I can't add my pie chart to cvitem

Question

I have a pie chart as below:

\documentclass[14pt,a4paper,san]{moderncv}   % possible options include font size ('10pt', '11pt' and '12pt'), paper size ('a4paper', 'letterpaper', 'a5paper', 'legalpaper', 'executivepaper' and 'landscape') and font family ('sans' and 'roman')

\moderncvstyle{classic}                        % 选项参数是 ‘casual’, ‘classic’, ‘oldstyle’ 和 ’banking’
\moderncvcolor{blue}                          % 选项参数是 ‘blue’ (默认)、‘orange’、‘green’、‘red’、‘purple’ 和 ‘grey’

\name{a}{a}
\title{s}
\address{}{s}
\email{}
\phone[mobile]{1212}
\begin{document}

\cvitem{}{
\def\angle{0}
\def\radius{3}
\def\cyclelist{{"orange","blue","red","green"}}
\newcount\cyclecount \cyclecount=-1
\newcount\ind \ind=-1
\begin{tikzpicture}[nodes = {font=\sffamily}]
  \foreach \percent/\name in {
      8/C++,8/Linux,7/Arduino,6/Python,6/Erlang,5/H5
    } {
      \ifx\percent\empty\else               % If \percent is empty, do nothing
        \global\advance\cyclecount by 1     % Advance cyclecount
        \global\advance\ind by 1            % Advance list index
        \ifnum3<\cyclecount                 % If cyclecount is larger than list
          \global\cyclecount=0              %   reset cyclecount and
          \global\ind=0                     %   reset list index
        \fi
        \pgfmathparse{\cyclelist[\the\ind]} % Get color from cycle list
        \edef\color{\pgfmathresult}         %   and store as \color
        % Draw angle and set labels
        \draw[fill={\color!50},draw={\color}] (0,0) -- (\angle:\radius)
          arc (\angle:\angle+\percent*1.8*2.5:\radius) -- cycle;

        \node at (\angle+0.5*\percent*1.8*2.5:0.7*\radius) {\name};
        %\node[pin=\angle+0.5*\percent*3.6:\name]
        %  at (\angle+0.5*\percent*3.6:\radius) {};
        \pgfmathparse{\angle+\percent*1.8*2.5}  % Advance angle
        \xdef\angle{\pgfmathresult}         %   and store in \angle
      \fi
    };
\end{tikzpicture}}

\clearpage
\end{document}

But when I copy them into \cvitem{}{$here}. I got lots of error.

file: 'file:///c%3A/Users/erow/Documents/tex/cv1.tex' severity: '错误' message: 'Paragraph ended before \cvitem was complete \par l.74
' at: '74,1' source: 'LaTeX' code: 'undefined'

file: 'file:///c%3A/Users/erow/Documents/tex/cv1.tex' severity: '错误' message: 'Undefined control sequence \pgffor@body ...else \global \advance \cyclecount by 1 \global \advance \ind... l.98 } ; c:/Users/erow/Documents/tex/cv1.tex:98: You can't use the letter b' after \advance. \pgffor@body ...lse \global \advance \cyclecount b y 1 \global \advance \ind ... l.98 } ; c:/Users/erow/Documents/tex/cv1.tex:98: Undefined control sequence. \pgffor@body ...ecount by 1 \global \advance \ind by 1 \ifnum 3<\cyclecount ... l.98 } ; c:/Users/erow/Documents/tex/cv1.tex:98: You can't usethe letter b' after \advance. \pgffor@body ...count by 1 \global \advance \ind b y 1 \ifnum 3<\cyclecount ... l.98 } ; c:/Users/erow/Documents/tex/cv1.tex:98: Undefined control sequence. \pgffor@body ...ce \ind by 1 \ifnum 3<\cyclecount \global \cyclecount =0 \gl... l.98 } ; c:/Users/erow/Documents/tex/cv1.tex:98: Missing number, treated as zero. \global l.98 } ; c:/Users/erow/Documents/tex/cv1.tex:98: Undefined control sequence. \cyclelist [\the \ind ] l.98 } ; c:/Users/erow/Documents/tex/cv1.tex:98: Undefined control sequence. \cyclelist [\the \ind ] l.98 } ; c:/Users/erow/Documents/tex/cv1.tex:98: You can't use `the character ]' after \the. \cyclelist [\the \ind ]
' at: '98,1' source: 'LaTeX' code: 'undefined'

Answer 1

OK. I guess that an MNWE looks like this:

\documentclass[14pt,a4paper,san]{moderncv}
\moderncvstyle{classic}
\moderncvcolor{blue}
\name{a}{a}
\title{s}
\address{}{s}
\email{}
\phone[mobile]{1212}
\begin{document}

\cvitem{}{%
  \def\angle{0}
  \def\radius{3}
  \def\cyclelist{{"orange","blue","red","green"}}
  \newcount\cyclecount \cyclecount=-1
  \newcount\ind \ind=-1
  \begin{tikzpicture}[nodes = {font=\sffamily}]
    \foreach \percent/\name in {
      8/C++,8/Linux,7/Arduino,6/Python,6/Erlang,5/H5
    } {
      \ifx\percent\empty\else               % If \percent is empty, do nothing
      \global\advance\cyclecount by 1     % Advance cyclecount
      \global\advance\ind by 1            % Advance list index
      \ifnum3<\cyclecount                 % If cyclecount is larger than list
      \global\cyclecount=0              %   reset cyclecount and
      \global\ind=0                     %   reset list index
      \fi
      \pgfmathparse{\cyclelist[\the\ind]} % Get color from cycle list
      \edef\color{\pgfmathresult}         %   and store as \color
      % Draw angle and set labels
      \draw[fill={\color!50},draw={\color}] (0,0) -- (\angle:\radius) arc (\angle:\angle+\percent*1.8*2.5:\radius) -- cycle;

      \node at (\angle+0.5*\percent*1.8*2.5:0.7*\radius) {\name};
      \pgfmathparse{\angle+\percent*1.8*2.5}  % Advance angle
      \xdef\angle{\pgfmathresult}         %   and store in \angle
      \fi
    };
  \end{tikzpicture}%
}

\clearpage
\end{document}

which returns

Runaway argument?
{\def \angle {0} \def \radius {3} \def \cyclelist {{"orange","blue","\ETC.
! Paragraph ended before \\cvitem was complete.
<to be read again> 
                   \par 
l.45 

?

