Why does my async method run twice in Flutter? - flutter

Question

I want to load a static list data when entering indexScreen,but the list sometimes show twice the same content,sometimes not.
This is my list setting:List<ListClass> listItems=List<ListClass>();,ListClass is a simple class with on different attributes and a constructor.
I use home:IndexScreen() in main.dart to show Index page.
return MaterialApp(
home: IndexScreen(),
debugShowCheckedModeBanner: false,
onGenerateRoute: router.generator,
builder: EasyLoading.init(),
);
And before this page build,it will update listItems using:
Future<bool> initUserAndIndex() async{
if (curUserEmail==null) sharedGetData(USER_EMAIL).then((value) => curUserEmail=value.toString());
print(curUserEmail);
await UserTable().getUserInfo(curUserEmail).then((value){print("user ok");});
await CollectionTable().getIndexList().then((value){print("Collection ok");return true;});
return null;
}
buildPage:
#override
Widget build(BuildContext context) {
return FutureBuilder<Object>(
future: initUserAndIndex(),
builder: (BuildContext context, AsyncSnapshot snapshot) {
if (snapshot.connectionState==ConnectionState.waiting)
{
EasyLoading.show(status: 'loading...');
// avoid no return,this cause a whiteborad transition,I don't know how to solve it,too.
return Container();
}
else
{
EasyLoading.dismiss();
return SafeArea(
child: Scaffold(
// the listItems is used in Body()
body: Body(),
),
);
}
},
);
}
}
I run this app,and it prints twice user ok and Collection ok.But when I use ROUTER.NAVIGETE,it only prints once.
User Information is OK,but the list is such a great problem--the page shows twice content
I put my code at an order of relevance of this prblom,I think.Next I put my the two awaited funtion here:
User:
Future<bool> getUserInfo(String userEmail) async{
await userCollection.where({'userEmail':userEmail}).get().then((res) async {
//assign to the static variables
return true;
});
return null;
}
Collection:
Future<bool> getIndexList() async {
listItems.clear();
await listCollection.get().then((value){
var v = value.data;
for (var data in v) {
//get data and package them,add after the listItems list.
listItems.add(ListClass(header, content, userId, favorCount, wordCount));
}
return true;
});
}

Answer 1

You probably want to assign your future in your widget class, but not in the build method as the documentation show, otherwise, everytime your build method is triggered, it will call again your FutureBuilder.
final Future<String> _calculation = Future<String>.delayed(
const Duration(seconds: 2),
() => 'Data Loaded',
);
#override
Widget build(BuildContext context) {
return DefaultTextStyle(
style: Theme.of(context).textTheme.headline2!,
textAlign: TextAlign.center,
child: FutureBuilder<String>(
future: _calculation, // a previously-obtained Future<String> or null
builder: (BuildContext context, AsyncSnapshot<String> snapshot) {
// ...
}
),
),
}