添加 tikzset 时形状消失

Question

考虑这个例子：

\documentclass[border=3.141592]{standalone}
\usepackage{tikz}
\usetikzlibrary{shapes.arrows}

\begin{document}
 \tikzset{
    rect/.style={
        font=\small,
    rectangle,
    rounded corners,
    minimum width=1em,
    text width=2em,
    %draw=blue!75,                                                                                                                                                                                     
    very thick,
    align=center,
    }%                                                                                                                                                                                                 
    }%                                                                                                                                                                                                     
\begin{tikzpicture}
  \draw [draw=black] (0.0, 0.0) rectangle (4.0, 4.0);                                                                                                                                                     
  %\tikz\draw[rect] (0.0, 0.0) rectangle (4.0, 4.0);
  \node[single arrow, draw=blue,
    minimum width = 1.0cm, single arrow head extend=1cm,
    minimum height = 2cm] at (2.0, 2.0)[anchor = center] {};
    \end{tikzpicture}
\end{document}

结果是：

然而，当我评论时

  \draw [draw=black] (0.0, 0.0) rectangle (4.0, 4.0); 

并取消注释

  %\tikz\draw[rect] (0.0, 0.0) rectangle (4.0, 4.0);

粗箭头的形状消失了：

怎么了？

Answer 1

正如您在评论中看到的那样，在环境\tikz中包含它不是一个好主意tikzpicture。您正在嵌套tikzpictures，这必然会产生错误。因此，只需删除该\tikz命令即可。

\documentclass[border=3.141592]{standalone}
\usepackage{tikz}
\usetikzlibrary{shapes.arrows}

\begin{document}
 \tikzset{
    rect/.style={
    font=\small,
    rectangle,
    rounded corners,
    minimum width=1em,
    text width=2em,
    %draw=blue!75,                                           
    very thick,
    align=center,
    }%                                           
    }%
                                                              
\begin{tikzpicture}
  % \draw [draw=black] (0.0, 0.0) rectangle (4.0, 4.0);
  \draw[rect] (0.0, 0.0) rectangle (4.0, 4.0);
  \node[single arrow, draw=blue,
    minimum width  = 1.0cm, single arrow head extend=1cm,
    minimum height = 2cm] at (2.0, 2.0)[anchor = center] {};
\end{tikzpicture}
\end{document}

Answer 2

大部分都是题外话（你的问题已经由@Juan Castaño 的回答解决了，+1）...

绘制矩形路径时使用的样式有点不寻常，而这通常用于节点。因此，我看到了两种绘制图片的可能方法：

\documentclass[border=3.141592]{standalone}
\usepackage{tikz}
\usetikzlibrary{fit,
                shapes.arrows}

 \tikzset{
   rect/.style = {rounded corners, very thick},
     SA/.style = {single arrow, draw=blue, thin, sharp corners,
                  minimum width=1.0cm, minimum height = 2cm,
                  single arrow head extend=1cm},
%%
    FIT/.style = {draw, rounded corners, very thick, inner sep=1cm,
                  fit=#1},
        } 

\begin{document}
% draw rectangle    
    \begin{tikzpicture}
\draw[rect] (0,0) rectangle (4, 4) node[SA, midway] {};
    \end{tikzpicture}

or 
 
% use of nodes
    \begin{tikzpicture}
\node[SA] (n1)  {};
\node[FIT=(n1)] {};
    \end{tikzpicture}
    
\end{document}