I've been stuck for several hours with a problem on flutter. If you can help me that would be really nice.

I need to put "await" in my Widget build(BuildContext context){} but it's impossible to put "async". How to do ?

When i test void _myAsyncMethod()async{} :

CodePudding user response：

To Fix your issue you can put async in the body of method like this

Before=> Widget build(BuildContext context) {

   

After=> Widget build(BuildContext context) async{

Although this will not solve your problem as flutter wiill warn you as this is not the proper way to do it.

It's not a good practice to call await inside flutter's build method Because

1. Generally an apps need to run a 60 frames per second on an average hence flutter's build method we'll be called over and over to re-render the ui.
2. Another reason is that, doing calling await function() in build method will block your UI.

Solution

1. use FutureBuilder
2. call await auth.currentUser() in initState method

Another way to solve this is to use FutureBuilder

sample Code for 1

FutureBuilder(
      builder: (BuildContext ctx, AsyncSnapshot<userModel> snapshot) {
        if(ConnectionState.done == snapshot.connectionState) {
          return Text(snapshot.data.userId);
        } else {
          return CircularProgressIndicator();
        }
      },
      future: auth.currentUser(),
    );

sample Code for 2(stateful widget)

late UserModel;   
void initState() {
 UserModel user = await auth.currentUser();   
}

this is very basic code but it's enough for you to get started.

Note: I've assumed userModel mentioned above is response type of auth.currentUser() you can change it accordingly.

CodePudding user response：

What you want to do is not optimal but you can create a method and put your await variable in there:

 late final FirebaseUser _user;
  void _myAsyncMethod()async{
    _user = await auth.currentUser;
  }

  @override
  Widget build(BuildContext context) {
    _myAsyncMethod();
    return Scaffold(appBar: AppBar(), body: Container());
  }

CodePudding user response：

1. If your are using stateful widget you can instantiate firebase auth in initstate() method.

class testFirless extends StatefulWidget {
  var currentuseid = "";

  testFirless({Key? key}) : super(key: key);

  @override
  _testFirlessState createState() => _testFirlessState();
}
class _testFirlessState extends State<testFirless> {
  @override
  Widget build(BuildContext context) {
    return Container();
  }

  // ------------------------------------>heree
  @override
  Future<void> initState() async {
    FirebaseAuth auth = FirebaseAuth.instance;

    var user = await auth.currentUser;
    if (user == null) {
      widget.currentuseid = user!.uid;
    } else {
      print('User is signed in!');
    }
  }
}

2. FutureBuilder

class fbuilder extends StatelessWidget {
  const fbauth({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    FirebaseAuth auth = FirebaseAuth.instance;


// --------------->
    return Container(child: FutureBuilder(
      builder: (BuildContext ctx, AsyncSnapshot<User> snapshot) {
        if (ConnectionState.done == snapshot.connectionState) {
          return Text(snapshot.data.userId.toString());
        } else {
          return CircularProgressIndicator();
        }
      },
      future: auth.currentUser(),
    ));
  }
}

3. in stateless or stateful widget

String currentuseid="";
        class fbauth extends StatelessWidget {
          const fbauth({Key? key}) : super(key: key);
        
          @override
          Widget build(BuildContext context) {
         
       FirebaseAuth auth = FirebaseAuth.instance;
 //   ------------------------>    
            auth.currentUser().then((user) {
              if (user == null) {
                currentuseid = user!.uid;
              } else {
                print('User is signed in!');
              }
              // other logic after the user retrieval
            });
        
            return Container();
          }
}

Nb: Instead of instantiating firebase auth in every widget .you must instantiate in `void main` method