longPress method

Future<void> longPress (Finder finder, { int pointer })

Dispatch a pointer down / pointer up sequence (with a delay of kLongPressTimeout + kPressTimeout between the two events) at the center of the given widget, assuming it is exposed.

If the center of the widget is not exposed, this might send events to another object.

Implementation 

Future<void> longPress(Finder finder, { int pointer }) {
  return longPressAt(getCenter(finder), pointer: pointer);
}