Pagination View implementation for Big data source

pagination_view.dart

import 'package:flutter/material.dart';

class PaginationView extends StatefulWidget {
  final int maxCountPerPage;
  final int totalCount;
  final Widget Function(BuildContext context, int start, int end) builder;
  final VoidCallback? onNext;
  final VoidCallback? onPrevious;

  const PaginationView({
    Key? key,
    required this.maxCountPerPage,
    required this.totalCount,
    required this.builder,
    this.onNext,
    this.onPrevious,
  }) : super(key: key);

  @override
  State<PaginationView> createState() => _PaginationViewState();
}

class _PaginationViewState extends State<PaginationView> {
  final ValueNotifier<int> _indexNotifier = ValueNotifier(0);

  int get maxPages => (widget.totalCount ~/ widget.maxCountPerPage);

  @override
  Widget build(BuildContext context) {
    return ValueListenableBuilder<int>(
      valueListenable: _indexNotifier,
      builder: (BuildContext context, int pageIndex, Widget? child) {
        final maxPerPage = widget.maxCountPerPage;
        final total = widget.totalCount;
        var startIndex = (pageIndex) * maxPerPage;
        var endIndex = startIndex + maxPerPage;

        startIndex = getProperIndex(startIndex, 0, total - 1);
        endIndex = getProperIndex(endIndex, 0, total);
        return Column(
          children: [
            SizedBox(
              height: 76,
              child: Row(
                mainAxisAlignment: MainAxisAlignment.end,
                children: [
                  _buildButton(
                    icon: Icons.chevron_left,
                    onTap: () {
                      final shouldAllow = _goToPreviousPage();
                      if (shouldAllow) {
                        widget.onPrevious?.call();
                      }
                    },
                  ),
                  _buildText('${startIndex + 1} - ${endIndex + 1}'),
                  _buildButton(
                    icon: Icons.chevron_right,
                    onTap: () {
                      final shouldAllow = _goToNextPage();
                      if (shouldAllow) {
                        widget.onNext?.call();
                      }
                    },
                  ),
                ],
              ),
            ),
            Expanded(
              child: widget.builder(context, startIndex, endIndex),
            ),
          ],
        );
      },
    );
  }

  Widget _buildText(String data) {
    return Padding(
      padding: const EdgeInsets.symmetric(
        horizontal: 20,
      ),
      child: Text(
        data,
        style: const TextStyle(
          fontSize: 20,
          color: Colors.black,
          fontWeight: FontWeight.w700,
        ),
      ),
    );
  }

  bool _goToPreviousPage() {
    final currentPage = _indexNotifier.value;
    if (currentPage <= 0) {
      debugPrint('No previous items');
      return false;
    }
    _indexNotifier.value = currentPage - 1;
    return true;
  }

  bool _goToNextPage() {
    final currentPage = _indexNotifier.value;
    if (currentPage >= maxPages) {
      debugPrint('No next items');
      return false;
    }
    _indexNotifier.value = currentPage + 1;
    return true;
  }

  int getProperIndex(int index, int min, int max) {
    if (index < min) return min;
    if (index >= max) return max;
    return index;
  }


  Widget _buildButton({
    required IconData icon,
    required onTap,
  }) {
    return GestureDetector(
      child: Padding(
        padding: const EdgeInsets.symmetric(
          vertical: 10,
          horizontal: 10,
        ),
        child: Center(
          child: Icon(
            icon,
            color: Colors.black,
            size: 40,
          ),
        ),
      ),
      onTap: onTap,
    );
  }
}