listviewpagingandloading

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  int page = 1;

  List<String> items = ['item1', 'item2', 'item3', 'item4'];

  bool isLoading = false;

  Future<void> _loadingData() async {
    await Future.delayed(Duration(seconds: 2));

    print('loading more....');
    setState(() {
      items.addAll(['item1']);
      print('items: ' + items.toString());
      isLoading = false;
    });
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Material App',
      home: Scaffold(
          appBar: AppBar(
            title: Text('Material App Bar'),
          ),
          body: Column(
            children: <Widget>[
              //create an indicator when data is being retrieved
              Container(
                height: isLoading ? 50.0:0,
                color: Colors.transparent,
                child: Center(
                  child: CircularProgressIndicator()),
              ),
              //end =============
              //Notification Listener to listen to Scroll
              //Expanded coz the data will expand out listview
              Expanded(
                child: NotificationListener<ScrollNotification>(
                //this part to get notificaion info
                onNotification: (ScrollNotification scrollInfo) {
                  if(!isLoading && scrollInfo.metrics.pixels == scrollInfo.metrics.maxScrollExtent) {
                     _loadingData();
                    setState(() {
                      isLoading = true;
                    });
                  }
                  return null;
                },
                //this part display data in Listview
                child: ListView.builder(
                  itemCount: items.length,
                  itemBuilder: (context, index) {
                    return ListTile(
                      title: Text(items[index]),
                    );
                  },
                ),
                )
              ),

              
            ],
          )),
    );
  }
}