# Have multiple overlay items at the same position

I want to have a list of items on a beamer slid which should appear one by one. For each item, I want to have a separate explanation block which should only be visible as the item appears. What I have is this code:

\begin{frame}
\begin{itemize}
\item<1-> Foo
\item<2-> Bar
\item<3-> Bla
\end{itemize}
\begin{block}{About Foo}<1>
...
\end{block}
\begin{block}{About Bar}<2>
...
\end{block}
\begin{block}{About Bla}<3>
...
\end{block}
\end{frame}


This does work, but my problem is, that the three blocks are below each other. They get their fixed position as if I was not using overlays and just get hidden.

What I want is the three blocks to be all on the same position (the one of the About Foo block). Is that possible?

## 1 Answer

You can warp your blocks in onlyenv to get the desired result:

\documentclass{beamer}

\begin{document}

\begin{frame}
\begin{itemize}[<+->]
\item Foo
\item Bar
\item Bla
\end{itemize}
\begin{onlyenv}<1>
\begin{block}{About Foo}
...
\end{block}
\end{onlyenv}
\begin{onlyenv}<2>
\begin{block}{About Bar}
...
\end{block}
\end{onlyenv}
\begin{onlyenv}<3>
\begin{block}{About Bla}
...
\end{block}
\end{onlyenv}
\end{frame}

\end{document}