How to retrieve data form Firestore before build flutter? - firebase

Question

I am trying get User Name through a document stored in users collection in cloud firestore but my build method runs before the data is received.
The initState(){} method does not wait for uidDetails() to complete and therefore null values are passed in DoctorListStream(currentUserName) . Since the initState(){}` method cannot be made async I want to know what can be done to fix this. I have also tried to implement both StreamBuilder and FutureBuilder but failed.
import 'package:flutter/material.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:firebase_auth/firebase_auth.dart';
import '../components/doc_list_retriever.dart';
class ListOfDoctors extends StatefulWidget {
#override
_ListOfDoctorsState createState() => _ListOfDoctorsState();
}
class _ListOfDoctorsState extends State<ListOfDoctors> {
final _auth = FirebaseAuth.instance;
final _fStore = Firestore.instance;
String currentUserUid;
String currentUserName;
#override
void initState() {
// TODO: implement initState
super.initState();
uidDetails();
}
void uidDetails() async {
final FirebaseUser user = await _auth.currentUser();
currentUserUid = user.uid;
print(currentUserUid + 'from user details');
await Firestore.instance
.collection('users')
.document(currentUserUid)
.get()
.then((DocumentSnapshot) {
currentUserName = DocumentSnapshot.data['name'].toString();
});
print(currentUserName + ' from uid Details');
}
#override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: Color(0xFF1D1E33),
body: SafeArea(
child: Column(
children: <Widget>[
Text(
'Doctors:',
textAlign: TextAlign.left,
style: TextStyle(fontSize: 40, color: Colors.white70),
),
DoctorListStream(currentUserName),
],
),
),
);
}
}
CONSOLE :
Performing hot restart...
Syncing files to device AOSP on IA Emulator...
Restarted application in 848ms.
I/BiChannelGoogleApi(27263): [FirebaseAuth: ] getGoogleApiForMethod() returned Gms: com.google.firebase.auth.api.internal.zzaq#95a83d7
D/FirebaseAuth(27263): Notifying id token listeners about user ( 5TlH5zoCqfWDNDlAgvIsc5yAHPA3 ).
I/flutter (27263): 5TlH5zoCqfWDNDlAgvIsc5yAHPA3from user details
════════ Exception caught by widgets library ═══════════════════════════════════════════════════════
The following NoSuchMethodError was thrown building StreamBuilder<QuerySnapshot>(dirty, state: _StreamBuilderBaseState<QuerySnapshot, AsyncSnapshot<QuerySnapshot>>#044e7):
The method '+' was called on null.
Receiver: null
Tried calling: +(" from doctor list stream")
The relevant error-causing widget was:
StreamBuilder<QuerySnapshot> file:///D:/projects/clinic/lib/components/doc_list_retriever.dart:14:12
When the exception was thrown, this was the stack:
#0 Object.noSuchMethod (dart:core-patch/object_patch.dart:53:5)
#1 DoctorListStream.build.<anonymous closure> (package:clinic/components/doc_list_retriever.dart:26:27)
#2 StreamBuilder.build (package:flutter/src/widgets/async.dart:509:81)
#3 _StreamBuilderBaseState.build (package:flutter/src/widgets/async.dart:127:48)
#4 StatefulElement.build (package:flutter/src/widgets/framework.dart:4623:28)
...
════════════════════════════════════════════════════════════════════════════════════════════════════
I/flutter (27263): Dhruv from uid Details
════════ Exception caught by rendering library ═════════════════════════════════════════════════════
A RenderFlex overflowed by 99670 pixels on the bottom.
The relevant error-causing widget was:
Column file:///D:/projects/clinic/lib/screens/list_of_doctors.dart:43:16
════════════════════════════════════════════════════════════════════════════════════════════════════

Answer 1

I would opt to using a stream builder to get the user data. sample implementation
String username;
body: StreamBuilder(
stream: Firestore.instance
.collection('users')
.document(userid)
.snapshots(),
builder: (context, snapshot) {
if (!snapshot.hasData) {
return SpinKitDoubleBounce(
color: Colors.blue,
);
}
var userDoc = snapshot.data;
userName = userDoc["name"];
return .... //your other widgets