circle method
Implementation
void circle(Canvas canvas, Rect rect, double minRadius, int wave,
double value, int length) {
Color _color;
double r;
Offset offset=rect.center;
if (wave != 0) {
double opacity = (1 - ((wave - 1) / length) - value).clamp(0.0, 1);
_color = color.withOpacity(opacity);
r = (minRadius * (1 + ((wave * (value+2)))) * (value+0.2));
final Rect rect = Rect.fromCircle(center: offset,radius: r);
// final Paint paint = Paint()..color = _color;
final paint = Paint()
..color = _color
..strokeWidth = 1
..style = PaintingStyle.stroke
..strokeCap = StrokeCap.round;
canvas.drawRect(rect, paint);
}
}