createOverlayEntries method
Subclasses should override this getter to return the builders for the overlay.
Implementation
@override
Iterable<OverlayEntry> createOverlayEntries() {
return <OverlayEntry>[
_modalBarrier = OverlayEntry(builder: _buildModalBarrier),
_modalScope =
OverlayEntry(builder: _buildModalScope, maintainState: maintainState),
];
}