title: Set RelativeLayout child to fill unused space
body: <p>I have this layout:</p>
  
  <pre><code>&lt;RelativeLayout
      android:layout_width="match_parent"
      android:layout_height="match_parent" &gt;
  
      &lt;ImageView
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:src="@drawable/stat_brightness_off"
          android:layout_toLeftOf="@id/brightnessSeekBar" /&gt;
  
      &lt;SeekBar
          android:id="@+id/brightnessSeekBar"
          android:layout_width="wrap_content"
          android:layout_centerHorizontal="true"
          android:layout_height="wrap_content" /&gt;
  
      &lt;ImageView
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_toRightOf="@id/brightnessSeekBar"
          android:src="@drawable/stat_brightness_on" /&gt;
  &lt;/RelativeLayout&gt;
  </code></pre>
  
  <p>I need the <code>SeekBar</code> to fill all the horizontal space, unused by <code>ImageView</code>'s (they are about 64*64 px). What should I do?</p>