title: file.length return always 0 in android
body: <p>I want to check size of file where I have only URI <code>content://media/external/video/media/813</code>
  to get size of file I use:</p>
  
  <pre><code>File file=new File(uri.getPath());
                      long ls = file.length();
  </code></pre>
  
  <p>and always get 0. Any ideas?</p>