Always show scrollbar – Flutter

Updated Answer April 2023

As of v2.9.0-1.0.pre, isAlwaysShown is deprecated and you should use thumbVisibility instead. Check jayjw’s more complete answer: https://stackoverflow.com/a/71357052/9777674

Original Answer June 2020

As of Flutter version 1.17, on Scrollbar you can set isAlwaysShown to true, but you must set the same controller for your Scrollbar and your SingleChildScrollView (and that applies to any other scrollable Widget as well).

Have in mind that, for the Scrollbar to be visible, there must be enough items to scroll. If there are not, the Scrollbar won’t be shown.

Full working example:

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: MyWidget(),
      ),
    );
  }
}

class MyWidget extends StatefulWidget {  
  @override
  _MyWidgetState createState() => _MyWidgetState();
}

class _MyWidgetState extends State<MyWidget> {
  final _scrollController = ScrollController();
  
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Padding(
        padding: const EdgeInsets.all(15.0),
        child: Center(
          child: Column(
            children: <Widget>[
              // ...
              Expanded(
                child: Scrollbar(
                  controller: _scrollController, // <---- Here, the controller
                  isAlwaysShown: true, // <---- Required
                  child: SingleChildScrollView(
                    controller: _scrollController, // <---- Same as the Scrollbar controller
                    child: Text(
                      "Long Text Here ...",
                      textDirection: TextDirection.rtl,
                      style: TextStyle(fontSize: 17.2),
                    ),
                  ),
                ),
              ),
              // ...
            ],
          ),
        ),
      ),
    );
  }
}