我使用 Tikz 在矩阵上绘制一些特定的形状，这是我正在使用的 MWE：
\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{matrix,decorations.pathreplacing}
\pgfkeys{tikz/mymatrixenv/.style={decoration=brace,every left delimiter/.style={xshift=4pt},every right delimiter/.style={xshift=-4pt}}}
\pgfkeys{tikz/mymatrix/.style={matrix of math nodes,left delimiter=[,right delimiter={]},inner sep=1pt,row sep=0em,column sep=0em,nodes={inner sep=6pt}}}
\begin{document}
\begin{tikzpicture}[baseline=0cm,mymatrixenv]
\matrix [mymatrix,text width=0.6em,align=center] (m)
{
a & b & c \\
d & e & f \\
g & h & i \\
};
\pgfmathsetmacro{\offset}{0.5mm}
\draw [thick,blue,rounded corners=1mm] (m-1-1.west) |- (m-3-3.south) -- cycle;
\draw [thick,red,rounded corners=1mm] (m-1-1.north) -| (m-3-3.east) -- cycle;
\draw [thick,green,rounded corners=1mm] ([yshift=\offset]m-1-1.west) -- ([xshift=-\offset]m-1-1.north) -- ([yshift=-\offset]m-3-3.east) -- ([xshift=\offset]m-3-3.south) -- cycle;
\end{tikzpicture}
\end{document}
结果：
但是当我在 Beamer 演示文稿（主题：华沙）中尝试此代码时，我得到了以下信息：
出了什么问题？我该如何修复？
答案1
您需要使用一个fragile框架：
\documentclass{beamer}
\usepackage{tikz}
\usetikzlibrary{matrix,decorations.pathreplacing}
\pgfkeys{tikz/mymatrixenv/.style={decoration=brace,every left delimiter/.style={xshift=4pt},every right delimiter/.style={xshift=-4pt}}}
\pgfkeys{tikz/mymatrix/.style={matrix of math nodes,left delimiter=[,right delimiter={]},inner sep=1pt,row sep=0em,column sep=0em,nodes={inner sep=6pt}}}
\begin{document}
\begin{frame}[fragile]
\begin{tikzpicture}[baseline=0cm,mymatrixenv]
\matrix [mymatrix,text width=0.6em,align=center] (m)
{
a & b & c \\
d & e & f \\
g & h & i \\
};
\pgfmathsetmacro{\offset}{0.5mm}
\draw [thick,blue,rounded corners=1mm] (m-1-1.west) |- (m-3-3.south) -- cycle;
\draw [thick,red,rounded corners=1mm] (m-1-1.north) -| (m-3-3.east) -- cycle;
\draw [thick,green,rounded corners=1mm] ([yshift=\offset]m-1-1.west) -- ([xshift=-\offset]m-1-1.north) -- ([yshift=-\offset]m-3-3.east) -- ([xshift=\offset]m-3-3.south) -- cycle;
\end{tikzpicture}
\end{frame}
\end{document}
