Tikz 树：如何向终端节点添加多条线以避免节点重叠

Question

我的树的终端节点的文本重叠了。有人知道如何将标签放在多行上吗？我查看了 stackoverflow，但没有找到解决方案。我可以将树隔开，但我更喜欢在节点上添加第二行，因为最终，间距只能这么大。

我尝试在文本中添加双反斜杠，但出现了错误消息。有人有什么建议吗？下面是我的代码和我正在尝试执行的操作的图像（之前和理想情况下之后）

谢谢。

\begin{tikzpicture} [scale=1.5] 
\tikzstyle{solid node} =[circle,draw,inner sep=1.5,fill=black]
\tikzstyle{hollow node}=[circle,draw,inner sep=1.5]
\tikzstyle{level 1}=[level distance=15mm,sibling distance=3.5cm]
\tikzstyle{level 2}=[level distance=15mm,sibling distance=2.5cm]
\tikzstyle{level 3}=[level distance=15mm,sibling distance=1cm]

\node(0)[hollow node,label=above:{},align=left]{} 
child{node[solid node]{}
    child{node[hollow node,label=below,align=left:{appleJacks are great \\ appleJacks are great}]{} edge from parent node[left]{a}}
    child{node[hollow node,label=below:{appleJacks are great, \\ appleJacks are great}]{} edge from parent node[right]{b}}
    edge from parent node[left,xshift=-5]{action1}
}
child{node[solid node]{}
    child{node[hollow node,label=below:{appleJacks are great, appleJacks are great}]{} edge from parent node[left]{a}}
    child{node[hollow node,label=below:{appleJacks are great, appleJacks are great}]{} edge from parent node[right]{b}}
    edge from parent node[right,xshift=5]{action2}
};
\draw[dashed, label=above right:{my label}](0-1)to(0-2);

\end{tikzpicture}

Answer 1

您需要在第 1 级增加兄弟距离：

\documentclass[margin=3mm]{standalone}
\usepackage{tikz}
\usetikzlibrary{quotes}


\begin{document}
    \begin{tikzpicture}[scale=1.5,
every label/.append style = {align=center},
 solid node/.style = {circle,draw,fill=black,inner sep=1.5pt},
hollow node/.style = {circle,draw,inner sep=1.5pt},
level distance = 15mm,
level 1/.style = {sibling distance=5cm},
level 2/.style = {sibling distance=2.5cm},
lbl/.style = {pos=0.55, anchor=south #1, font=\footnotesize},
                    ]
\node(0)[hollow node]{}
    child{node[solid node]{}
        child{node[hollow node,label=below:{appleJacks are great \\ appleJacks are great}] {}
             edge from parent node[lbl=east]{a}}
        child{node[hollow node,label=below:{appleJacks are great, \\ appleJacks are great}]{}
            edge from parent node[lbl=west]{b}}
        edge from parent node[lbl=east]{action1}
        }
    child{node[solid node]{}
        child{node[hollow node,label=below:{appleJacks are great,\\ appleJacks are great}]{} 
            edge from parent node[lbl=east]{a}}
        child{node[hollow node,label=below:{appleJacks are great,\\ appleJacks are great}]{} 
            edge from parent node[lbl=west]{b}}
        edge from parent node[lbl=west]{action2}
        };
\draw[dashed](0-1) to["my label"] (0-2);
    \end{tikzpicture}
\end{document}

附录：
如果您想要绘制具有更多级别的树，则使用该forest包会非常方便。上述树的代码可以写为Č

\documentclass[border=3.141592]{standalone}
\usepackage{forest}
\usetikzlibrary{arrows.meta, quotes}

\begin{document}
    \begin{forest}
for tree = {
% nodes
    circle, draw, minimum size=6pt, inner sep=0pt,
/tikz/N/.style = {rectangle, draw=none, 
                  font=\small\linespread{0.84}\selectfont,
                  inner ysep=4pt, inner xsep=0pt,
                  text width=8.8em, align=center
                 },
% tree
if level = 2{N, 
             child anchor=north,
             edge=-{Circle[open, length=6pt]} }
            {-},
   l sep = 12mm,
   s sep = 2mm,
%tier/.option = level,
%% edge labels
/tikz/ELS/.style = {% Edge Label Style
              pos=0.5, node font=\scriptsize,
              inner sep=2pt, anchor=south #1},
       EL/.style = {% Edge Label
            if n=1{edge label={node[ELS=east]{#1}}}
                  {edge label={node[ELS=west]{#1}}}},
           }
[   
    [ , fill, name=A, EL=action 1
        [appleJacks are great appleJacks are great,
         EL=$a$
        ]
        [appleJacks are great appleJacks are great,
         EL=$b$,
        ]
    ]
    [ , fill, name=B, EL=action 2
        [appleJacks are great appleJacks are great,
         EL=$a$,
        ]
        [appleJacks are great appleJacks are great,
         EL=$b$,
        ]
    ]
]
\draw[dashed]   (A) to [ELS, "my label"] (B);
    \end{forest}
\end{document}

您可以观察到，现在底层的节点是矩形（label在 MWE 上方替换），并且到这些节点的边的样式更改为edge=-{Circle[open, length=6pt]}。