LoadMore RecyclerView with progress bar showing at bottom

I am trying to get Endless Recycler View with progress bar showing at bottom when you are loading data from web service. But faced different problems.
Finally found a solution at this link. May be someone needs this.

build.gradle

---------------------

compile 'com.android.support:recyclerview-v7:24.0.0'
compile 'com.android.support:cardview-v7:24.0.0'

activity_main.xml

---------------------------

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="sgp.anil.com.firebaseexample.MainActivity"
    tools:showIn="@layout/activity_main">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/my_recycler_view"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:scrollbars="vertical" />

    <TextView
        android:id="@+id/empty_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center"
        android:text="No Records"
        android:visibility="gone" />
</LinearLayout>

 list_row.xml

-----------------------

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:card_view="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    card_view:cardCornerRadius="5dp"
    card_view:cardUseCompatPadding="true">

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="?android:selectableItemBackground">

        <TextView
            android:id="@+id/tvName"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_margin="5dp"
            android:text="Name"
            android:textColor="@android:color/black"
            android:textSize="18sp" />

        <TextView
            android:id="@+id/tvEmailId"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_below="@+id/tvName"
            android:layout_margin="5dp"
            android:text="Email Id"
            android:textColor="@android:color/black"
            android:textSize="12sp" />
    </RelativeLayout>

</android.support.v7.widget.CardView>

 progressbar.xml

-------------------------

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <ProgressBar
        android:id="@+id/progressBar1"
        android:layout_width="wrap_content"
        android:layout_gravity="center_horizontal"
        android:layout_height="wrap_content" />

</LinearLayout>

 Student.Java

-------------------------

package sgp.anil.com.loadmore.utils;

import java.io.Serializable;

/**
 * Created by Anil on 05-08-2016.
 */
public class Student implements Serializable {

    private static final long serialVersionUID = 1L;

    private String name;

    private String emailId;

    public Student() {

    }

    public Student(String name, String emailId) {
        this.name = name;
        this.emailId = emailId;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getEmailId() {
        return emailId;
    }

    public void setEmailId(String emailId) {
        this.emailId = emailId;
    }
}

 OnLoadMoreListener.Java

--------------------------------

package sgp.anil.com.loadmore.utils;

/**
 * Created by Anil on 05-08-2016.
*/

public interface OnLoadMoreListener {

    void onLoadMore();
}

DataAdapter.Java

-------------------------

package sgp.anil.com.loadmore.adapters;

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 android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;

import java.util.List;

import sgp.anil.com.loadmore.R;
import sgp.anil.com.loadmore.utils.OnLoadMoreListener;
import sgp.anil.com.loadmore.utils.Student;

/**
 * Created by Anil on 05-08-2016.
 */
public class DataAdapter extends RecyclerView.Adapter {
    private final int VIEW_ITEM = 1;
    private final int VIEW_PROG = 0;

    private List<Student> studentList;

    // The minimum amount of items to have below your current scroll position
    // before loading more.
    private int visibleThreshold = 5;
    private int lastVisibleItem, totalItemCount;
    private boolean loading;
    private OnLoadMoreListener onLoadMoreListener;


    public DataAdapter(List<Student> students, RecyclerView recyclerView) {
        studentList = students;

        if (recyclerView.getLayoutManager() instanceof LinearLayoutManager) {

            final LinearLayoutManager linearLayoutManager = (LinearLayoutManager) recyclerView
                    .getLayoutManager();


            recyclerView
                    .addOnScrollListener(new RecyclerView.OnScrollListener() {
                        @Override
                        public void onScrolled(RecyclerView recyclerView,
                                               int dx, int dy) {
                            super.onScrolled(recyclerView, dx, dy);

                            totalItemCount = linearLayoutManager.getItemCount();
                            lastVisibleItem = linearLayoutManager
                                    .findLastVisibleItemPosition();
                            if (!loading
                                    && totalItemCount <= (lastVisibleItem + visibleThreshold)) {
                                // End has been reached
                                // Do something
                                if (onLoadMoreListener != null) {
                                    onLoadMoreListener.onLoadMore();
                                }
                                loading = true;
                            }
                        }
                    });
        }
    }

    @Override
    public int getItemViewType(int position) {
        return studentList.get(position) != null ? VIEW_ITEM : VIEW_PROG;
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent,
                                                      int viewType) {
        RecyclerView.ViewHolder vh;
        if (viewType == VIEW_ITEM) {
            View v = LayoutInflater.from(parent.getContext()).inflate(
                    R.layout.list_row, parent, false);

            vh = new StudentViewHolder(v);
        } else {
            View v = LayoutInflater.from(parent.getContext()).inflate(
                    R.layout.progressbar_item, parent, false);

            vh = new ProgressViewHolder(v);
        }
        return vh;
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        if (holder instanceof StudentViewHolder) {

