import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Scrollbar',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.green),
        useMaterial3: false,
      ),
      home: const MyHomePage(title: 'Flutter Scrollbar'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  final _scrollController = ScrollController();

  String _buildMessages() {
    const messages = "Hello there";
    return List<String>.filled(30, messages).join('\n');
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.start,
          children: <Widget>[
            Scrollbar(
              thumbVisibility: true,
              thickness: 6,
              controller: _scrollController,
              child: TextField(
                scrollController: _scrollController,
                maxLines: 9,
                readOnly: true,
                controller: TextEditingController(text: _buildMessages()),
              ),
            ),
          ],
        ),
      ),
    );
  }
}