Stack Widget with Google Maps and Container on it in Flutter
This issue is a bid old, but my answer may help others.
I had a similar issue using the Mapbox library instead of Google Maps. My workaround was to define manually the Container Height, and make sure that my foreground container was not taking all the space on the screen.
return new Stack(
children: <Widget>[
new Container(
height: 1000, // This line solved the issue
child: FullMapPage(), // Mapbox
),
new Container(
alignment: Alignment.bottomLeft,
child: FirestoreSlideshow(), // My cards showing in front of the Map's
),
],
);