infinite scroll

infinite_scroll.dart

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({
    super.key,
  });

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  final ScrollController _c = ScrollController();
  final List<int> _itemList = [];
  final _displayCount = 4;
  final _itemCount = 30;
  double? offset = 0;
  @override
  void initState() {
    super.initState();
    for (var i = 0; i < _itemCount; i++) {
      _itemList.add(i);
    }
    var displayValue = 0;
    var displayTextValue = 0;
    _c.addListener(() {
      setState(() {
        var value = (MediaQuery.of(context).size.width / _displayCount) / 2;
        if (_c.position.pixels == _c.position.maxScrollExtent) {
          offset = null;
          displayValue += _displayCount;
          displayTextValue += _itemList.length;
          _infinityAnimation(
            displayValue,
            displayTextValue,
            0,
          );
        } else if (_c.offset < -value && _itemList.first != 0) {
          offset = null;
          displayValue -= _displayCount;
          displayTextValue -= _itemList.length;
          _infinityAnimation(
            displayValue,
            displayTextValue,
            _c.position.maxScrollExtent / 1.0001,
          );
        }
      });
    });
  }

  Future<void> _infinityAnimation(int d, int d2, double d3) async {
    for (var i = 0; i < _itemCount; i++) {
      _itemList[i] = i + d2 - d;
    }
    offset = d3;
    _c.jumpTo(d3);
  }

  Future<double?> setValue() async {
    return offset;
  }

  @override
  Widget build(BuildContext context) {
    var value = MediaQuery.of(context).size.width / _displayCount;
    return Scaffold(
      appBar: AppBar(
        title: const Text('ListView.builder'),
        centerTitle: true,
      ),
      body: Center(
        child: SizedBox(
          height: 200,
          child: ListView.builder(
            controller: _c,
            scrollDirection: Axis.horizontal,
            itemCount: _itemList.length,
            itemBuilder: (BuildContext context, int index) {
              return Container(
                alignment: Alignment.center,
                height: value,
                width: value,
                color: index.isOdd ? Colors.white : Colors.red,
                child: FutureBuilder(
                  future: setValue(),
                  builder: (BuildContext context, AsyncSnapshot snapshot) {
                    if (snapshot.hasData) {
                      return TextButton.icon(
                        onPressed: () {},
                        icon: const Icon(Icons.add),
                        label: Text('${_itemList[index]}'),
                      );
                    } else {
                      return Container();
                    }
                  },
                ),
              );
            },
          ),
        ),
      ),
    );
  }
}