title: findViewById returns null for preference layout
body: <p>I have a preference screen (responder_generic.xml) as follows:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android" &gt;
  
      &lt;Preference
          android:defaultValue="false"
          android:key="auto_responder_key"
          android:layout="@layout/preference_header_switch_item_responder"
          android:title="@string/auto_responder"&gt;
      &lt;/Preference&gt;
  
  &lt;/PreferenceScreen&gt;
  </code></pre>
  
  <p>which i am instantiating as follows : (in version 2.3.3)</p>
  
  <pre><code>addPreferencesFromResource(R.xml.responder_generic);
  </code></pre>
  
  <p>and my layout = <code>preference_header_switch_item_responder</code> looks as follows:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;!-- Layout of a header item in PreferenceActivity. --&gt;
  &lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:layout_width="match_parent"
      android:layout_height="33dp"
      android:gravity="center_vertical"
      android:minHeight="33dp"
      android:id="@+id/preference_header_switch_item_responder"
      style="?android:attr/listSeparatorTextViewStyle" &gt;
  
      &lt;RelativeLayout
          android:layout_width="0dip"
          android:layout_height="wrap_content"
          android:layout_marginLeft="5dp"
          android:layout_weight="1" &gt;
  
          &lt;TextView
              android:id="@+id/title"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              android:ellipsize="marquee"
              android:fadingEdge="horizontal"
              android:singleLine="true"
              android:text="@string/auto_responder"
              android:textAppearance="?android:attr/textAppearanceSmall"
              android:textStyle="bold" /&gt;
  
          &lt;TextView
              android:id="@+id/summary"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              android:layout_below="@android:id/title"
              android:ellipsize="end"
              android:textAppearance="?android:attr/textAppearanceSmall" /&gt;
      &lt;/RelativeLayout&gt;
  
      &lt;include layout="@layout/compound_button" /&gt;
  
  &lt;/LinearLayout&gt;
  </code></pre>
  
  <p>Now, i have the compound button defined in <code>layout</code> folder and <code>layout/v-14</code> respectively as follows :</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;merge xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" &gt;
  
  &lt;CheckBox
      android:id="@+id/switchWidget"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_gravity="center"
      android:clickable="true"
      android:focusable="false"
      android:padding="8dip"
      android:layout_marginRight="14dip" /&gt;
  
  &lt;/merge&gt;
  </code></pre>
  
  <p>and</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;merge xmlns:android="http://schemas.android.com/apk/res/android"
      android:layout_width="match_parent"
      android:layout_height="match_parent" &gt;
  
      &lt;Switch
          android:id="@+id/switchWidget"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_gravity="center"
          android:clickable="true"
          android:focusable="false"
          android:padding="8dip" 
          android:layout_marginRight="14dip"/&gt;
  
  &lt;/merge&gt;
  </code></pre>
  
  <p>In the <code>onPostCreate</code> method, i am trying to find the this checkbox/switch at run time using <code>findViewById(R.id.switchWidget)</code> but its always returning null. </p>
  
  <p>Any idea what could be the reason ?</p>