FutureBuilder runs twice - flutter

Question

I have problems with FutureBuilder starting twice.
First it fetch the data correctly, returning my StartScreen, then after few seconds, the StartScreen rebuilds and I noticed that the FutureBuilder fires again.
Here is my code and it's pretty simple, so I wonder what may the problem be?!?
class MyApp extends StatefulWidget {
#override
_MyAppState createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
FirebaseUser user;
#override
void initState() {
// TODO: implement initState
super.initState();
getNewestlocation();
}
#override
void dispose() {
super.dispose();
}
#override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
title: 'APP',
theme: buildTheme(),
home: FutureBuilder<FirebaseUser>(
future: Provider.of<AuthService>(context).getUser(),
builder: (context, AsyncSnapshot<FirebaseUser> snapshot) {
if (snapshot.connectionState == ConnectionState.done) {
if (snapshot.error != null) {
print('error');
return Text(snapshot.error.toString());
}
user = snapshot.data;
print('user here $user');
return snapshot.hasData ? StartScreen(user) : LoginScreen();
} else {
return LoadingCircle();
}
},
),
);
}
}
Can anyone help me with this, please?

Answer 1

The future is firing again because you're creating it in the build method at the same time as the FutureBuilder.
From the FutureBuilder docs:
The future must have been obtained earlier, e.g. during State.initState, State.didUpdateConfig, or State.didChangeDependencies. It must not be created during the State.build or StatelessWidget.build method call when constructing the FutureBuilder. If the future is created at the same time as the FutureBuilder, then every time the FutureBuilder's parent is rebuilt, the asynchronous task will be restarted.
So to prevent it from firing you'd have to do something like this:
class _MyAppState extends State<MyApp> {
Future<String> _myString;
#override
void initState() {
super.initState();
_myString = _fetchString();
}
#override
Widget build(BuildContext context) {
return Scaffold(
body: FutureBuilder(
future: _myString,
builder: (context, snapshot) {
// build page stuff...
},
),
);
}
}
Future<String> _fetchString() async {
print('running future function');
await Future.delayed(Duration(seconds: 3));
return 'potatoes';
}
Note, to access a provider in initState() you have to set listen to false, as detailed in this answer.

Answer 2

I think you have some things bad in your code, maybe that's not the problem but is good to correct that:
first: It is not recommendable to do that job in your main file, you should have something like a Splash page to handle that.
second: You should use blocs and not write your logic code on the same place at the view(UI)

Answer 3

If you're using android studio, try if running from the terminal fix the issue. The run button attached the debug service, which then force the entire app to be rebuilt