Android ช่วยหน่อยค่ะ ไม่สามารถ Set textview ได้ เกิด Error java.lang.nullpointerexception

public class Fragment1 extends Fragment {

    String data;
   // public static final String KEY_USERNAME1="User_Username";
    public Fragment1() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        View rootView=inflater.inflate(R.layout.fragment, container, false);
        TextView get = (TextView)getActivity().findViewById(R.id.textView25);

        Bundle bundle=getArguments();
        if (bundle!=null){
        data=bundle.getString("KEY");
        }
        Toast.makeText(getActivity(), data, Toast.LENGTH_SHORT).show();
        get.setText(data);
        return rootView;

    }
}