drag method
Attempts to drag the given widget by the given offset, by starting a drag in the middle of the widget.
If the middle of the widget is not exposed, this might send events to another object.
If you want the drag to end with a speed so that the gesture recognition system identifies the gesture as a fling, consider using fling instead.
Implementation
Future<void> drag(Finder finder, Offset offset, { int pointer }) {
return dragFrom(getCenter(finder), offset, pointer: pointer);
}