Latex: text should automatically fill the frame in Beamer slides

In beamer frames I want the contents to be spread out evenly across the frame.

Using option \documentclass[slidestop]{beamer} I can easily specify the contents to be top/center aligned but when I have only few bullets on a slide they get clustered together at the top, I want beamer to decide the spacing between them开发者_JAVA百科 automatically to spread them evenly.

Is this possible without putting vspace by trial and error?

I think using \vfill would reduce the trial and error part. One \vfill between each bullet should guarantee even spacing. Try \vfill before and/or after bullets to get separation from preceding text or from bottom of page. I don't use or know Beamer, but I suspect there's a way to put the \vfill commands into the Beamer template.

\documentclass{article}
\begin{document}
\begin{itemize}
\vfill\item This is text of first item
\vfill\item This is text of second item
\vfill\item This is text of third item
\end{itemize}
\end{document}

Per your comment, here's one way you could define vfill to be automatically used in main list items but have no vfill in subitems. THis way lets you use same \item command regardless of whether you're in main list or in nested list, but requires you to define or redefine environments, and to be aware of when you're adding a main (i.e, vfilled) list and when you're adding a non-vfilled (i.e, nested) list:

\documentclass{article}

\newenvironment{novfillenum}{\begin{enumerate}\let\item\olditem}%
{\end{enumerate}}
\newenvironment{vfilleditems}{\begin{itemize} \let\olditem\item \renewcommand\item{\vfill\olditem}}%
{\end{itemize}}

\begin{document}
\begin{vfilleditems}
\item Item One 
   \begin{novfillenum}
        \item subitem1
        \item s2
        \item s3
    \end{novfillenum}
\item Item Two 
   \begin{novfillenum}
        \item subitem1
        \item s2
        \item s3
    \end{novfillenum}
\item item three
   \begin{novfillenum}
        \item subitem1
        \item s2
        \item s3
    \end{novfillenum}
\end{vfilleditems}

\end{document}

Adding another sample here because first answer getting too crowded. Tested altering the label commands and, what do you know, it seems to work, sort of. It gives errors, though, which I'm sure are related to having the \vfill as part of the label construct. I'm surprised it does seem to create the desired output, but the method would need some tweaking to get it to work without errors:

\begin{document}

\let\oldlabelitemi\labelitemi
\renewcommand{\labelitemi}{\vfill\oldlabelitemi{\hspace{1ex}}}

\begin{itemize}

\item Item One 
    \begin{itemize}
    \item subone
    \item subtwo
    \item subthree
    \end{itemize}
\item Item Two 
   \begin{itemize}
        \item subitem1
        \item s2
        \item s3
    \end{itemize}
\item item three
   \begin{itemize}
        \item subitem1
        \item s2
        \item s3
    \end{itemize}
\end{itemize}

\end{document}