lazy_grid_view_builder.dart

import 'package:flutter/material.dart';

void main() {
  runApp(LazyGridViewApp());
}

class LazyGridViewApp extends StatelessWidget {
  final _list = List.generate(42, (index) => index);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Lazy Grid View'),
        ),
        body: CustomScrollView(
          slivers: [
            SliverGrid(
              delegate: SliverChildBuilderDelegate(
                (context, index) {
                  return Container(
                    color: Colors.blue.withOpacity(index.isEven ? .1 : .4),
                    child: Center(
                      child: Text(index.toString()),
                    ),
                  );
                },
                childCount: _list.length,
              ),
              gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
                crossAxisCount: 3,
              ),
            ),
            SliverToBoxAdapter(
              child: Center(
                child: Padding(
                  padding: const EdgeInsets.all(15),
                  child: CircularProgressIndicator(),
                ),
              ),
            ),
          ],
        ),
      ),
    );
  }
}