Expandable Recyclerview findViewById(int) cannot be resolved

error findViewById(int) cannot resolve method

trying to achieve in fragment

A custom RecyclerView which allows for an expandable view to be attached to each ViewHolder

Is there a way i could click operation in expanded view

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.bignerdranch.expandablerecyclerview.Model.ParentObject;
import com.blipclap.engineering_solution.Adapter.adapter;
import com.blipclap.engineering_solution.Models.TitleChild;
import com.blipclap.engineering_solution.Models.TitleCreator;
import com.blipclap.engineering_solution.Models.TitleParent;

import java.util.ArrayList;
import java.util.List;


public class SYFragment extends Fragment {
    RecyclerView recyclerView;

    @Override
    public void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        ((adapter)recyclerView.getAdapter()).onSaveInstanceState(outState);
    }

    @Override
    public void onCreate( Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        recyclerView =(RecyclerView)findViewById(R.id.recyclerview);
        recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));

        adapter adapter =new adapter(getActivity(),initData());
        adapter.setParentClickableViewAnimationDefaultDuration();
        adapter.setParentAndIconExpandOnClick(true);

        recyclerView.setAdapter(adapter);
    }

    private List<ParentObject> initData() {
        TitleCreator titleCreator =TitleCreator.get(getActivity());
        List<TitleParent> titles = titleCreator.getall();
        List<ParentObject> parentObjects =new ArrayList<>();
        for (TitleParent title:titles)
        {
            List<Object> childList =new ArrayList<>();
            childList.add((new TitleChild("Add to contact","send message")));
            title.setChildObjectList(childList);
            parentObjects.add(title);
        }
        return parentObjects;
    }

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        //returning our layout file
        //change R.layout.yourlayoutfilename for each of your fragments
        return inflater.inflate(R.layout.fragment_sy, container, false);
    }


    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        //you can set the title for your toolbar here for different fragments different titles
        getActivity().setTitle("Syllabus");
    }
}

Trying to achieve Expandable Recyclerview

Error:(34, 37) error: cannot find symbol method findViewById(int)

findViewById is not a Fragment method so it cannot be resolved in its onCreate. You cannot do like in an Activity.

You have to use it in your onCreateView or onViewCreated methods, and you have to call it on the view you inflated.

For example:

@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    //you can set the title for your toolbar here for different fragments different titles
    getActivity().setTitle("Syllabus");

    recyclerView =(RecyclerView) view.findViewById(R.id.recyclerview);
    recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));

    adapter adapter =new adapter(getActivity(),initData());
    adapter.setParentClickableViewAnimationDefaultDuration();
    adapter.setParentAndIconExpandOnClick(true);

    recyclerView.setAdapter(adapter)
}

Or..

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    //returning our layout file
    //change R.layout.yourlayoutfilename for each of your fragments
    View rootView = inflater.inflate(R.layout.fragment_sy, container, false);

    recyclerView =(RecyclerView) rootView.findViewById(R.id.recyclerview);

     ...
    return rootView;
}