title: Set position / size of UI element as percentage of screen size
body: <p>I'm trying to work out if it's possible to use percentage positions/sizes when creating a layout. What I want is something like this...</p>
  
  <pre><code>^
  |
  |
  | 68%
  |
  |
  v
  Gallery (height equivalent of 16% total screen size)
  ^
  | 16%
  v
  </code></pre>
  
  <p>I'm testing on a device which in landscape has a display of 800x480 actual pixels and I'm currently forcing it with the following...</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:layout_width="fill_parent"
      android:layout_height="fill_parent" &gt; 
      &lt;Gallery 
          android:id="@+id/gallery"
          android:layout_width="fill_parent"
          android:layout_height="80px"
          android:layout_marginTop ="320px"
      /&gt;
  &lt;/RelativeLayout&gt;
  </code></pre>
  
  <p>Obviously I don't want to hard-code fixed <code>px</code> units but I can't use <code>68%</code> or <code>0.68</code> for <code>layout_marginTop</code> (for example). I've looked at <code>dp</code> units but I'm not sure if I can do it that way either.</p>
  
  <p>I have to admit UI design is a weak point of mine so any advice would be gratefully received.</p>
  
  <p><strong>EDIT:</strong> For future reference if anyone is looking for a similar answer, following Alan Moore's suggestion I have the following working exactly how I want it...</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:orientation="vertical"
      android:background="@drawable/bground"
      android:layout_width="fill_parent"
      android:layout_height="fill_parent" &gt;
      &lt;TextView
          android:layout_width="fill_parent"
          android:layout_height="0dp"
          android:layout_weight="0.68"
          android:background="@android:color/transparent"
      /&gt;
      &lt;Gallery 
          android:id="@+id/gallery"
          android:layout_width="fill_parent"
          android:layout_height="wrap_content"
          android:layout_weight="0.16"
      /&gt;
      &lt;TextView
          android:layout_width="fill_parent"
          android:layout_height="0dp"
          android:layout_weight="0.16" 
          android:background="@android:color/transparent"
      /&gt;
  &lt;/LinearLayout&gt;
  </code></pre>
  
  <p>I managed to find some other examples of using <code>layout_weight</code> and decided to set the <code>TextView</code> heights to <code>0dp</code> and also used floats for the weights. Working great. :)</p>