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如何避免覆盖层跳跃

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如何避免覆盖层跳跃

我想在方程式下方写一些文本，点击后文本会发生变化。请考虑以下示例

\documentclass[12pt, a4paper,xcolor=dvipsnames]{beamer}

\begin{document}

\begin{frame}

\begin{align*}
a^2+b^2=c^2
\end{align*}

\only<1> {Some text on the first Slide, \\ 
that explains some things \\
and some more text}

\only<2> {Some other text on second Slide, \\ 
which is slightly shorter}

\end{frame}


\end{document}

在第二张幻灯片中，由于文本较短，公式向下跳动。如何避免这种情况？

答案1

您可以使用overlayarea环境来停止幻灯片中文本的抖动。以下语法和文档取自 Beamer 用户指南。

\begin{overlayarea}{⟨area width⟩}{⟨area height⟩}
⟨environment contents⟩
\end{overlayarea}

环境中的所有内容都将放置在指定大小的矩形区域中。无论其实际内容如何，​​该区域在帧的所有幻灯片上都将具有相同的大小。

对于您的示例，以下内容将起作用：

\documentclass[12pt, a4paper,xcolor=dvipsnames]{beamer}

\begin{document}

    \begin{frame}

        \begin{align*}
        a^2+b^2=c^2
        \end{align*}

        \begin{overlayarea}{\linewidth}{0.5\textheight}
        \only<1> {Some text on the first Slide, \\ 
            that explains some things \\
            and some more text}

        \only<2> {Some other text on second Slide, \\ 
            which is slightly shorter}
        \end{overlayarea}

    \end{frame}


\end{document}

这样会生成文本不会跳动的 pdf。

答案2

改用\onslide；它在不可见时保留空间。

    \onslide<1> {Some text on the first Slide, \\ 
        that explains some things \\
        and some more text}

    \onslide<2> {Some other text on second Slide, \\ 
        which is slightly shorter}

答案3

一种方法是使用相同的垂直空间（使用包）使<only>命令的文本开始和结束calc。请注意，这种方式也需要开始 \vspace添加一些非常长的文本或方程式。

\documentclass[12pt, a4paper,xcolor=dvipsnames]{beamer}
\usepackage{calc}
\newdimen\mycurrentheight
\newdimen\mymaxheight
\newdimen\myspace
\newdimen\zerodimen
\newsavebox{\mybox}

\def\keepHeight#1{
\setbox\mybox\vbox{#1}
\setlength{\mycurrentheight}{\ht\mybox+\dp\mybox}
\addspace{\mycurrentheight}
\usebox{\mybox}
\vskip \myspace
}


\def\addspace#1{
\ifdim\mycurrentheight>#1
\let\mymaxheight=\mycurrentheight
\let\myspace=\zerodimen
\else
\let\myspace=\zerodimen
\advance \myspace by \mymaxheight
\advance \myspace by -\mycurrentheight
\fi
}

\begin{document}

\begin{frame}

\vspace*{-50pt}
\begin{align*}
a^2+b^2=c^2
\end{align*}

    \only<1> {\keepHeight{ Some text on the first Slide, \\ 
        that explains some things \\
        and some more text}}

    \only<2> {\keepHeight{ Some other text on second Slide, \\ 
        which is slightly shorter}}

    \only<3> {\keepHeight{Some text on the third Slide, \\ 
        that explains some things \\
        and some more text and an equation \[x=4-7\]
        using much more space than the previous.}}

    \only<4> {\keepHeight{ Some other text on fourth Slide, \\ 
        which is  shorter}}

   \only <5> {Here we don't keep the height}
\end{frame}

除最后一帧之外的每一帧的结果都是完美“垂直对齐”的。

答案4

你可以使用一个技巧。添加 \phantom{some text} 来获得所需的行为。

\documentclass[12pt, a4paper,xcolor=dvipsnames]{beamer}

\begin{document}

\begin{frame}

\begin{align*}
a^2+b^2=c^2
\end{align*}

\only<1> {Some text on the first Slide, \\ 
that explains some things \\
and some more text}

\only<2> {Some other text on second Slide, \\ 
which is slightly shorter \\
\phantom{bla}}

\end{frame}


\end{document}

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