Android : textView.setText not working

I have a TextView in a fragment called "frontpage". In my MainActivity (also called frontpage, and the fragment is also there), I want to change the text of my textview. Here is my code in the Mainactivity:

public static class PlaceholderFragment extends Fragment {

public PlaceholderFragment() {


}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.fragment_frontpage, container, false);
    return rootView;

}
public void setText(String text){
    TextView textView = (TextView) getView().findViewById(R.id.NameView);
    textView.setText("HI!");
}

}

And here is my code in the xml layout for the textview:

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:id="@+id/NameView"
    android:layout_below="@+id/textView"
    android:layout_centerHorizontal="true" />

No errors are being shown, but when running the app, the textview stays empty. Why is that?