Android Studio CheckBox Proble

public class UserAdapter extends RecyclerView.Adapter<UserAdapter.ViewHolder> {

DoctorsModel list;


Context context;
Activity activity;
ChangeFragments changeFragments;

public UserAdapter(DoctorsModel list ,Context context, Activity activity)  {
    this.list = list;
    this.context = context;
    this.activity = activity;
    changeFragments = new ChangeFragments(context);
}

@NonNull
@Override
public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {

    View view = LayoutInflater.from(context).inflate(R.layout.usersitemlayout, parent, false);
    return new ViewHolder(view);
}

@Override
public void onBindViewHolder(@NonNull final ViewHolder holder, final int position) {

    holder.userName.setText(list.getDoctors().get(position).getFullName());
    Picasso.get().load(list.getDoctors().get(position).getImage().getUrl()).into(holder.userImage);



    holder.ChechKadin.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
        @Override
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
            if (holder.ChechKadin.isChecked()){
                Toast.makeText(context, "True", Toast.LENGTH_SHORT).show();

            }else {
                Toast.makeText(context, "False", Toast.LENGTH_SHORT).show();

            }
        }
    });

}


@Override
public int getItemCount() {
    return list.getDoctors().size();
}

public class ViewHolder extends RecyclerView.ViewHolder {
    TextView userName;
    CircleImageView userImage;
    CheckBox ChechKadin,ChechErkek;


    public ViewHolder(View itemView) {
        super(itemView);

        userName = itemView.findViewById(R.id.userName);
        userImage = itemView.findViewById(R.id.userImage);
        ChechKadin = itemView.findViewById(R.id.CheckKadin);
        ChechErkek = itemView.findViewById(R.id.CheckErkek);

    }
}

}

public class UsersFragment extends Fragment {

private View view;
private ChangeFragments changeFragments;

private RecyclerView kullaniciRecylerView;
private DoctorsModel list;
private UserAdapter userAdapter;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    view = inflater.inflate(R.layout.fragment_users, container, false);
    tanimla();
    getKullaniciler();
    return view;    }

public void tanimla()
{

    changeFragments = new ChangeFragments(getContext());
    kullaniciRecylerView = view.findViewById(R.id.userRecylerView);
    RecyclerView.LayoutManager layoutManager = new GridLayoutManager(getContext(),1);
    kullaniciRecylerView.setLayoutManager(layoutManager);
    list = new DoctorsModel();

}

public void getKullaniciler()
{
     Call<DoctorsModel> req = ManagerAll.getInstance().getUser();
    req.enqueue(new Callback<DoctorsModel>() {
        @Override
        public void onResponse(Call<DoctorsModel> call, Response<DoctorsModel> response) {

         //  list = (DoctorsModel) response.body().getDoctors();
             list = response.body();
            userAdapter = new UserAdapter(list,getContext(),getActivity());
            Log.i("kullaniciler",response.body().toString());
            kullaniciRecylerView.setAdapter(userAdapter);
        }
        @Override
        public void onFailure(Call<DoctorsModel> call, Throwable t) {

            Toast.makeText(getContext(), "HATAA:...!!", Toast.LENGTH_LONG).show();

        }
    });
}

}

Please share the class code (Activity or adapter) where you are using the check box. As per by the logs, it looks like initialization issue. If you are using inside the adapter class then inside View Holder

this.ChechKadin = (CheckBox) itemView.findViewById(R.id.ChechKadin); // Check if you have initialized the checkbox.

if you are using the check box inside the activity

ChechKadin =(CheckBox) findViewById(R.id.ChechKadin);