在投影仪幻灯片上的 itemize 和 enumerate 内围绕文本绘制一个圆圈

Question

我有以下定义演示文稿的单帧的代码beamer：

\begin{frame}{Focus on Merkel Cells}
  \begin{itemize}
  \item \textbf{1875}: Merkel cells discovered by Friedrich Merkel
  \item \textbf{1969}: Merkel cell-neurite complexes implicated in
    touch reception
  \item \textbf{1969-2014}: Unresolved debate
    \begin{enumerate}
      \item A$\beta$ SAI neurons are mechanoreceptive (analagous to
        olfaction and all other LTMRs)
      \item Merkel cells are mechanoreceptive (analagous to taste and
        hearing)
      \item \alert{\textbf{Both are mechanoreceptive: A$\beta$ SAI rapid, Merkel
            sustained}}
      \end{enumerate}
    \item \textbf{2014}: Explosion of new evidence
  \end{itemize}
\end{frame}

我想在文本周围画一个空心黑色圆圈A$\beta$ SAI rapid,，并且不介意其他文本是否被遮住。我该怎么做？

Answer 1

tikzmark这是一个使用 TikZ及其fit库的 选项

\documentclass{beamer}
\usepackage{tikz}
\usetikzlibrary{tikzmark,fit}

\begin{document}

\begin{frame}{Focus on Merkel Cells}
  \begin{itemize}
  \item \textbf{1875}: Merkel cells discovered by Friedrich Merkel
  \item \textbf{1969}: Merkel cell-neurite complexes implicated in
    touch reception
  \item \textbf{1969-2014}: Unresolved debate
    \begin{enumerate}
      \item A$\beta$ SAI neurons are mechanoreceptive (analagous to
        olfaction and all other LTMRs)
      \item Merkel cells are mechanoreceptive (analagous to taste and
        hearing)
      \item \alert{\textbf{Both are mechanoreceptive: \tikzmark{start}A$\beta$ SAI rapid\tikzmark{end}, Merkel
            sustained}}
      \end{enumerate}
    \item \textbf{2014}: Explosion of new evidence
  \end{itemize}
\begin{tikzpicture}[remember picture,overlay]
\node<2>[draw,line width=2pt,cyan,circle,fit={(pic cs:start) (pic cs:end)}] {};
\end{tikzpicture}  
\end{frame}

\end{document}

结果（对圆圈编译两到三次即可到达其最终位置）：

由于 TikZ 和beamer合作，您可以使用叠加层，例如，

\node<2>[draw,line width=2pt,cyan,circle,fit={(pic cs:start) (pic cs:end)}] {};

这样圆圈就会出现在第二张幻灯片上。

使用椭圆（需要shapes.geometric库）：

\documentclass{beamer}
\usepackage{tikz}
\usetikzlibrary{tikzmark,fit,shapes.geometric}

\begin{document}

\begin{frame}{Focus on Merkel Cells}
  \begin{itemize}
  \item \textbf{1875}: Merkel cells discovered by Friedrich Merkel
  \item \textbf{1969}: Merkel cell-neurite complexes implicated in
    touch reception
  \item \textbf{1969-2014}: Unresolved debate
    \begin{enumerate}
      \item A$\beta$ SAI neurons are mechanoreceptive (analagous to
        olfaction and all other LTMRs)
      \item Merkel cells are mechanoreceptive (analagous to taste and
        hearing)
      \item \alert{\textbf{Both are mechanoreceptive: A\tikzmark{start}$\beta$ SAI rapi\tikzmark{end}d, Merkel
            sustained}}
      \end{enumerate}
    \item \textbf{2014}: Explosion of new evidence
  \end{itemize}
\begin{tikzpicture}[remember picture,overlay]
\node[draw,line width=2pt,cyan,ellipse,inner ysep=15pt,fit={(pic cs:start) (pic cs:end)}] {};
\end{tikzpicture}  
\end{frame}

\end{document}