insert method
Inserts entry into the overlay, optionally positioned relative to below or above.
Implementation
void insert(OverlayEntry entry, {OverlayEntry? below, OverlayEntry? above}) {
entry._overlay = this;
if (below != null) {
final index = _entries.indexOf(below);
_entries.insert(index, entry);
} else if (above != null) {
final index = _entries.indexOf(above);
_entries.insert(index + 1, entry);
} else {
_entries.add(entry);
}
setState(() {});
}