restorationId property Null safety
Restoration ID to save and restore the state of the Scaffold.
If it is non-null, the scaffold will persist and restore whether the drawer and endDrawer was open or closed.
The state of this widget is persisted in a RestorationBucket claimed from the surrounding RestorationScope using the provided restoration ID.
- RestorationManager, which explains how state restoration works in Flutter.
final String? restorationId;