\tabular 多列无对齐

Question

我不知道哪里出了问题。无论如何，pdf 看起来还不错

\documentclass[a4paper,12pt]{book}
\usepackage[margin=1.5cm]{geometry}
\usepackage{colortbl}
\usepackage{multicol}
\everymath=\expandafter{\the\everymath\displaystyle}
\renewcommand{\arraystretch}{2.2}

\begin{document}

 \begin{tabular}{|m{0.55 \textwidth}|m{0.35 \textwidth}|}
   \hline
   \multicolumn{2}{|c|}{\rowcolor[gray]{0.8} {oscillations}} \\
   \hline
   \hline
   $T = \frac{1}{f} $ & $ T=\frac{\Delta t}{N}$ \\
   \hline
 \end{tabular}

\end{document}

我用 xelatex 编译后

This is XeTeX, Version 3.1415926-2.2-0.9995.2 (TeX Live 2009/Debian)
entering extended mode
(./test.tex
LaTeX2e <2009/09/24>
Babel <v3.8l> and hyphenation patterns for english, usenglishmax, dumylang, noh
yphenation, ibycus, monogreek, greek, ancientgreek, loaded.
(/usr/share/texmf-texlive/tex/latex/base/book.cls
Document Class: book 2007/10/19 v1.4h Standard LaTeX document class
(/usr/share/texmf-texlive/tex/latex/base/bk12.clo))
(/home/karathan/texmf/tex/latex/geometry/geometry.sty
(/usr/share/texmf-texlive/tex/latex/graphics/keyval.sty)
(/usr/share/texmf-texlive/tex/generic/oberdiek/ifpdf.sty)
(/usr/share/texmf-texlive/tex/generic/oberdiek/ifvtex.sty)
(/usr/share/texmf-texlive/tex/generic/ifxetex/ifxetex.sty)
(/usr/share/texmf-texlive/tex/xelatex/xetexconfig/geometry.cfg))
(/usr/share/texmf-texlive/tex/latex/colortbl/colortbl.sty
(/usr/share/texmf-texlive/tex/latex/tools/array.sty)
(/usr/share/texmf-texlive/tex/latex/graphics/color.sty
(/etc/texmf/tex/latex/config/color.cfg)
(/usr/share/texmf-texlive/tex/xelatex/xetex-def/xetex.def)))
(/usr/share/texmf-texlive/tex/latex/tools/multicol.sty) (./test.aux)


**... here is the problem**

*geometry* detected driver: pdftex
! Misplaced \noalign.
\rowcolor ->\noalign
                     {\ifnum 0=`}\fi \global \let \CT@do@color \CT@@do@color... 
l.12 ...{|c|}{\rowcolor[gray]{0.8} {oscillations}} 
                                                   \\ 
? [1] (./test.aux) ) 
Output written on test.pdf (1 page). 
Transcript written on test.log. 

Answer 1

里面\multicolumn已经太晚了，\rowcolor改变那个\cellcolor应该没问题。

Answer 2

放在\rowcolor[gray]{0.8}之前\multicolumn{2}{|c|}{oscillations}。

\documentclass[a4paper,12pt]{book}
\usepackage[margin=1.5cm]{geometry}
\usepackage{colortbl}
\usepackage{multicol}
\everymath=\expandafter{\the\everymath\displaystyle}
\renewcommand{\arraystretch}{2.2}
\begin{document}

 \begin{tabular}{|m{0.55 \textwidth}|m{0.35 \textwidth}|}
   \hline
   \rowcolor[gray]{0.8}\multicolumn{2}{|c|}{oscillations} \\
   \hline
   \hline
   $T = \frac{1}{f} $ & $ T=\frac{\Delta t}{N}$ \\
   \hline
 \end{tabular}

\end{document}