Fragmento de mapa V2 em um fragmento

Estou enfrentando algum problema "Null pointer Expcepttion no getmap ()" no Google Map Fragments. Eu quero inserir o mapfragment em um fragmento. Por favor, revise o código e deixe saber se estou usando a abordagem certa ou não. E deixe-me saber exatamente o que preciso fazer com o meu código para fazê-lo funcionar

Meu arquivo de layout:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent" 
  android:orientation="vertical"
  android:background="@drawable/bg2"
  android:weightSum="100">

<Button
    android:id="@+id/perx_button"
    android:layout_marginTop="70dip"
    android:layout_gravity="center"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:background="@drawable/perx_card_btn" />

<fragment
    android:id="@+id/map"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    class="com.google.android.gms.maps.SupportMapFragment" />

</LinearLayout>


public class PerxDetailedFragment extends SupportMapFragment {

  static final LatLng HAMBURG = new LatLng(53.558, 9.927);
  static final LatLng KIEL = new LatLng(53.551, 9.993);
 GoogleMap map;
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {

     FragmentTransaction ft = getFragmentManager().beginTransaction();

    map = ((SupportMapFragment) getFragmentManager().findFragmentById(R.id.map))
            .getMap();

    SupportMapFragment fmap = (SupportMapFragment) getFragmentManager().findFragmentById(R.id.map);

    if (fmap == null) {
        fmap = SupportMapFragment.newInstance();
        ft.add(R.id.map, fmap);
    }

    ft.commit();

    Marker hamburg = map.addMarker(new MarkerOptions().position(HAMBURG)
            .title("Hamburg"));
        Marker kiel = map.addMarker(new MarkerOptions()
            .position(KIEL)
            .title("Kiel")
            .snippet("Kiel is cool")
            .icon(BitmapDescriptorFactory
                .fromResource(R.drawable.ic_launcher)));

        // Move the camera instantly to hamburg with a zoom of 15.
        map.moveCamera(CameraUpdateFactory.newLatLngZoom(HAMBURG, 15));

        // Zoom in, animating the camera.
        map.animateCamera(CameraUpdateFactory.zoomTo(10), 2000, null);


     return inflater.inflate(R.layout.perx_detailed, null, false);
}
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);       


    }


}

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