title: Supporting multiple screens on Android
body: <p>Have read the <a href="http://developer.android.com/guide/practices/screens_support.html" rel="nofollow">doc</a>  which is lengthy and still not clear.</p>
  
  <p>Assuming I have an image with size = 120px * 80px, under the default mdpi/160 density, I also need to prepare</p>
  
  <pre><code>ldpi = 90 * 60
  hdpi = 180 * 120
  xhdpi = 240 * 160
  </code></pre>
  
  <p>Are the calculation above right? Assume I only have a single layout, so what I need is to prepare the images and place them under the corresponding drawable folders, right?</p>
  
  <p>Thanks</p>