如何使用套印而不添加额外空间？

Question

我尝试使用套印在同一张幻灯片上显示不同的内容。不幸的是，这会增加一些额外的空间。我该如何避免这种情况？

以下是一个例子：

\documentclass{beamer}

\begin{document}

\begin{frame}{Frame 1}
  \begin{itemize}
    \item Here the space below this line is smaller ...
    \item Following line 1
  \end{itemize}
\end{frame}

\begin{frame}{Frame 2}
  \begin{itemize}
    \item ... than below here
  \end{itemize}
  \begin{overprint}
    \onslide<1> 
    \begin{itemize}
      \item Following line 2.1
    \end{itemize}
    \onslide<2> 
    \begin{itemize}
      \item Following line 2.2
    \end{itemize}
  \end{overprint}
\end{frame}

\end{document}

编辑

这里有另一个例子来表明额外的空间不是（仅仅？）来自于关闭 itemize。

\documentclass{beamer}

\begin{document}

\begin{frame}{Test 1}
  Here the space below this line is smaller ...
  \begin{itemize}
    \item Following line 1
  \end{itemize}
\end{frame}

\begin{frame}{Test 2}
  ... than below here
  \begin{overprint}
    \onslide<1> 
    \begin{itemize}
      \item Following line 2.1
    \end{itemize}
    \onslide<2> 
    \begin{itemize}
      \item Following line 2.2
    \end{itemize}
  \end{overprint}
\end{frame}

\end{document}

Answer 1

额外的空间 - 至少部分 - 不是由套印引起的，而是由关闭和打开新itemize环境引起的，您可以使用以下方法进行测试

\documentclass{beamer}

\begin{document}

\begin{frame}{Frame 1}
  \begin{itemize}
    \item Here the space below this line is smaller ...
    \item Following line 1
  \end{itemize}
\end{frame}

\begin{frame}{Frame 2}
  \begin{itemize}
    \item ... than below here
  \end{itemize}
  \begin{itemize}
      \item Following line 2.1
   \end{itemize}
\end{frame}

\end{document}

如果您不需要单独的 itemize 环境，我只需使用一个环境：

\documentclass{beamer}

\begin{document}

\begin{frame}{Frame 1}
  \begin{itemize}
    \item Here the space below this line is smaller ...
    \item Following line 1
  \end{itemize}
\end{frame}

\begin{frame}{Frame 2}
  \begin{itemize}
    \item ... than below here
    \only<1>{\item Following line 2.1}
    \only<2>{\item Following line 2.2}
   \end{itemize}
\end{frame}

\end{document}