Is there a better way of async loading data into CupertinoPicker? - flutter

Question

Is there a better way of async on-demand loading data into CupertinoPicker?
What I basically do is listen to scroll event and detecting if CupertinoPicker is scrolled beyond the start and show a spinner for the duration of the loading of "data". I insert the spinner into the list of widgets built from the data and remove it when new widgets are added to the list.
I can't say what makes me wonder if there is a better way, but I feel there should be a better way of solving this issue.
import 'package:flutter/material.dart';
import 'package:flutter/cupertino.dart';
void main(){
runApp(MyApp());
}
class MyApp extends StatefulWidget {
#override
_MyAppState createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
List<Widget> items = [Divider(color: Colors.red)];
bool refreshInProgress = false;
loadMoreData() {
if(refreshInProgress) return;
setState(() {
refreshInProgress = true;
});
items.insert(0, FutureBuilder(
future: Future.delayed(Duration(seconds: 2)).then((value) {
var newItems = [Text("A"), Text("B"), Text("C")];
setState((){
items = [...newItems, ...items.where((w) => !(w is FutureBuilder) || w == null)];
refreshInProgress = false;
});
return newItems;
}),
builder: (context, snapshot) {
if(snapshot.connectionState == ConnectionState.waiting) return Center(child: CircularProgressIndicator());
return null;
},
));
}
#override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
body: Center(child: Container(
margin: EdgeInsets.all(20),
child: Column(children: [
Expanded(flex: 4, child: NotificationListener<ScrollNotification>(
onNotification: (ScrollNotification notification) {
if ((notification is ScrollEndNotification) && notification.metrics.pixels <= 0) {
loadMoreData();
return true;
}
return false;
},
child: CupertinoPicker.builder(
itemExtent: 32,
itemBuilder: (BuildContext context, int index) {
if(index >= 0 && index < items.length) return Center(child: items[index]);
return null;
},
onSelectedItemChanged: (int value) {
print("onSelectedItemChanged: $value");
},
))
),
Expanded(child: Container(child: Text("$items"))),
Row(children: [
RaisedButton(onPressed: () => setState(() => loadMoreData()), child: Text("Load more data")),
])
],
)),
)),
);
}
}
https://dartpad.dev/b27137f4bff39281980f5957f5e140ad