Get an Integer with Flutter from the Cloud Firestore - flutter

Question

I am new at Flutter and I try to build an App. I want to Display an double on a Textwidget from Cloud Firestore.
My CloudFirestore look like this:
How can I read the double of 200 in a TextWidget and Displays all the time the new value?
I have create a function to add Integer on the specific logged In User Mail what looks like this:
geldNew = _firestore.collection('guthaben').doc(loggedInUser?.email).set({
'geld': geld,
});

Answer 1

You can use a StreamBuilder and the snapshots to stream the value, so when there's a change, the UI gets updated automatically like so:
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: StreamBuilder<DocumentSnapshot>(
stream: FirebaseFirestore.instance
.collection('guthaben')
.doc("loggedInUser?.email")
.snapshots(),
builder: (context, snapshot) {
if (snapshot.hasData) {
return const CircularProgressIndicator();
}
return Text((snapshot.data!.data() as Map)["geld"].toString());
},
),
),
);
}
}
If you want to get the value just once, you can use a FutureBuilder like so:
class HomePage extends StatelessWidget {
const HomePage({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: FutureBuilder<DocumentSnapshot>(
future: FirebaseFirestore.instance
.collection('guthaben')
.doc("loggedInUser?.email")
.get(),
builder: (context, snapshot) {
if (snapshot.hasData) {
return const CircularProgressIndicator();
}
return Text((snapshot.data!.data() as Map)["geld"].toString());
},
),
),
);
}
}