AnimatedContainer not working with ListView - flutter

Question

The AnimatedContainer class is not very clear for me. From the code below (that works) - all the children are created in all list views. I want to only populate certain list views - not all. How do I do this?
You can see the code works - no errors, but no matter how much I change this code, I cannot seem to get a list view or card to have uniquely its own children (or expandedContainers).
Its really causing me a lot of distress.
And when I press down the down button, it expands everything, not just the cell I need expanded.
class Home extends StatelessWidget {
#override
Widget build(BuildContext context) {
return new Scaffold(
backgroundColor: Colors.grey,
appBar: new AppBar(
title: new Text("Expandable List"),
backgroundColor: Colors.redAccent,
),
body: new ListView.builder(
itemBuilder: (BuildContext context, int index) {
return new ExpandableListView(title: "Title $index");
},
itemCount: 5,
),
);
}
}
class ExpandableListView extends StatefulWidget {
final String title;
const ExpandableListView({Key key, this.title}) : super(key: key);
#override
_ExpandableListViewState createState() => new _ExpandableListViewState();
}
class _ExpandableListViewState extends State<ExpandableListView> {
bool expandFlag = false;
#override
Widget build(BuildContext context) {
return new Container(
margin: new EdgeInsets.symmetric(vertical: 1.0),
child: new Column(
children: <Widget>[
new Container(
color: Colors.blue,
padding: new EdgeInsets.symmetric(horizontal: 5.0),
child: new Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
new IconButton(
icon: new Container(
height: 50.0,
width: 50.0,
decoration: new BoxDecoration(
color: Colors.orange,
shape: BoxShape.circle,
),
child: new Center(
child: new Icon(
expandFlag ? Icons.keyboard_arrow_up : Icons.keyboard_arrow_down,
color: Colors.white,
size: 30.0,
),
),
),
onPressed: () {
setState(() {
expandFlag = !expandFlag;
});
}),
new Text(
widget.title,
style: new TextStyle(fontWeight: FontWeight.bold, color: Colors.white),
)
],
),
),
new ExpandableContainer(
expanded: expandFlag,
child: new ListView.builder(
itemBuilder: (BuildContext context, int index) {
return new Container(
decoration:
new BoxDecoration(border: new Border.all(width: 1.0, color: Colors.grey), color: Colors.black),
child: new ListTile(
title: new Text(
"Cool $index",
style: new TextStyle(fontWeight: FontWeight.bold, color: Colors.white),
),
leading: new Icon(
Icons.local_pizza,
color: Colors.white,
),
),
);
},
itemCount: 15,
))
],
),
);
}
}
class ExpandableContainer extends StatelessWidget {
final bool expanded;
final double collapsedHeight;
final double expandedHeight;
final Widget child;
ExpandableContainer({
#required this.child,
this.collapsedHeight = 0.0,
this.expandedHeight = 300.0,
this.expanded = true,
});
#override
Widget build(BuildContext context) {
double screenWidth = MediaQuery.of(context).size.width;
return new AnimatedContainer(
duration: new Duration(milliseconds: 500),
curve: Curves.easeInOut,
width: screenWidth,
height: expanded ? expandedHeight : collapsedHeight,
child: new Container(
child: child,
decoration: new BoxDecoration(border: new Border.all(width: 1.0, color: Colors.blue)),
),
);
}
}