Titlesec 命令被 frontmatter 阻止

Question

\frontmatter 阻止了 \titleformat 从序言传播到第一章。 有办法避免这种情况吗？

  \documentclass[11pt,A4]{book}
  \usepackage{titlesec}

  \titleformat{\chapter}[display]
  {\bfseries}{Title Above}{20pt}{\Huge}[\vspace{2ex}\titlerule\vspace{0.2ex}\titlerule]

  \begin{document}
  \chapter{Preface (before frontmatter)}
  \frontmatter% blocks the propagation of the titleformat to the first chapter
  \chapter{Chapter 1 (after frontmatter)}
  \end{document}  

仅当不存在 \frontmatter 时，才会显示第 1 章的上部标题。

Answer 1

这是更正后的代码，感谢以上所有评论。

  \documentclass[11pt,A4]{book}
  \usepackage{titlesec}

  \titleformat{\chapter}[display]
  {\normalfont\huge\bfseries}{Title Above}{20pt}{\Huge}[\vspace{2ex}\titlerule\vspace{0.2ex}\titlerule]

  \begin{document}
  \frontmatter
  \chapter{Preface (after frontmatter)}
  \mainmatter
  \chapter{Chapter 1 (with ``mainmatter")}
  \backmatter
  \chapter{Chapter after ``backmatter")}
  \end{document}