title: How to redraw a part of surfaceview android
body: <p>I used <code>surfaceview</code> to create a graph. This graph changes continuously over time. </p>
  
  <p>When I use <code>postInvalidate</code> method to update graph, <code>surfaceview</code> is redrawn but I don't want to redraw xy-axis. what should I do?</p>