title: Convert px to dp and sp in /values/dimen.xml in Android
body: <p>I know we should use dp/sp instead of px in UI design, but the UI designer I work with just gives me his design in pixels in 1280x720. 
  How should I convert the pixels in 1280x720 to dp/sp, and support multiple screens?</p>
  
  <p>I checked the doc, 30px in 1280x720 = 15dp in xhdpi. Should I make a <code>/values-xhdpi/dimen.xml</code> file in my project? And what about other resolutions? How should I deal with <code>ldpi</code>, <code>mdpi</code>, <code>hdpi</code>, <code>xxhdpi</code>, <code>xxxhdpi</code>?</p>
  
  <p>Also, I got the text sizes in pixels too. Do I need to do the same thing as I did with dp?</p>