Beamer 奇偶变化逐项列举

Question

我想自动获得以下效果

\documentclass{beamer}

\definecolor{color1}{RGB}{255,0,0}
\definecolor{color2}{RGB}{0,255,0}

\begin{document}
\begin{frame}
\begin{itemize}
\setbeamercolor{itemize item}{fg=color1}
\item
\setbeamercolor{itemize item}{fg=color2}
\item
\setbeamercolor{itemize item}{fg=color1}
\item
\setbeamercolor{itemize item}{fg=color2}
\item
\end{itemize}
\end{frame}
\end{document}

Answer 1

我认为通过这种方法你可以实现它：

\documentclass{beamer}
\usepackage{etoolbox}

\definecolor{color1}{RGB}{255,0,0}
\definecolor{color2}{RGB}{0,255,0}

\newcounter{myitem}
\setcounter{myitem}{1}
\renewcommand<>{\item}[1]{\only#2{
\ifnumodd{\themyitem}{%true
\setbeamercolor{itemize item}{fg=color1}\stepcounter{myitem}
}{%false
\setbeamercolor{itemize item}{fg=color2}\stepcounter{myitem}
}
\beameroriginal{\item}{#1}}}

\begin{document}
\begin{frame}
\begin{itemize}
\item text
\item text
\item text
\item text
\end{itemize}
\end{frame}
\end{document}

图形结果：

改进

要激活或禁用替代项目着色，您可以采用如下技巧：

\documentclass{beamer}
\usepackage{etoolbox}

\definecolor{color1}{RGB}{255,0,0}
\definecolor{color2}{RGB}{0,255,0}

\newif\ifitemcolor % <= create a new conditional
\itemcolortrue %<= set it to true to activate the coloring

\newcounter{myitem}
\setcounter{myitem}{1}
\renewcommand<>{\item}[1][]{\only#2{
\ifitemcolor%
\ifnumodd{\themyitem}{%true
\setbeamercolor{itemize item}{fg=color1}\stepcounter{myitem}
}{%false
\setbeamercolor{itemize item}{fg=color2}\stepcounter{myitem}
}\fi%
\beameroriginal{\item}{#1}}}

\begin{document}
\begin{frame}
\begin{columns}
\begin{column}{0.48\textwidth}
\itemcolorfalse %<= set it to false to disable the coloring
\begin{itemize}
\item
\item text
\item text
\item text
\end{itemize}
\end{column}
\begin{column}{0.48\textwidth}
\itemcolortrue %<= set it to true to re-activate the coloring
\begin{itemize}
\item 
\item text
\item text
\item text
\end{itemize}
\end{column}
\end{columns}
\end{frame}
\end{document}

在示例中，我创建了两个包含两个列表的列：左侧列表禁用了替代颜色，而右侧列表则未禁用。此外，使用附加项重新定义\item允许[]不插入文本，就像两个列表中的前两个元素一样。

图形结果为：

Answer 2

您还可以拥有两个定义，\item并在它们之间来回交替。交替着色是通过在环境\AlternateColors中调用来启用的itemize。如果没有这个，就会产生默认着色。

\documentclass{beamer}

\definecolor{color1}{RGB}{255,0,0}
\definecolor{color2}{RGB}{0,255,0}

\let\OldItem\item
\newcommand{\itemTwo}{%
    \setbeamercolor{itemize item}{fg=color2}\OldItem%
    \def\nextitem{\itemOne}%
}%
\newcommand{\itemOne}{%
    \setbeamercolor{itemize item}{fg=color1}\OldItem%
    \def\nextitem{\itemTwo}%
}%
\newcommand{\nextitem}{\itemOne}%
\newcommand*{\AlternateColors}{%
    \def\item{\nextitem}%
}%

\begin{document}
\begin{frame}
\begin{itemize}\AlternateColors% This enables the alternate coloring
  \item
  \item
  \item
  \item
\end{itemize}
\end{frame}
\end{document}