title: SherlockFragment cannot be cast to Fragment, my activity is SherlockActivty
body: <p>I'm just getting started on learning fragments and this error is really frustrating me, I must be missing something simple:</p>
  
  <p>I get an error on launch saying that the Fragment class cannot be cast to android.app.Fragment - I'm not sure why</p>
  
  <p>xml for Activity:</p>
  
  <pre><code>&lt;RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:background="@color/background_blue" &gt;
  
      &lt;Button
          android:id="@+id/bStartTest"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:layout_alignParentBottom="true"
          android:layout_alignParentLeft="true"
          android:layout_marginBottom="16dp"
          android:layout_marginLeft="16dp"
          android:layout_marginRight="16dp"
          android:background="@drawable/btn_main"
          android:text="@string/start_test"
          android:textColor="@color/white"
          android:textSize="24sp" /&gt;
  
      &lt;ProgressBar
          android:id="@+id/pbGetDataBase"
          style="?android:attr/progressBarStyleLarge"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_centerHorizontal="true"
          android:layout_centerVertical="true"
          android:visibility="invisible" /&gt;
  
      &lt;TextView
          android:id="@+id/tvHomeTitle"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_alignParentLeft="true"
          android:layout_alignParentTop="true"
          android:padding="16dp"
          android:text="@string/app_name"
          android:textColor="@color/white"
          android:textSize="34sp" /&gt;
  
      &lt;LinearLayout
          android:id="@+id/firstTimeLayout"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:layout_alignParentLeft="true"
          android:layout_below="@+id/tvHomeTitle"
          android:background="@color/background_blue"
          android:orientation="vertical"
          android:paddingLeft="16dp"
          android:paddingRight="16dp"
           &gt;
  
          &lt;fragment
          android:id="@+id/overviewFragment"
          android:layout_width="match_parent"
          android:layout_height="fill_parent"
          class="com.mycqs.cardiology.OverviewFragment" /&gt;
  
      &lt;/LinearLayout&gt;
  
  &lt;/RelativeLayout&gt;
  </code></pre>
  
  <p>Activity class:</p>
  
  <pre><code>public class HomeActivity extends SherlockActivity {
  
  @Override
      protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_home);
      }
  }
  </code></pre>
  
  <p>Fragment class:</p>
  
  <pre><code>public class OverviewFragment extends SherlockFragment {
  
  
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
      View view = inflater.inflate(R.layout.temporary,
          container, false);
      return view;
    }
  
  }
  </code></pre>
  
  <p>--</p>
  
  <pre><code>06-28 22:27:48.077: E/AndroidRuntime(23806): FATAL EXCEPTION: main
  06-28 22:27:48.077: E/AndroidRuntime(23806): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mycqs.cardiology/com.mycqs.cardiology.HomeActivity}: android.view.InflateException: Binary XML file line #87: Error inflating class fragment
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2246)
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2296)
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at android.app.ActivityThread.access$700(ActivityThread.java:151)
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1281)
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at android.os.Handler.dispatchMessage(Handler.java:99)
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at android.os.Looper.loop(Looper.java:137)
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at android.app.ActivityThread.main(ActivityThread.java:5293)
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at java.lang.reflect.Method.invokeNative(Native Method)
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at java.lang.reflect.Method.invoke(Method.java:511)
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1102)
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869)
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at dalvik.system.NativeStart.main(Native Method)
  06-28 22:27:48.077: E/AndroidRuntime(23806): Caused by: android.view.InflateException: Binary XML file line #87: Error inflating class fragment
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:710)
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at android.view.LayoutInflater.rInflate(LayoutInflater.java:752)
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at android.view.LayoutInflater.rInflate(LayoutInflater.java:760)
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at android.view.LayoutInflater.inflate(LayoutInflater.java:495)
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at android.view.LayoutInflater.inflate(LayoutInflater.java:397)
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at android.view.LayoutInflater.inflate(LayoutInflater.java:353)
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:327)
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at com.actionbarsherlock.internal.ActionBarSherlockNative.setContentView(ActionBarSherlockNative.java:134)
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at com.actionbarsherlock.app.SherlockActivity.setContentView(SherlockActivity.java:229)
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at com.mycqs.cardiology.HomeActivity.onCreate(HomeActivity.java:58)
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at android.app.Activity.performCreate(Activity.java:5250)
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1097)
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2210)
  06-28 22:27:48.077: E/AndroidRuntime(23806):    ... 11 more
  06-28 22:27:48.077: E/AndroidRuntime(23806): Caused by: java.lang.ClassCastException: com.mycqs.cardiology.OverviewFragment cannot be cast to android.app.Fragment
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at android.app.Fragment.instantiate(Fragment.java:585)
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at android.app.Fragment.instantiate(Fragment.java:560)
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at android.app.Activity.onCreateView(Activity.java:4850)
  06-28 22:27:48.077: E/AndroidRuntime(23806):    at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:686)
  06-28 22:27:48.077: E/AndroidRuntime(23806):    ... 23 more
  </code></pre>