onDragStart method

void onDragStart(
  1. DragStartDetails details
)

Implementation

void onDragStart(DragStartDetails details) {
  // It's possible for _hold to become null between _handleDragDown and
  // _handleDragStart, for example if some user code calls jumpTo or otherwise
  // triggers a new activity to begin.
  assert(_drag == null);
  _drag = position.drag(details, _disposeDrag);
  assert(_drag != null);
  assert(_hold == null);
}