code: public void drawRadioField(float llx, float lly, float urx, float ury, boolean on) {
          if (llx > urx) { float x = llx; llx = urx; urx = x; }
          if (lly > ury) { float y = lly; lly = ury; ury = y; }
          // silver circle
          setLineWidth(1);
          setLineCap(1);
          setColorStroke(new Color(0xC0, 0xC0, 0xC0));
          arc(llx + 1f, lly + 1f, urx - 1f, ury - 1f, 0f, 360f);
          stroke();
          // gray circle-segment
          setLineWidth(1);
          setLineCap(1);
          setColorStroke(new Color(0xA0, 0xA0, 0xA0));
          arc(llx + 0.5f, lly + 0.5f, urx - 0.5f, ury - 0.5f, 45, 180);
          stroke();
          // black circle-segment
          setLineWidth(1);
          setLineCap(1);
          setColorStroke(new Color(0x00, 0x00, 0x00));
          arc(llx + 1.5f, lly + 1.5f, urx - 1.5f, ury - 1.5f, 45, 180);
          stroke();
          if (on) {
              // gray circle
              setLineWidth(1);
              setLineCap(1);
              setColorFill(new Color(0x00, 0x00, 0x00));
              arc(llx + 4f, lly + 4f, urx - 4f, ury - 4f, 0, 360);
              fill();
          }
      }
docs: Draws a TextField.
  @param llx
  @param lly
  @param urx
  @param ury
  @param on