The problem here is that you have a paragraph break in the argument to \cvitem i.e. a blank line. So, a minimal fix would be

\documentclass[14pt,a4paper,san]{moderncv}
\moderncvstyle{classic}
\moderncvcolor{blue}
\name{a}{a}
\title{s}
\address{}{s}
\email{}
\phone[mobile]{1212}
\begin{document}
\cvitem{pie chart}{%
  \def\angle{0}
  \def\radius{3}
  \def\cyclelist{{"orange","blue","red","green"}}
  \newcount\cyclecount \cyclecount=-1
  \newcount\ind \ind=-1
  \begin{tikzpicture}[nodes = {font=\sffamily}]
    \foreach \percent/\name in {
      8/C++,8/Linux,7/Arduino,6/Python,6/Erlang,5/H5
    } {
      \ifx\percent\empty\else               % If \percent is empty, do nothing
      \global\advance\cyclecount by 1     % Advance cyclecount
      \global\advance\ind by 1            % Advance list index
      \ifnum3<\cyclecount                 % If cyclecount is larger than list
      \global\cyclecount=0              %   reset cyclecount and
      \global\ind=0                     %   reset list index
      \fi
      \pgfmathparse{\cyclelist[\the\ind]} % Get color from cycle list
      \edef\color{\pgfmathresult}         %   and store as \color
      % Draw angle and set labels
      \draw[fill={\color!50},draw={\color}] (0,0) -- (\angle:\radius) arc (\angle:\angle+\percent*1.8*2.5:\radius) -- cycle;
      \node at (\angle+0.5*\percent*1.8*2.5:0.7*\radius) {\name};
      \pgfmathparse{\angle+\percent*1.8*2.5}  % Advance angle
      \xdef\angle{\pgfmathresult}         %   and store in \angle
      \fi
    };
  \end{tikzpicture}%
}

\clearpage
\end{document}

However, you really shouldn't use this code. For one thing it redefines \color in an environment which uses colours a lot. The redefinition is only local, but that still seems dubious. Moreover \name is serving as both a local variable and a macro taking arguments, which is confusing. And it is not obvious that the \global definitions are not going to wipe out something crucial, either.

Moreover, you don't need to do any of these dangerous things. The following should be considerably safer:

\documentclass[14pt,a4paper,san]{moderncv}
\moderncvstyle{classic}
\moderncvcolor{blue}
\name{a}{a}
\title{s}
\address{}{s}
\email{}
\phone[mobile]{1212}
\begin{document}

\cvitem{}{%
  \begin{tikzpicture}[font=\sffamily]
    % these are local - much less likely to cause problems
    \def\radius{3}
    \def\cyclelist{{"orange","blue","red","green"}}
    \foreach \percent/\pname [evaluate=\percent as \pangle using ((4.5*\percent)+\panglelast)) , remember=\pangle as \panglelast (initially 0), count=\cyclecount from 0] in 
    {
      8/C++,8/Linux,7/Arduino,6/Python,6/Erlang,5/H5
    } {
      \pgfmathsetmacro\mycolor{\cyclelist[(int(mod(\cyclecount,4)))]}
      % Draw angle and set labels
      \draw [fill={\mycolor!50}, draw={\mycolor}] (0,0) -- (\panglelast:\radius) arc (\panglelast:\pangle:\radius) -- cycle;
      \node at ({(\pangle+\panglelast)/2}:0.7*\radius) {\pname};
    };
  \end{tikzpicture}%
}

\end{document}

and produces exactly the same result (except that I've lost the label of the \cvitem somewhere along the line.

To de-squish the labels, you might also prefer something which looks more like the following:

\documentclass[14pt,a4paper,san]{moderncv}
\moderncvstyle{classic}
\moderncvcolor{blue}
\name{a}{a}
\title{s}
\address{}{s}
\email{}
\phone[mobile]{1212}
\begin{document}

\cvitem{}{%
  \begin{tikzpicture}[font=\sffamily]
    % these are local - much less likely to cause problems
    \def\radius{3}
    \def\cyclelist{{"orange","blue","red","green"}}
    \foreach \percent/\pname [evaluate=\percent as \pangle using ((4.5*\percent)+\panglelast)) , remember=\pangle as \panglelast (initially 0), count=\cyclecount from 0] in 
    {
      8/C++,8/Linux,7/Arduino,6/Python,6/Erlang,5/H5
    } {
      \pgfmathsetmacro\mycolor{\cyclelist[(int(mod(\cyclecount,4)))]}
      % Draw angle and set labels
      \draw [fill={\mycolor!50}, draw={\mycolor}] (0,0) -- (\panglelast:\radius) arc (\panglelast:\pangle:\radius) -- cycle;
      \path (0,0) -- ({(\pangle+\panglelast)/2}:\radius) node [midway, sloped] {\pname};
    };
  \end{tikzpicture}%
}

\end{document}