title: How to remove a preference from PreferenceActivity?
body: <p>I'm using PreferenceActivity. How do I remove a preference? I cannot seem to get this to work:</p>
  
  <pre><code>Preference p = findPreference("grok");
  boolean worked = getPreferenceScreen().removePreference(p);
  // worked == false.
  </code></pre>
  
  <p>So the preference is found, but the removePreference() call fails. What's the right way to do this? I'm using a preference.xml file for the keys like so:</p>
  
  <pre><code>&lt;PreferenceScreen
      xmlns:android="http://schemas.android.com/apk/res/android"&gt;
  
      &lt;PreferenceCategory
          android:title="foo"&gt;
  
          &lt;CheckBoxPreference
              android:key="grok" /&gt;
  
              ...
  </code></pre>
  
  <p>Thanks</p>