ArcPainter constructor
ArcPainter({})
默认是画圆
Implementation
ArcPainter(
{this.startAngle = 0.0,
this.sweepAngle = 360.0,
this.color = Colors.blue,
this.middleLabel = '',
this.aboveLabel = '',
this.borderColor = Colors.transparent,
this.strokeWidth = 1});