错误：await 表达式只能在异步函数中使用。尝试用“async”或“async*”标记函数体

Question

class Wrapper extends StatelessWidget {
  @override
  Widget build(BuildContext context) {

    final user = Provider.of<User>(context);
    DocumentSnapshot snapShot = await Firestore.instance.collection('members').document(user.uid).get(); //re

    //defining the user id
    List<String> hr = [
      "4xldjjaJKBOppV0ioZLaIekVNdr1",  //shreya shreya.21810101@viit.ac.in
      "20D18eFrsnRNmbtVnnvq8U0ZW1s2"   //pranav pranav.21810339@viit.ac.in
    ];
    List<String> doc = [
      "3DoGWLpamEVwXyT57hCyybkGIkc2",  //harsha harsha.21810512@viit.ac.in
      "YBHsJC5W6IYa1qfdIaXAwbvKKOG2",  //saampatii saampatii.21810826@viit.ac.in
    ];
    List<String> gs = [
      "5QCDzv1YjQhQdLORJ7CthfATeHt1"   //digu digvijay.21810245@viit.ac.in
    ];


    if(user == null){
      return Authenticate();
    }else if(snapShot == null || !snapShot.exists){return MemberData();}
    else{
      if(user.uid == hr[0]){return Hr();}
      else if(user.uid == hr[1]){return Hr();}
      else if(user.uid == doc[0]){return Doc();}
      else if(user.uid == doc[1]){return Doc();}
      else if(user.uid == gs[0]){return Gs();}
      else{return Home();}
    }
  }
}

我可以做些什么来消除错误？

在那里，我尝试检查具有该 uid 的文档是否存储在我的 Firestore 中。有没有其他方法不报错？

Answer 1

要使用 await，你必须让你的函数异步：

Future<Widget> getData(user) async {
  DocumentSnapshot snapShot = await Firestore.instance.collection('members')
                                                      .document(user.uid).get();
  //defining the user id
    List<String> hr = [
      "4xldjjaJKBOppV0ioZLaIekVNdr1",  //shreya shreya.21810101@viit.ac.in
      "20D18eFrsnRNmbtVnnvq8U0ZW1s2"   //pranav pranav.21810339@viit.ac.in
    ];
    List<String> doc = [
      "3DoGWLpamEVwXyT57hCyybkGIkc2",  //harsha harsha.21810512@viit.ac.in
      "YBHsJC5W6IYa1qfdIaXAwbvKKOG2",  //saampatii saampatii.21810826@viit.ac.in
    ];
    List<String> gs = [
      "5QCDzv1YjQhQdLORJ7CthfATeHt1"   //digu digvijay.21810245@viit.ac.in
    ];


    if(user == null){
      return Authenticate();
    }else if(snapShot == null || !snapShot.exists){return MemberData();}
    else{
      if(user.uid == hr[0]){return Hr();}
      else if(user.uid == hr[1]){return Hr();}
      else if(user.uid == doc[0]){return Doc();}
      else if(user.uid == doc[1]){return Doc();}
      else if(user.uid == gs[0]){return Gs();}
      return Home();
    }

}