TikZ 每条虚线上都有箭头

Question

我想在 TikZ 中创建虚线，每条虚线的末端都有一个箭头。以下代码使用 \foreach 循环实现此目的，但正在寻找一种使用样式键来实现此目的的方法。类似于

\draw [densely dashed, ->] (0,0) -- ++(100pt,0);

但将箭头放在所有破折号上而不仅仅是末端。

梅威瑟：

\documentclass[12pt]{article}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
    \draw [densely dashed] (0,0) -- ++(100pt,0);
    \foreach \i in {0,5,10,...,100}{%
        \draw [->] (\i*1pt,-0.25) -- ++(3pt,0);
    }
\end{tikzpicture}
\end{document}

Answer 1

我想对于这个最简单的可能性之一就是采用decorations.markings。

\documentclass[12pt]{article}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}
\begin{document}
\begin{tikzpicture}
    \draw [dash pattern=on 3pt off 2pt,postaction={decorate,
    decoration={markings,
    mark=between positions 3pt and 1 step 5pt with {\arrow{>};}}}] (0,0) -- ++(100pt,0);
\end{tikzpicture}
\end{document}

根据实际应用，可以将其设为样式，或者，对于弯曲路径来说，更好的方法是声明一个新的（元）装饰。幸运的是，pgfmanual 在第 1007 页上有一个元装饰，只需稍微修改一下即可

\documentclass[tikz,border=3.14mm]{standalone}
\usetikzlibrary{decorations,arrows.meta}
\pgfdeclaremetadecoration{many arrows}{initial}{ 
\state{initial}[width=0pt, next state=arrow] {
    \pgfmathdivide{100}{\pgfmetadecoratedpathlength}
    \let\factor\pgfmathresult
    %\pgfsetlinewidth{1pt}
    \pgfset{/pgf/decoration/segment length=4pt}
  }
  \state{arrow}[
switch if less than=\pgfmetadecorationsegmentlength to final, width=\pgfmetadecorationsegmentlength/3,
next state=end arrow]
  {
    \decoration{curveto}
    \beforedecoration
    {
      \pgfpathmoveto{\pgfpointmetadecoratedpathfirst}
} }
\state{end arrow}[width=\pgfmetadecorationsegmentlength/3, next state=move] {
    \decoration{curveto}
    \beforedecoration{\pgfpathmoveto{\pgfpointmetadecoratedpathfirst}}
    \afterdecoration
    {
      \pgfsetarrowsend{Latex[length=1pt,width=1pt]}
      \pgfusepath{stroke}
    }
}
\state{move}[width=\pgfmetadecorationsegmentlength/2, next state=arrow]{} \state{final}{}
}
\begin{document}
\begin{tikzpicture}
\draw[ultra thin,decorate,decoration={many arrows,meta-segment length=3pt}] (0,0) .. controls (0,2) and (3,2) .. (3,0)
        .. controls (3,-2)  and (0,-2)  .. (0,-4)
        .. controls (0,-6)  and (3,-6)  .. (3,-8)
        .. controls (3,-10) and (0,-10) .. (0,-8);
\end{tikzpicture}       
\end{document}      

这里我放大了结果以显示箭头很小。（回想一下，直径是 3 厘米。）