📅  最后修改于: 2022-03-11 14:59:34.177000             🧑  作者: Mango
\documentclass{article}
\usepackage{amsmath}
\makeatletter
\newcommand{\xLeftrightarrow}[2][]{\ext@arrow 0099\Leftrightarrowfill@{#1}{#2}}
\makeatother
\begin{document}
$A \xLeftrightarrow{\mathit{hello}} B$
\end{document}