void handleExtentsChanged(double contentExtent, double containerExtent)

Updates the scroll behavior for the new content and container extent.

For convenience, this function combines three common operations:

  1. Updating the scroll behavior extents with ExtentScrollBehavior.updateExtents.
  2. Notifying this object that the scroll behavior was updated with didUpdateScrollBehavior.
  3. Updating this object's gesture detector with updateGestureDetector.

Source 

void handleExtentsChanged(double contentExtent, double containerExtent) {
  didUpdateScrollBehavior(scrollBehavior.updateExtents(
    contentExtent: contentExtent,
    containerExtent: containerExtent,
    scrollOffset: scrollOffset
  ));
  updateGestureDetector();
}