Flutter Infinite List Controller

infinite_list_controller.dart

import 'package:flutter/foundation.dart';

class InfiniteListPage<T> {
  final List<T> items;
  final int totalCount;

  InfiniteListPage(this.items, this.totalCount);
}

class InfiniteListController<T> extends ChangeNotifier {
  final Future<InfiniteListPage<T>> Function(int offset) loadPage;

  InfiniteListController({
    required this.loadPage,
  });

  var _totalCount = -1;
  var _loading = false;
  var _items = <T>[];
  Exception? _exception;

  Exception? get exception => _exception;
  bool get loading => _loading;
  List<T> get items => _items;

  void reload() {
    if (_loading) return;

    _exception = null;
    _totalCount = -1;
    _items = [];
    _loadPage();
  }

  void loadMore() {
    final hasMore = _items.length < _totalCount;
    if (!hasMore || _loading) return;

    _loadPage();
  }

  void _loadPage() async {
    _loading = true;
    notifyListeners();

    try {
      final page = await loadPage(_items.length);
      _items = [..._items, ...page.items];
      _totalCount = page.totalCount;
    } on Exception catch (exception) {
      _exception = exception;
    } finally {
      _loading = false;
    }
    notifyListeners();
  }
}