onDragStart property
Stream<DraggableEvent>
onDragStart
Fired when the user starts dragging.
Note: The onDragStart is fired not on touchStart or mouseDown but as soon as there is a drag movement. When a drag is started an onDrag event will also be fired.
Implementation
Stream<DraggableEvent> get onDragStart {
if (_onDragStart == null) {
_onDragStart = StreamController<DraggableEvent>.broadcast(
sync: true, onCancel: () => _onDragStart = null);
}
return _onDragStart!.stream;
}