invalidateExtent method
Invalidates the extent of the item at index. Invalidating extent will
treat the extent as an estimation and will recalculate the extent if the
ExtentPrecalculationPolicy allows for eagerly precalculating extents.
Implementation
void invalidateExtent(int index) {
assert(_delegate != null, "ListController is not attached.");
_delegate!.invalidateExtent(index);
}