Android relative layout problem with gravity

How can i put textview with id="naslov" to the center? I also tried with layout_gravity="center" but that doesn't work either.

android:layout_width="fill_parent"
android:layout_height="fill_parent">

    android:id="@+id/naslov"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textSize="20dip"
    android:text="Povzetek"
    android:gravity="center"/>

       android:id="@+id/aha"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textSize="10dip"
    android:text="Vseh oddaj:"
       android:layout_below="@id/naslov"/>  
  

Answer

 android:layout_centerHorizontal="true"