title: Dip in xml does not work for different screen density in android simulator
body: <p>I'm testing multi dpi in android, and the layout xml file seems like this:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:orientation="vertical" android:layout_width="fill_parent"
      android:layout_height="fill_parent" android:background="@drawable/new_album_bg"&gt;
      &lt;TextView android:layout_width="fill_parent"
          android:layout_height="wrap_content" android:text="@string/hello" /&gt;
      &lt;RelativeLayout android:gravity="center"
          android:paddingTop="400dip" android:layout_width="fill_parent"
          android:layout_height="wrap_content"&gt;
          &lt;EditText android:background="@drawable/name_text_bg"
              android:layout_width="wrap_content" android:layout_height="wrap_content"
              android:gravity="center" /&gt;
      &lt;/RelativeLayout&gt;
  &lt;/RelativeLayout&gt;
  </code></pre>
  
  <p>When I run it on a 480x800 mdpi(160) simulator (scale to 7 inches), it works fine, but on a 480x800 hdpi simulator, it PADDING the EditText down to the near bottom of the screen, nearly 600px, is that 400dip x 240 / 160 ? And It seems has no difference with screen size even I scaled it to 4 inches. How to let padding work under different screen density? Thanks a lot!</p>