import 'dart:math';

import 'package:flutter/material.dart';

void main() => runApp(const ScrolledUnder());

class ScrolledUnder extends StatelessWidget {
  const ScrolledUnder({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        appBar: AppBar(
          backgroundColor: MaterialStateColor.resolveWith((states) {
            if (states.contains(MaterialState.scrolledUnder)) {
              return Colors.red;
            }
            return Colors.blue;
          }),
          title: Text('reverse scrolled under'),
        ),
        body: ListView.builder(
          itemBuilder: (context, index) => Container(
            height: 200,
            color: Color((Random().nextDouble() * 0xFFFFFF).toInt())
                .withOpacity(1.0),
          ),
          reverse: true,
        ),
      ),
    );
  }
}