您的操作方式与您链接的答案完全相同:
\documentclass{beamer}
\usetheme{AAUsidebar}
\setbeamercovered{invisible}
\setbeamercovered{%
again covered={\opaqueness<1->{15}}}
\begin{document}
\begin{frame}
\begin{itemize}[<+>]
\item Apple
\item Peach
\item Plum
\item Orange
\end{itemize}
\end{frame}
\end{document}