popoverAnchor property
The anchor point on the popover used for positioning relative to the childAnchor.
For example, with popoverAnchor: Alignment.topCenter and childAnchor: Alignment.bottomCenter,
the popover's top edge will align with the child's bottom edge.
Defaults to Alignment.bottomCenter on Android and iOS, and Alignment.topCenter on all other platforms.
Implementation
final AlignmentGeometry popoverAnchor;