title: Cannot call getSupportFragmentManager() from activity
body: <p>I have an activity which has a fragment.</p>
  
  <p>XML:</p>
  
  <pre><code> &lt;fragment android:name="com.example.androidcalculator.ResultFragment"
              android:id="@+id/result_fragment"
              android:layout_weight="1"
              android:layout_width="match_parent"
              android:layout_height="wrap_content" /&gt;
  </code></pre>
  
  <p>And I want to call a method from ResultFragment from a method in the Activity, but getSupportFragmentManager "doesn't exist":</p>
  
  <pre><code>FragmentManager fragMan = getSupportFragmentManager();
  </code></pre>
  
  <p>How can I resolve this?</p>