               style: ElevatedButton.styleFrom(
                        primary: Colors.pink
                    ),
                  )
                ],
              ),
            );

        } else{
          return Loading();
        }

我想从我的类“MyUserClass”中获取用户信息，用户信息正在控制台中打印信息，但它返回空值。