Flutter - Positioned Widget in Stack causing Exception - dart

Question

I'm getting the below exception when I try to encapsulate the PandemicCard with a Positioned widget. If I render the card lone/no Positioned widget, it works just fine.
I/flutter ( 7331): ══╡ EXCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════
I/flutter ( 7331): The following assertion was thrown during performLayout():
I/flutter ( 7331): RenderStack object was given an infinite size during layout.
I/flutter ( 7331): This probably means that it is a render object that tries to be as big as possible, but it was put
I/flutter ( 7331): inside another render object that allows its children to pick their own size.
I/flutter ( 7331): The nearest ancestor providing an unbounded height constraint is:
I/flutter ( 7331): RenderFlex#2b18c relayoutBoundary=up2 NEEDS-LAYOUT NEEDS-PAINT OVERFLOWING
I/flutter ( 7331): creator: Column ← Center ← MediaQuery ← LayoutId-[<_ScaffoldSlot.body>] ← CustomMultiChildLayout ←
For this code. Anyone able to help me figure out what I'm doing wrong?
class PandemicCard extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Container(
height: 120.0,
width: 76.0,
decoration: BoxDecoration(
color: Colors.blue,
boxShadow: [
BoxShadow(
blurRadius: 5.0,
color: Colors.grey)
]),
child: Text('Hi'),
);
}
}
class PandemicCardStackState extends State<PandemicCardStack> {
// final _cards = <PandemicCard>[ PandemicCard(), PandemicCard()];
final _cards = <PandemicCard>[ PandemicCard()];
#override
Widget build( BuildContext context) {
return Stack(
// This Bombs!
children: <Widget>[ Positioned( left: 0.0, top: 0.0, child: _cards[0])]
// This works!
// children: <Widget>[ _cards[0]]
);
}
}
class PandemicCardStack extends StatefulWidget {
#override
PandemicCardStackState createState() => PandemicCardStackState();
}

Answer 1

Add an empty Container as a child of the stack :
#override
Widget build( BuildContext context) {
return Stack(
children: <Widget>[
Container(),
Positioned( left: 0.0, top: 0.0, child: _cards[0]),
]
);
}

Answer 2

Other workarounds:
(a) Wrap the Stack on a Container with a known height:
Container(
height: 50,
child: Stack(
children: [
Positioned(top: 10, left: 10, child: Text('My child'))
]),
),
(b) As suggested add empty Container() and Clip.none:
Stack(
clipBehavior: Clip.none,
children: [
Container(),
Positioned(top: 10, left: 10, child: Text('My child'))
]),

Answer 3

Since this is still an issue. I also came across another option.
You can wrap your stack in an IntrinsicHeight widget as well.
IntrinsicHeight(
child:
Stack(
children: [Positioned(top: 10, left: 10, child:Text('My child')
)]
),
),