FirestoreRecyclerAdapter not fetching data and returning model class variable as null

Question

I am trying to fetch a students data from Firestore Collection and then display it in Recycler view My Firestore Collection and Document : Collection Name is School Code, Document contains Student Info

Model Class :(Student_Model_Class)

package com.example.firestooredemo;

import java.sql.Timestamp;
import java.util.HashMap;

public class sdm {
    private HashMap<String, String> QnA;
    private String formname;
    private String schoolid;
    private String standard;
    private String studentname;
    private String subject;
    private Timestamp timestamp;

    private sdm(){}

    private sdm(HashMap qna,String formname,String schoolid,String standard,String studentname,String subject,Timestamp timestamp){
        this.QnA=qna;
        this.formname=formname;
        this.schoolid=schoolid;
        this.standard=standard;
        this.studentname=studentname;
        this.subject=subject;
        this.timestamp=timestamp;
    }

    public HashMap<String, String> getQnA() {
        return QnA;
    }

    public void setQnA(HashMap<String, String> qnA) {
        QnA = qnA;
    }

    public String getFormname() {
        return formname;
    }

    public void setFormname(String formname) {
        this.formname = formname;
    }

    public String getSchoolid() {
        return schoolid;
    }

    public void setSchoolid(String schoolid) {
        this.schoolid = schoolid;
    }

    public String getStandard() {
        return standard;
    }

    public void setStandard(String standard) {
        this.standard = standard;
    }

    public String getStudentname() {
        return studentname;
    }

    public void setStudentname(String studentname) {
        this.studentname = studentname;
    }

    public String getSubject() {
        return subject;
    }

    public void setSubject(String subject) {
        this.subject = subject;
    }

    public String getTimestamp() {
        return timestamp.toString();
    }

    public void setTimestamp(Timestamp timestamp) {
        this.timestamp = timestamp;
    }
}

Activity.java :

package com.example.firestooredemo;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.*;

import com.firebase.ui.firestore.FirestoreRecyclerAdapter;
import com.firebase.ui.firestore.FirestoreRecyclerOptions;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.firestore.FirebaseFirestore;
import com.google.firebase.firestore.Query;
import com.google.firebase.firestore.QueryDocumentSnapshot;
import com.google.firebase.firestore.QuerySnapshot;

import java.util.List;

public class DisplayRecord extends AppCompatActivity {
    TextView Record_Title,DemoD;
    private FirebaseFirestore Fs;
    private RecyclerView FSList;
    private FirestoreRecyclerAdapter<sdm,Student_View_Holder> F_Adapter;
    String S_ID,Student;
    List<sdm> stud;
    int S_id;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_display_record);
        FSList=(RecyclerView) findViewById(R.id.RCView);
        FSList.setHasFixedSize(true);
        FSList.setLayoutManager(new LinearLayoutManager(this));
        Intent intent = getIntent();
        Fs=FirebaseFirestore.getInstance();
        Record_Title= (TextView) findViewById(R.id.RecordTitle);
        S_ID = intent.getStringExtra("School ID");
        Record_Title.setText("Records of "+S_ID);
        Log.d("Datacheck","School :"+S_ID);
        S_id=Integer.parseInt(S_ID);
        String TAG="Datacheck";

        Fs.collection("EM_DEMO2").document("10th_STD").collection(S_ID)
                .whereEqualTo("formname","Tourism, Transport and Communication3")
                .get()
                .addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
                    @Override
                    public void onComplete(@NonNull Task<QuerySnapshot> task) {
                        if (task.isSuccessful()) {
                            for (QueryDocumentSnapshot document : task.getResult()) {
                                Log.d(TAG, document.getId() + " => " + document.getData().toString());
                                Student=Student+document.getLong("standard")+"\n"+document.get("subject")+"\n"+document.get("formname")+"\n-----\n";
//                                stud.add(document.toObject(s1));
                                Log.d("IMOP",Student);
                            }
                        } else {
                            Log.d(TAG, "Error getting documents: ", task.getException());
                        }
                    }
                });
        //Query Part
        Query Q=Fs.collection("EM_DEMO2").document("10th_STD").collection(S_ID).whereEqualTo("formname","Tourism, Transport and Communication3");

        // Recycler view Display
        FirestoreRecyclerOptions<sdm> Opt=new FirestoreRecyclerOptions.Builder<sdm>()
                .setQuery(Q,sdm.class)
                .build();

        F_Adapter = new FirestoreRecyclerAdapter<sdm, Student_View_Holder>(Opt) {
            @NonNull
            @Override
            public Student_View_Holder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
                View V= LayoutInflater.from(parent.getContext()).inflate(R.layout.student_data,parent,false);
                return new Student_View_Holder(V);
            }

            @Override
            protected void onBindViewHolder(@NonNull Student_View_Holder holder, int position, @NonNull sdm model) {
                holder.StudentName.setText(model.getStudentname());
                holder.Standard.setText(model.getStandard());
                holder.SchoolID.setText(model.getSchoolid()+"");
                holder.Subject.setText(model.getSubject());
                holder.FormName.setText(model.getFormname());
//                holder.Time.setText(model.getTs()+"");
            }
        };


        FSList.setAdapter(F_Adapter);

        //View Holder
    }

    private class Student_View_Holder extends RecyclerView.ViewHolder {
        private TextView StudentName,Standard,Subject,SchoolID,FormName,Time;
        public Student_View_Holder(@NonNull View itemView) {
            super(itemView);
            StudentName = itemView.findViewById(R.id.StudentName);
            Standard = itemView.findViewById(R.id.Std);
            Subject = itemView.findViewById(R.id.Sub);
            SchoolID = itemView.findViewById(R.id.SchoolID);
            FormName = itemView.findViewById(R.id.FormName);
            Time = itemView.findViewById(R.id.Timestamp);
        }
    }

    @Override
    protected void onStart() {
        super.onStart();
        F_Adapter.startListening();
    }

    @Override
    protected void onStop() {
        super.onStop();
        if(F_Adapter!= null){
            F_Adapter.stopListening();
        }
    }
}

Student_data design : XML Design Screenshot But In app Recycler view only display fetched values of Subject,

App Output

I put some log messages in Student Data Model Class,to check if data is being fetched or not. But those logs doesn't even show up Log Messages :

Logs with Tag : Datacheck
Log with Tag : IMOP

Kindly please help with this,
thanks in advance.