Não estou conseguindo recuperar o id em um fragment JAVA

Quando vou executar o App ele Fecha!

package com.example.myapplication.Fragments;
import android.os.Bundle;
import androidx.fragment.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageButton;
import com.example.myapplication.R;

/**

  • A simple {@link Fragment} subclass.
    */
    public class CaoFragment extends Fragment {private ImageButton buttonCao;public CaoFragment() {}
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
    Bundle savedInstanceState) {
 View view = inflater.inflate(R.layout.fragment_cao, container, false);
 buttonCao = view.findViewById(R.id.buttonCao);
 return view;

}
}

Erro
at com.example.myapplication.Fragments.CaoFragment.onCreateView(CaoFragment.java:30)