drag method

  1. @override
Drag drag(
  1. DragStartDetails details,
  2. VoidCallback dragCancelCallback

Start a drag activity corresponding to the given DragStartDetails.

The onDragCanceled argument will be invoked if the drag is ended prematurely (e.g. from another activity taking over). See ScrollDragController.onDragCanceled for details.


Drag drag(DragStartDetails details, VoidCallback dragCancelCallback) {
  final ScrollDragController drag = ScrollDragController(
    delegate: this,
    details: details,
    onDragCanceled: dragCancelCallback,
    carriedVelocity: physics.carriedMomentum(_heldPreviousVelocity),
    motionStartDistanceThreshold: physics.dragStartDistanceMotionThreshold,
  beginActivity(DragScrollActivity(this, drag));
  assert(_currentDrag == null);
  _currentDrag = drag;
  return drag;