opacity property
Opacity of the series. The value ranges from 0 to 1.
Defaults to 1.
Widget build(BuildContext context) {
  return SfCartesianChart(
    series: <BarSeries<SalesData, num>>[
      BarSeries<SalesData, num>(
        opacity: 0.8
      ),
    ],
  );
}
Implementation
final double opacity;