In your example code you are using some keys which don't belong to mdframed
; numbers
, frame
, framesep
are keys for lstlistings
from the listings
package and not for mdframed
; with mdframed, you need frametitle
:
\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[framemethod=TikZ]{mdframed}
\mdfsetup{frametitlealignment=\center}
\begin{document}
\section{mdframed}
\begin{mdframed}[frametitle={The title of the frame}]
text
\end{mdframed}
\end{document}

After the edit to the original question, here's a possible solution:
\documentclass{article}
\usepackage{mdframed}
\usepackage{lipsum}
\newenvironment{myenv}[1]
{\mdfsetup{
frametitle={\colorbox{white}{\space#1\space}},
innertopmargin=10pt,
frametitleaboveskip=-\ht\strutbox,
frametitlealignment=\center
}
\begin{mdframed}%
}
{\end{mdframed}}
\begin{document}
\begin{myenv}{The frame title}
\lipsum[2]
\end{myenv}
\end{document}

\mdfsetup{frametitlealignment=\center}
might help.:)
– Paulo Cereda Aug 28 '12 at 15:08mdframed
(numbers
,frame
,framesep
); those are keys forlstlistings
from thelistings
package and not formdframed
. – Gonzalo Medina Aug 28 '12 at 15:20