title: How to get File from R.raw
body: <p>I need to get an array of bytes of a File, so I need to know the length of the file. 
  How can I get a file from the assets or raw directory ? </p>
  
  <p>It seems that the most normal is to get the InputStream, but then can't get the length of the file.</p>
  
  <p>How can I File from R.raw ?</p>