draw method

@override void draw(Canvas canvas, ChartsState state)

Implementation

@override
void draw(Canvas canvas, ChartsState state) {
  _ChartCircularCoordinateState layout = state.layout as _ChartCircularCoordinateState;
  Offset center = layout.center;
  double radius = layout.radius;
  int index = 0;
  num? lastXvs;
  double startAngle = this.startAngle;
  double fullSweepAngle = math.pi;
  //
  if (layout.arcPosition == ArcPosition.none) {
    fullSweepAngle = math.pi * 2;
  } else if (layout.arcPosition == ArcPosition.up) {
    fullSweepAngle = math.pi;
  } else if (layout.arcPosition == ArcPosition.down) {
    startAngle = 0;
  }

  for (T item in data) {
    num po = position.call(item);
    if (lastXvs != null) {
      assert(lastXvs > po, '数据必须降序，否则会被挡住');
    }
    double sweepAngle = fullSweepAngle * po * layout.controlValue;
    Path path = Path()
      ..addArc(
        Rect.fromCenter(center: center, width: radius * 2, height: radius * 2),
        startAngle,
        sweepAngle,
      );
    canvas.drawPath(path, _paint..color = colors[index]);
    if (_endPaint != null && sweepAngle > 0) {
      double endAngle = startAngle + sweepAngle;
      var startX = math.cos(endAngle) * radius + center.dx;
      var startY = math.sin(endAngle) * radius + center.dy;
      canvas.drawCircle(Offset(startX, startY), strokeWidth / 2 - 2, _endPaint!);
    }
    index++;
    lastXvs = po;
  }
}