mdframed causes “too many floats” error

Question

I defined a new environemnt examples for a book I am writing. I would like examples to be with a framed grey box, and use the following construct

%----------------------------------------------------------------------------
% EXAMPLES
%----------------------------------------------------------------------------
\newlistof[chapter]{examples}{exp}{\listexamples}
\newcommand{\bex}[1]{%
\begin{mdframed}[linewidth=2, leftmargin=0, rightmargin=0, backgroundcolor=gray, linecolor=black, splittopskip=\topskip, skipbelow=\baselineskip, skipabove=\baselineskip]
\refstepcounter{examples}
\par\noindent\sqrblt\underline{\textbf{Example \theexamples. #1}}
\addcontentsline{exp}{examples}
{\protect\numberline{\theexamples}#1}\par}
\cftsetindents{examples}{0em}{2em} % for example numbers which are greater than 9
% Solution
\newcommand{\sol}{\begin{center}\underline{{\bf Solution:}}\end{center}}
% End of Example
\newcommand{\eex}{
\noindent \hbox{~~}\hfill \hbox{~~} \sqrblt
\end{mdframed}
}

If I activate the mdframed, I get "not in outer par mode". If I comment the mdframed part, all is well

Answer 1

Here is a solution which works.

Your feedback is welcome.

\setcounter{errorcontextlines}{999}
\documentclass[openany]{book}
\usepackage{amsmath}
\usepackage{xcolor}
\usepackage[framemethod=default]{mdframed}
\usepackage{tocloft}
%----------------------------------------------------------------------------
% EXAMPLES
%----------------------------------------------------------------------------
\newlistof[chapter]{examples}{exp}{\listexamples}
\cftsetindents{examples}{0em}{2em}
\newcommand*\listexamples{List of Examples}

\newcommand{\sqrblt}{\rule{0.1in}{0.1in}\hspace{.05in}}

\mdfdefinestyle{example}{%
   linewidth=2,
   leftmargin=0,
   rightmargin=0,
   backgroundcolor=gray,
   linecolor=black,
   splittopskip=\topskip,
   skipbelow=\baselineskip,
   skipabove=\baselineskip,
   frametitlefont=\bfseries,}

\newenvironment{examplesenv}[1]%
   {\refstepcounter{examples}%
    \addcontentsline{exp}{examples}{\protect\numberline{\theexamples}#1}
    \begin{mdframed}[style=example,frametitle={\sqrblt Example \theexamples.~#1}]
   }{\mbox{}\hspace{0.2in}\mbox{}\hfill\llap{\sqrblt}\end{mdframed}}

\let\bex\examplesenv
\let\eex\endexamplesenv

\usepackage{showframe,lipsum}
\begin{document}
\listofexamples
\chapter{foo}
\lipsum[1]

\begin{examplesenv}{Example one}
\lipsum[1]
\end{examplesenv}
\clearpage
\bex{Example two}
\lipsum[1]
\eex
\end{document}

EDIT

In a comment zampano wrote he insert a floating environment. This can't work. The explanation if given in the UK List of TeX Frequently Asked Questions

This is of course a contradiction: figure and table are designed to float, and will always have the potential to appear away from where you asked for them. Therefore you have to find a means of getting the caption and other effects without allowing the figure or table to float.

To use captions in this contents I prefer the method captionof (provided by the KOMA-script or by the packages caption or capt-of)

\begin{center}
 \includegraphics{picture}
  \captionof{figure}{foo}
\end{center}