showHandles method Null safety
Builds the handles by inserting them into the context's overlay.
Implementation
void showHandles() {
if (_handles != null) {
return;
}
_handles = <OverlayEntry>[
OverlayEntry(builder: _buildStartHandle),
OverlayEntry(builder: _buildEndHandle),
];
Overlay.of(context, rootOverlay: true, debugRequiredFor: debugRequiredFor)!
.insertAll(_handles!);
}