Make a dynamic Listview inside a ListView = - flutter

Question

as of the picture down below, I would like to make listview, where it is possible to add more lines(red) under each listview card.
I have implemented the overall listview(green), with the button that should add a list inside the list. Code is at the bottom
The picture is taken from the Strong app
My design right now is as follows:
Expanded(
// ignore: unnecessary_new
child: new ListView.builder(
itemCount: litems.length,
itemBuilder: (BuildContext ctxt, int Index) {
return Card(
child: Padding(
padding: EdgeInsets.all(10),
child: ExpansionTile(
initiallyExpanded: true,
title: Text(
litems[Index],
style: const TextStyle(
fontSize: 20,
fontWeight: FontWeight.bold,
),
),
children: <Widget>[
ElevatedButton(
onPressed: () {
litems.add('hei');
setState(() {});
},
child: const Text('Add Set')),
SizedBox(height: 5),
],
leading: IconButton(
icon: const Icon(
Icons.close,
color: Colors.red,
),
onPressed: () {
litems.removeAt(Index);
setState(() {});
},
),
)));
})),
ElevatedButton(
onPressed: () {
litems.add('hei');
setState(() {});
},
child: const Text('Add Exercises')),

Answer 1

Try my code:
List<List<String>> parent = [];//init Parent
//Parent(Exercises) layout
Column(
children: [
ListView.builder(
itemCount: parent.length,
shrinkWrap: true,
itemBuilder: (context, index) {
return _buildList(parent[index]);
}),
TextButton(
onPressed: () {
parent.add([]);
setState(() {});
},
child: Text("Add Parent"))
],
)
//build children
_buildList(List<String> list) {
return Column(
children: [
ListView.builder(
itemCount: list.length,
shrinkWrap: true,
padding: EdgeInsets.all(0),
physics: const NeverScrollableScrollPhysics(),
itemExtent: 50,
itemBuilder: (context, index) {
return Container(
color: Colors.red.withOpacity((index * 5) / 100),
margin: EdgeInsets.symmetric(vertical: 0),
child: Text('Item'),
);
},
),
TextButton(
onPressed: () {
list.add("value");
setState(() {});
},
child: Text("Add Item"))
],
);
}