如何在目录中仅显示一次章节名称

Question

考虑一下这个MWE：

\documentclass[aspectratio=169]{beamer}
\usetheme{Madrid}
\setbeamertemplate{caption}[numbered]
\usepackage{animate}
\mode<presentation> {
    \usepackage[font=footnotesize,labelfont=bf]{caption}
    \usepackage{booktabs}
    \usepackage{ragged2e}
    \usepackage{xcolor}
    \usepackage{multirow}
    \usefonttheme{serif}    
    \usecolortheme{beaver}
    \usepackage{blindtext}
    \usepackage{pdflscape}
    
}
\newenvironment{myitemize}{%
    \begingroup
    \setbeamercolor{itemize item}{parent=structure}
    \setbeamercolor{alerted text}{fg=black}
    \setbeamercolor{itemize/enumerate body}{fg=white}
    \begin{itemize}[<alert@+->]
    }{
    \end{itemize}
    \endgroup
}

\begin{document}
    \begin{frame}
        \titlepage
    \end{frame}
    \begin{frame}
        \frametitle{Outline}
        \tableofcontents 
    \end{frame}
    

    \begin{frame}
    \section{Introduction}  
    \frametitle{Introduction}
    
    \justifying
    
    \vspace{0.5cm}
    
    \textbf{XX}\\
    
    \vspace{0.5cm}
    \begin{myitemize}
        \justifying
        \only<1->{\item x1} 
        \only<2->{\item x2} 
        \only<3->{\item x3}
    \end{myitemize}
\end{frame}


    \begin{frame}
    \centering
    \Huge
    \textbf{\textcolor{blue}{THANK YOU}}
\end{frame}

\end{document} 

目录中的章节标题“简介”出现了三次。如何让它只显示一次？

Answer 1

分段命令（例如\sectionalways）需要在环境之外使用frame。切勿将它们放在框架内。

\documentclass[aspectratio=169]{beamer}
\usetheme{Madrid}
\setbeamertemplate{caption}[numbered]
\usepackage{animate}
\mode<presentation> {
    \usepackage[font=footnotesize,labelfont=bf]{caption}
    \usepackage{booktabs}
    \usepackage{ragged2e}
%    \usepackage{xcolor}
    \usepackage{multirow}
    \usefonttheme{serif}    
    \usecolortheme{beaver}
    \usepackage{blindtext}
    \usepackage{pdflscape}
    
}
\newenvironment{myitemize}{%
    \begingroup
    \setbeamercolor{itemize item}{parent=structure}
    \setbeamercolor{alerted text}{fg=black}
    \setbeamercolor{itemize/enumerate body}{fg=white}
    \begin{itemize}[<alert@+->]
    }{
    \end{itemize}
    \endgroup
}

\begin{document}
    \begin{frame}
        \titlepage
    \end{frame}
    \begin{frame}
        \frametitle{Outline}
        \tableofcontents 
    \end{frame}
    
    \section{Introduction}  
    \begin{frame}

    \frametitle{Introduction}
    
    \justifying
    
    \vspace{0.5cm}
    
    \textbf{XX}\\
    
    \vspace{0.5cm}
    \begin{myitemize}
        \justifying
        \only<1->{\item x1} 
        \only<2->{\item x2} 
        \only<3->{\item x3}
    \end{myitemize}
\end{frame}


    \begin{frame}
    \centering
    \Huge
    \textbf{\textcolor{blue}{THANK YOU}}
\end{frame}

\end{document}