Про Flutter, кратко: Основы

import 'package:flutter/widgets.dart';
import 'dart:math';

main() => runApp(App());

class App extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Directionality(
      child: Container(
        child: ListScreen(),
        color: Color(0xFF386DA7),
      ),
      textDirection: TextDirection.ltr,
    );
  }
}

class ListScreen extends StatelessWidget {
  final double cellSize = 60;
  final itemsAmount = 1000;
  final rng = new Random();

  @override
  Widget build(BuildContext context) {
    return ListView.builder(
      itemCount: itemsAmount,
      itemExtent: cellSize,
      itemBuilder: (BuildContext context, int index) {
        return ListView.builder(
          itemCount: itemsAmount,
          itemExtent: cellSize,
          scrollDirection: Axis.horizontal,
          itemBuilder: (BuildContext context, int index) {
            return Container(
              color: Color(0xFF000000 + rng.nextInt(0xFFFFFF)),
              child: Text(rng.nextInt(0xFFFFFF).toRadixString(16)),
            );
          },
        );
      },
    );
  }
}