1. override
BoxPainter createBoxPainter([VoidCallback onChanged ])

Returns a BoxPainter that will paint this decoration.

The onChanged argument configures BoxPainter.onChanged. It can be omitted if there is no chance that the painter will change (for example, if it is a BoxDecoration with definitely no BackgroundImage).

Source 

@override
BoxPainter createBoxPainter([VoidCallback onChanged]) {
  assert(debugAssertIsValid());
  return new _FlutterLogoPainter(this);
}