Find biggest bounding box in a tikzpicture in beamer and then fix it.

testbb.tex

\documentclass{beamer}

\usepackage[utf8]{inputenc}

\usepackage{tikz}
\usetikzlibrary{arrows,overlay-beamer-styles,calc}

\makeatletter
% Thanks to Paul Gaborit https://tex.stackexchange.com/a/179946/38080
\def\extractcoord#1#2#3{
  \path let \p1=(#3) in \pgfextra{
    \pgfmathsetmacro#1{\x{1}/\pgf@xx}
    \pgfmathsetmacro#2{\y{1}/\pgf@yy}
    \xdef#1{#1} \xdef#2{#2}
  };
}
\makeatother
\newcommand{\showboundingbox}{%
    %
    % Show the bounding box of the tikzpicture. Use as last command.
    % It will not change the bounding box thanks to the overlay option.
    %
    \extractcoord\xa\ya{current bounding box.south west}
    \extractcoord\xb\yb{current bounding box.north east}
    \node [overlay, draw=red, fill=white, opacity=0.8, font=\tiny\ttfamily, anchor=north east] at (current bounding box.north east) {(\xa, \ya) (\xb, \yb)};
}

\begin{document}

% mode 1; it will jump.  
\begin{frame}
    \frametitle{jumping}
    \begin{center}
        \begin{tikzpicture}[>=stealth',thick]
            \node at (0,0) (1) {$1$};
            \node at (2,0) (2) {$2$};
            \draw<2-> (1) edge[bend left,->] (2);
            \draw<3-> (2) edge[bend left,->] (1);
            % print how much is big this picture (it will change every overlay)
            \showboundingbox
        \end{tikzpicture}
    \end{center}
\end{frame}


%%% note down the biggest coordinates and add a
%%% path to use as bounding box (I normally use a bit bigger
%%% one that what I found

\begin{frame}
    \frametitle{jumping}
    \begin{center}
        \begin{tikzpicture}[>=stealth',thick]
            \path [use as bounding box] (-0.25,-0.45) rectangle (2.25,0.45);
            \node at (0,0) (1) {$1$};
            \node at (2,0) (2) {$2$};
            \draw<2-> (1) edge[bend left,->] (2);
            \draw<3-> (2) edge[bend left,->] (1);
            % \showboundingbox %not needed anymore
        \end{tikzpicture}
    \end{center}
\end{frame}

\end{document}