onHorizontalDragUpdate property Null safety

GestureDragUpdateCallback? onHorizontalDragUpdate

Called when the user scrolls to the left or to the right.

Implementation

GestureDragUpdateCallback? get onHorizontalDragUpdate => _onHorizontalDragUpdate;
void onHorizontalDragUpdate=(GestureDragUpdateCallback? value)

Implementation

set onHorizontalDragUpdate(GestureDragUpdateCallback? value) {
  if (_onHorizontalDragUpdate == value)
    return;
  final bool hadHandler = _onHorizontalDragUpdate != null;
  _onHorizontalDragUpdate = value;
  if ((value != null) != hadHandler)
    markNeedsSemanticsUpdate();
}