ExpansionTile

import 'package:flutter/material.dart';

class ExpansionTileSample extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: const Text('ExpansionTile'),
        ),
        body: ListView.builder(
          itemBuilder: (BuildContext context, int index) {
            return Stack(
              children: <Widget>[
                Positioned.fill(
                  child: Column(
                    children: <Widget>[
                      Expanded(
                        child: Container(
                          margin: EdgeInsets.only(left: 17),
                          decoration: BoxDecoration(
                            border: Border(
                              left: BorderSide(color: Colors.blue, width: 2),
                            ),
                          ),
                        ),
                      ),
                      Expanded(
                        child: Container(
                          margin: EdgeInsets.only(left: 17),
                          decoration: BoxDecoration(
                            border: Border(
                              left: BorderSide(color: Colors.blue, width: 2),
                            ),
                          ),
                        ),
                      ),
                    ],
                  ),
                ),
                EntryItem(isFirst: index == 0, isLast: index == 2),
              ],
            );
          },
          itemCount: 3,
        ),
      ),
    );
  }
}

// One entry in the multilevel list displayed by this app.
class Entry {
  Entry(this.title, [this.children = const <Entry>[]]);

  final String title;
  final List<Entry> children;
}

class EntryItem extends StatelessWidget {

  Entry entry;

  final bool isFirst;
  final bool isLast;

  EntryItem({this.isFirst, this.isLast});

  Widget _buildTiles(Entry root) {
    return Row(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: <Widget>[
        Stack(
          children: <Widget>[
            Container(
              margin: const EdgeInsets.only(left: 10, top: 21, right: 10),
              height: 16,
              width: 16,
              decoration: BoxDecoration(
                shape: BoxShape.circle,
                color: Colors.blue,
              ),
            ),
//            Positioned.fill(
//              child: Column(
//                children: <Widget>[
//                  Expanded(
//                    child: Container(
//                      margin: EdgeInsets.only(left: 17),
//                      decoration: BoxDecoration(
//                        border: Border(
//                          left: BorderSide(color: Colors.blue, width: 2),
//                        ),
//                      ),
//                    ),
//                  ),
//                  Expanded(
//                    child: Container(
//                      margin: EdgeInsets.only(left: 17),
//                      decoration: BoxDecoration(
//                        border: Border(
//                          left: BorderSide(color: Colors.blue, width: 2),
//                        ),
//                      ),
//                    ),
//                  ),
//                ],
//              ),
//            ),
          ],
        ),
        Flexible(
          child: ExpansionTile(
            key: PageStorageKey<Entry>(root),
            title: Text('SAMPLE STEP'),
            children: <Widget>[
              ListTile(
                title: Text('Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.'),
              ),
            ],
          ),
        ),
      ],
    );
  }

  @override
  Widget build(BuildContext context) {
    return _buildTiles(entry);
  }
}

void main() {
  runApp(ExpansionTileSample());
}