* @param lly
     * @param urx
     * @param ury
     * @param on
     */
    public void drawRadioField(float llx, float lly, float urx, float ury, final boolean on) {
        if (llx > urx) { float x = llx; llx = urx; urx = x; }
        if (lly > ury) { float y = lly; lly = ury; ury = y; }
        saveState();
        // silver circle
        setLineWidth(1);
        setLineCap(1);
        setColorStroke(new BaseColor(0xC0, 0xC0, 0xC0));
        arc(llx + 1f, lly + 1f, urx - 1f, ury - 1f, 0f, 360f);
        stroke();
        // gray circle-segment
        setLineWidth(1);
        setLineCap(1);
        setColorStroke(new BaseColor(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 BaseColor(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 BaseColor(0x00, 0x00, 0x00));
            arc(llx + 4f, lly + 4f, urx - 4f, ury - 4f, 0, 360);
            fill();
        }
        restoreState();
    }