saveScrollOffset method
Called whenever scrolling ends, to store the current scroll offset in a storage mechanism with a lifetime that matches the app's lifetime.
The stored value will be used by restoreScrollOffset when the ScrollPosition is recreated, in the case of the Scrollable being disposed then recreated in the same session. This might happen, for instance, if a ListView is on one of the pages inside a TabBarView, and that page is displayed, then hidden, then displayed again.
The default implementation writes the pixels using the nearest PageStorage found from the context's ScrollContext.storageContext property.
Implementation
// TODO(goderbauer): Deprecate this when state restoration supports all features of PageStorage.
@protected
void saveScrollOffset() {
PageStorage.maybeOf(context.storageContext)?.writeState(context.storageContext, pixels);
}