title: When is surfaceChanged activated?
body: <p>From <a href="http://developer.android.com/reference/android/view/SurfaceHolder.Callback.html" rel="noreferrer">the developer tutorial</a>, it writes:
  This is called immediately after any structural changes (format or size) have been made to the surface. You should at this point update the imagery in the surface. This method is always called at least once, after </p>
  
  <p>I do not know what situations refer to strucutral changes. How about screen orientation?</p>