How to change fontFamily of TextView in Android

So I'd like to change the
android:fontFamily in Android but I don't see any pre-defined
fonts in Android. How do I select one of the pre-defined ones? I don't really need to
define my own TypeFace but all I need is something different from what it shows right
now.

            android:id="@+id/HeaderText"
 android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:layout_alignParentTop="true"

            android:layout_centerHorizontal="true"

            android:layout_marginTop="52dp"

            android:gravity="center"

 android:text="CallerBlocker"

            android:textSize="40dp"
 android:fontFamily="Arial"

            />

It seems what I
did up there won't really work! BTW android:fontFamily="Arial"
was a stupid attempt!