lengthUnit property

Calculates the pointer tail length either in logical pixel or radius factor.

Using GaugeSizeUnit, pointer tail length is calculated.

Defaults to GaugeSizeUnit.factor.

Also refer GaugeSizeUnit

Widget build(BuildContext context) {
   return Container(
       child: SfRadialGauge(
         axes:<RadialAxis>[RadialAxis
         ( pointers: <GaugePointer>[
            NeedlePointer( tailStyle:
                TailStyle(length: 30,
                lengthUnit: GaugeSizeUnit.logicalPixel, width: 10)
          )])]
       ));
}