Stream Initial state is ConnectionState.waiting instead of null - firebase

Question

import 'dart:async';
import 'package:flutter/material.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:google_sign_in/google_sign_in.dart';
final FirebaseAuth _auth = FirebaseAuth.instance;
final GoogleSignIn _googleSignIn = new GoogleSignIn();
class HomePage extends StatefulWidget {
static String tag = 'home-page';
#override
HomePageState createState() {
return new HomePageState();
}
}
class HomePageState extends State<HomePage> {
Stream<FirebaseUser> _currentUser;
Future<FirebaseUser> signInWithGoogle() async {
print('google signin invoked');
GoogleSignInAccount googleUser = await _googleSignIn.signIn();
GoogleSignInAuthentication googleAuth = await googleUser.authentication;
FirebaseUser user = await _auth.signInWithGoogle(
accessToken: googleAuth.accessToken,
idToken: googleAuth.idToken,
);
print("signed in " + user.displayName);
return user;
}
#override
Widget build(BuildContext context) {
final lblWelcome = Padding(
padding: EdgeInsets.all(8.0),
child: Text('Frnds Payment',
style: TextStyle(fontSize: 28.0, color: Colors.green)));
final btnSignin = new MaterialButton(
child: const Text('Sign In with Google'),
onPressed: () {
print('button clicked');
_currentUser = signInWithGoogle()?.asStream();
});
final txtOutput = new StreamBuilder<FirebaseUser>(
stream: _currentUser,
builder: (BuildContext context, AsyncSnapshot<FirebaseUser> snapshot) {
switch (snapshot.connectionState) {
case ConnectionState.none:
case ConnectionState.waiting:
return new Center(child: new CircularProgressIndicator());
default:
if (snapshot.hasError)
return new Text('Error: ${snapshot.error}');
else
return new Center(
child: new Text('${snapshot.data.displayName}'));
}
});
final body = Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[lblWelcome, btnSignin, txtOutput],
),
);
return Scaffold(body: body);
}
}
I am newbee to Dart, this is my 1st app.
I need to display the Username after the signin is succesful.
Whenever I start the application it goes to ConnectionState.waiting instead of ConnectionState.none.
Also it does not render the textbox with displayname on succesful signin. reloading it does render the display name.

Answer 1

ConnectionState.none means there is no stream assigned,
but you have
setState(() => _currentUser = signInWithGoogle()?.asStream());
this means the StreamBuilder subscribed to this stream and waits for events.