引用投影機投影片編號並未顯示所有投影片（未定義的參考錯誤）

Question

我有一張逐漸打開的幻燈片。假設它通常有 n 張幻燈片。但「現在」我決定不再從投影片 1 開始，而是從投影片 2 開始。我該如何解決這個問題？

我在下面提供了一個最小的例子。請注意，我複製了所有幻燈片，以便我可以將標籤定義為幻燈片的參數以及「通常的方式」——只是為了表明這不會改變任何內容。

這裡是程式碼：

\documentclass{beamer}

\begin{document}

\begin{frame}<2->{Title of Slide 1}\label{LabelOfSlideOne}
  Slide 1 has three subslides, opened one by one, normally. Here, however, we start at slide number 2!
  \begin{itemize}[<+->]
    \item 1
    \item 2
    \item 3
  \end{itemize}
\end{frame}


\begin{frame}<2->[label=LabelOfSlideTwo]{Title of Slide 2}
  Slide 2 is exactly as slide 1, we simply define the label differently.
  \begin{itemize}[<+->]
    \item 1
    \item 2
    \item 3
  \end{itemize}
\end{frame}


\begin{frame}{Title of Slide 3}\label{LabelOfSlideThree}
  Slide 3 has two subslides, we show them incrementally, as normal.
  \begin{itemize}[<+->]
    \item 1
    \item 2
  \end{itemize}
\end{frame}


\begin{frame}[label=LabelOfSlideFour]{Title of Slide 4}
  Slide 4 is exactly as slide 3, we simply define the label differently.
  \begin{itemize}[<+->]
    \item 1
    \item 2
  \end{itemize}
\end{frame}


\begin{frame}{Slide 5: Test all the references!}
  \begin{itemize}
    \item This should show a 1: \ref{LabelOfSlideOne}
    \item This should show a 2: \ref{LabelOfSlideTwo}
    \item This should show a 3: \ref{LabelOfSlideThree}
    \item This should show a 4: \ref{LabelOfSlideFour}
  \end{itemize}
\end{frame}

\end{document}

這就是結果：

這表明雖然通常情況下定義標籤效果很好（最後兩張投影片），當我們不顯示所有投影片（前兩張投影片）時，它就不起作用。

那麼...如何解決這個問題呢？

Answer 1

有幾種方法可以避免該問題：

• 您可以在特定覆蓋層上指定標籤，例如\label<2>{LabelOfSlideOne}

• 您可以引用標籤的特定覆蓋層，例如\ref{LabelOfSlideTwo<2>}

---

\documentclass{beamer}

\begin{document}

\begin{frame}<2->{Title of Slide 1}\label<2>{LabelOfSlideOne}
  Slide 1 has three subslides, opened one by one, normally. Here, however, we start at slide number 2!
  \begin{itemize}[<+->]
    \item 1
    \item 2
    \item 3
  \end{itemize}
\end{frame}


\begin{frame}<2->[label=LabelOfSlideTwo]{Title of Slide 2}
  Slide 2 is exactly as slide 1, we simply define the label differently.
  \begin{itemize}[<+->]
    \item 1
    \item 2
    \item 3
  \end{itemize}
\end{frame}


\begin{frame}{Title of Slide 3}\label{LabelOfSlideThree}
  Slide 3 has two subslides, we show them incrementally, as normal.
  \begin{itemize}[<+->]
    \item 1
    \item 2
  \end{itemize}
\end{frame}


\begin{frame}[label=LabelOfSlideFour]{Title of Slide 4}
  Slide 4 is exactly as slide 3, we simply define the label differently.
  \begin{itemize}[<+->]
    \item 1
    \item 2
  \end{itemize}
\end{frame}


\begin{frame}{Slide 5: Test all the references!}
  \begin{itemize}
    \item This should show a 1: \ref{LabelOfSlideOne}
    \item This should show a 2: \ref{LabelOfSlideTwo<2>}
    \item This should show a 3: \ref{LabelOfSlideThree}
    \item This should show a 4: \ref{LabelOfSlideFour}
  \end{itemize}
\end{frame}

\end{document}