Error while returning the number of count of collections in firebase flutter? - firebase

Question

i'm developing an admin app in that i'm tired to return the number of users from firebase, i got few help from stackoverflow and was able to print in the terminal but its returning null on the app can someone please help me.this my code
class _AdminState extends State<Admin> {
Future<String> getUsersCount() async{
var length = -1;
await Firestore.instance.collection('users').getDocuments().then((myDocuments){
print("${myDocuments.documents.length}");
length = myDocuments.documents.length;
});
return Future.value(length.toString());
}
Page _selectedPage = Page.dashboard;
MaterialColor active = Colors.indigo;
MaterialColor notActive = Colors.grey;
final databaseReference = Firestore.instance;
bool isDelete= true;
var values;
TextEditingController categoryController = TextEditingController();
TextEditingController brandController = TextEditingController();
GlobalKey<FormState> _categoryFormKey = GlobalKey();
//GlobalKey<FormState> _brandFormKey = GlobalKey();
// BrandService _brandService = BrandService();
CategoryService _categoryService = CategoryService();
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Row(
children: <Widget>[
Expanded(
child: FlatButton.icon(
onPressed: () {
setState(() => _selectedPage = Page.dashboard);
},
icon: Icon(
Icons.dashboard,
color: _selectedPage == Page.dashboard
? active
: notActive,
),
label: Text('Dashboard'))),
Expanded(
child: FlatButton.icon(
onPressed: () {
setState(() => _selectedPage = Page.manage);
},
icon: Icon(
Icons.sort,
color:
_selectedPage == Page.manage ? active : notActive,
),
label: Text('Manage'))),
],
),
elevation: 0.0,
backgroundColor: Colors.white,
),
body: _loadScreen());
}
Widget _loadScreen() {
switch (_selectedPage) {
case Page.dashboard:
return FutureBuilder(
future: getUsersCount(),
builder: (BuildContext context, AsyncSnapshot<String> text) {
print(text);
if(text== "-1"){
return CircularProgressIndicator();
} else {
return Column(
children: <Widget>[
ListTile(
subtitle: Text('Admin View', textAlign: TextAlign.center,
style: TextStyle(fontSize: 29.0,
color: Colors.indigo,
fontWeight: FontWeight.bold),),
),
Expanded(child: GridView(
gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
crossAxisCount: 2,),
children: <Widget>[
Padding(
padding: const EdgeInsets.all(18.0), child: Card(
child: ListTile(title: FlatButton.icon(
onPressed: null,
icon: Icon(
Icons.directions_boat, color: Colors.black,),
label: Text("Boats", style: TextStyle(
fontSize: 9, color: Colors.indigo),)),
subtitle: Text('3', textAlign: TextAlign.center,
style: TextStyle(
color: active, fontSize: 50.0),)),
),
),
Padding(padding: const EdgeInsets.all(18.0),
child: Card(child: ListTile(
title: FlatButton.icon(
onPressed: null,
icon: Icon(
Icons.people, color: Colors.black,),
label: Text("Users", style: TextStyle(
fontSize: 9, color: Colors.indigo),)),
subtitle: Text(text.data != null ? text.data : '',
textAlign: TextAlign.center,
style: TextStyle(color: active, fontSize: 50.0),
)),
),
),
Padding(
padding: const EdgeInsets.all(22.0),
child: Card(
child: ListTile(
title: FlatButton.icon(
onPressed: null,
icon: Icon(
Icons.bookmark, color: Colors.black,),
label: Text("Bookings", style: TextStyle(
fontSize: 8, color: Colors.indigo),)),
subtitle: Text(
'120',
textAlign: TextAlign.center,
style: TextStyle(
color: active, fontSize: 50.0),
)),
),
),
],
),
),
],
);
} })
i was returning a null string value but when include this set of lines Text(text.data??'default value') i was able to clear that error but still not able to clear my issue someone please help me

Answer 1

You need to add await before getting data from Firestore, since it is and async and you are not waiting for the result and returning the value which is initialized to 0
Future<String> getUsersCount() async {
var length = 0;
await Firestore.instance.collection('users').getDocuments().then((myDocuments){
print("${myDocuments.documents.length}");
length = myDocuments.documents.length;
});
return Future.value(length.toString());
}
As you can see the value of users count(36) is getting printed but it is not return because the return gets called before the async execution is getting finish..

Answer 2

Initialize your length to -1 in getUsersCount method and then in build method before returning the cloumn widget check the text (snapshot value) :
if (text == "-1"){
return Center(
child: CircularProgressIndicator(backgroundColor: Colors.red,)
);
} else{
return Column(....)
}