paint method
Paint method for the sub class to override and render their loading style
Implementation
@override
void paint(Canvas canvas, Paint paint, Size size) {
var circleSpacing = 4;
var width = size.width;
var height = size.height;
paint.color = paint.color.withAlpha(mAlpha);
canvas.drawCircle(Offset(width / 2, height / 2),
(width / 2 - circleSpacing) * mScale, paint);
}