build method
Build the widget.
Implementation
@override
Widget build(final BuildContext context) => GestureDetector(
onDoubleTap: onDoubleTap,
onPanDown: (final details) => onMove(details.localPosition),
onPanEnd: (final details) => onMove(details.localPosition),
onPanUpdate: (final details) => onMove(details.localPosition),
);