flutter/examples/api/lib/widgets/scrollbar/raw_scrollbar.0.dart

// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// Template: dev/snippets/config/templates/stateful_widget_scaffold_center.tmpl
//
// Comment lines marked with "▼▼▼" and "▲▲▲" are used for authoring
// of samples, and may be ignored if you are just exploring the sample.

// Flutter code sample for RawScrollbar
//
//***************************************************************************
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// This sample shows an app with two scrollables in the same route. Since by
// default, there is one [PrimaryScrollController] per route, and they both have a
// scroll direction of [Axis.vertical], they would both try to attach to that
// controller. The [Scrollbar] cannot support multiple positions attached to
// the same controller, so one [ListView], and its [Scrollbar] have been
// provided a unique [ScrollController].
//
// Alternatively, a new PrimaryScrollController could be created above one of
// the [ListView]s.

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//***************************************************************************

import 'package:flutter/material.dart';

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

/// This is the main application widget.
class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  static const String _title = 'Flutter Code Sample';

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: _title,
      home: Scaffold(
        appBar: AppBar(title: const Text(_title)),
        body: const Center(
          child: MyStatefulWidget(),
        ),
      ),
    );
  }
}

/// This is the stateful widget that the main application instantiates.
class MyStatefulWidget extends StatefulWidget {
  const MyStatefulWidget({Key? key}) : super(key: key);

  @override
  State<MyStatefulWidget> createState() => _MyStatefulWidgetState();
}

/// This is the private State class that goes with MyStatefulWidget.
class _MyStatefulWidgetState extends State<MyStatefulWidget> {
//********************************************************************
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  final ScrollController _firstController = ScrollController();

  @override
  Widget build(BuildContext context) {
    return LayoutBuilder(
        builder: (BuildContext context, BoxConstraints constraints) {
      return Row(
        children: <Widget>[
          SizedBox(
              width: constraints.maxWidth / 2,
              // Only one scroll position can be attached to the
              // PrimaryScrollController if using Scrollbars. Providing a
              // unique scroll controller to this scroll view prevents it
              // from attaching to the PrimaryScrollController.
              child: Scrollbar(
                isAlwaysShown: true,
                controller: _firstController,
                child: ListView.builder(
                    controller: _firstController,
                    itemCount: 100,
                    itemBuilder: (BuildContext context, int index) {
                      return Padding(
                        padding: const EdgeInsets.all(8.0),
                        child: Text('Scrollable 1 : Index $index'),
                      );
                    }),
              )),
          SizedBox(
              width: constraints.maxWidth / 2,
              // This vertical scroll view has not been provided a
              // ScrollController, so it is using the
              // PrimaryScrollController.
              child: Scrollbar(
                isAlwaysShown: true,
                child: ListView.builder(
                    itemCount: 100,
                    itemBuilder: (BuildContext context, int index) {
                      return Container(
                          height: 50,
                          color: index.isEven
                              ? Colors.amberAccent
                              : Colors.blueAccent,
                          child: Padding(
                            padding: const EdgeInsets.all(8.0),
                            child: Text('Scrollable 2 : Index $index'),
                          ));
                    }),
              )),
        ],
      );
    });
  }

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//********************************************************************

}