onVerticalDragUpdate property

GestureDragUpdateCallback onVerticalDragUpdate

Called when the user scrolls up or down.

Implementation 

GestureDragUpdateCallback get onVerticalDragUpdate => _onVerticalDragUpdate;
void onVerticalDragUpdate= (GestureDragUpdateCallback value)

Implementation 

set onVerticalDragUpdate(GestureDragUpdateCallback value) {
  if (_onVerticalDragUpdate == value)
    return;
  final bool hadHandler = _onVerticalDragUpdate != null;
  _onVerticalDragUpdate = value;
  if ((value != null) != hadHandler)
    markNeedsSemanticsUpdate();
}