estimateMaxScrollOffset method
Returns an estimate of the max scroll extent for all the children.
Subclasses should override this function if they have additional information about their max scroll extent.
The default implementation returns null, which causes the caller to extrapolate the max scroll offset from the given parameters.
Implementation
double estimateMaxScrollOffset(
int firstIndex,
int lastIndex,
double leadingScrollOffset,
double trailingScrollOffset,
) => null;