% 图1\documentclass{article}\usepackage{amsmath}\usepackage{tikz}\usetikzlibrary{calc}\usetikzlibrary{arrows.meta}\newcommand\xrightrightarrow[1]{\mathrel{\raisebox{0.4mm}{\!\!            \begin{tikzpicture}[>=stealth]            \node[inner sep=1ex] (a) {$\scriptstyle #1$};            \path[draw,<-] ($(a.south east)+(0,0)$) --($(a.south west)+(0,0)$);            \path[draw,<-] ($(a.south east)+(0,0.109)$) --($(a.south west)+(0,0.109)$);            \end{tikzpicture}}}}\begin{document}    \[A\xrightrightarrow{\quad I\quad}g(x)\]\end{document}

% 图2\documentclass[border=5pt]{standalone}\usepackage{tikz}\usepackage{mathtools}\usetikzlibrary{arrows}\usepackage{xparse}\NewDocumentCommand{\xrightleftarrow}{ O{}O{} }{%  \mathrel{%    \vcenter{      \hbox{%        \begin{tikzpicture}          \node[minimum width=0.75cm,align=center] (a){\text{\vphantom{hg}#1}\\[0.3ex]\vphantom{hg}#2};          \draw[-stealth] ([yshift=0.4ex]a.west) -- ([yshift=0.4ex]a.east);          \draw[stealth-] ([yshift=-0.4ex]a.west) -- ([yshift=-0.4ex]a.east);        \end{tikzpicture}      }    }%  }\!\!%}\begin{document}$A\xrightleftarrow B$ \quad$C\xrightleftarrow[some text here] D$ \quad$E\xrightleftarrow[][some text again] F$ \quad$G\xrightleftarrow[some ght][some text again] H$\end{document}

symbols-a4.pdf 其它宏包的长箭头