            Student singleStudent = (Student) studentList.get(position);

            ((StudentViewHolder) holder).tvName.setText(singleStudent.getName());

            ((StudentViewHolder) holder).tvEmailId.setText(singleStudent.getEmailId());

            ((StudentViewHolder) holder).student = singleStudent;

        } else {
            ((ProgressViewHolder) holder).progressBar.setIndeterminate(true);
        }
    }

    public void setLoaded() {
        loading = false;
    }

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

    public void setOnLoadMoreListener(OnLoadMoreListener onLoadMoreListener) {
        this.onLoadMoreListener = onLoadMoreListener;
    }


    //
    public static class StudentViewHolder extends RecyclerView.ViewHolder {
        public TextView tvName;

        public TextView tvEmailId;

        public Student student;

        public StudentViewHolder(View v) {
            super(v);
            tvName = (TextView) v.findViewById(R.id.tvName);

            tvEmailId = (TextView) v.findViewById(R.id.tvEmailId);

            v.setOnClickListener(new View.OnClickListener() {

                @Override
                public void onClick(View v) {
                    Toast.makeText(v.getContext(),
                            "OnClick :" + student.getName() + " \n " + student.getEmailId(),
                            Toast.LENGTH_SHORT).show();

                }
            });
        }
    }

    public static class ProgressViewHolder extends RecyclerView.ViewHolder {
        public ProgressBar progressBar;

        public ProgressViewHolder(View v) {
            super(v);
            progressBar = (ProgressBar) v.findViewById(R.id.progressBar1);
        }
    }
}

 MainActivity.Java

--------------------------

package sgp.anil.com.loadmore;

import android.os.Bundle;
import android.os.Handler;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.widget.TextView;

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

import sgp.anil.com.firebaseexample.adapters.DataAdapter;
import sgp.anil.com.firebaseexample.utils.OnLoadMoreListener;
import sgp.anil.com.firebaseexample.utils.Student;

public class MainActivity extends AppCompatActivity {

    private TextView tvEmptyView;
    private RecyclerView mRecyclerView;
    private DataAdapter mAdapter;
    private LinearLayoutManager mLayoutManager;

    private List<Student> studentList;
   
    protected Handler handler;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
      tvEmptyView = (TextView) findViewById(R.id.empty_view);
        mRecyclerView = (RecyclerView) findViewById(R.id.my_recycler_view);
        studentList = new ArrayList<Student>();
        handler = new Handler();
        if (toolbar != null) {
            setSupportActionBar(toolbar);
            getSupportActionBar().setTitle("SGP Students");

        }
        loadData();

        // use this setting to improve performance if you know that changes
        // in content do not change the layout size of the RecyclerView
        mRecyclerView.setHasFixedSize(true);

        mLayoutManager = new LinearLayoutManager(this);

        // use a linear layout manager
        mRecyclerView.setLayoutManager(mLayoutManager);

        // create an Object for Adapter
        mAdapter = new DataAdapter(studentList, mRecyclerView);

        // set the adapter object to the Recyclerview
        mRecyclerView.setAdapter(mAdapter);
        //  mAdapter.notifyDataSetChanged();


        if (studentList.isEmpty()) {
            mRecyclerView.setVisibility(View.GONE);
            tvEmptyView.setVisibility(View.VISIBLE);

        } else {
            mRecyclerView.setVisibility(View.VISIBLE);
            tvEmptyView.setVisibility(View.GONE);
        }

        mAdapter.setOnLoadMoreListener(new OnLoadMoreListener() {
            @Override
            public void onLoadMore() {
                //add null , so the adapter will check view_type and show progress bar at bottom
                studentList.add(null);
                mAdapter.notifyItemInserted(studentList.size() - 1);

                handler.postDelayed(new Runnable() {
                    @Override
                    public void run() {
                        //   remove progress item
                        studentList.remove(studentList.size() - 1);
                        mAdapter.notifyItemRemoved(studentList.size());
                        //add items one by one
                        int start = studentList.size();
                        int end = start + 20;

                        for (int i = start + 1; i <= end; i++) {
                            studentList.add(new Student("Student " + i, "AndroidStudent" + i + "@gmail.com"));
                            mAdapter.notifyItemInserted(studentList.size());
                        }
                        mAdapter.setLoaded();
                        //or you can add all at once but do not forget to call mAdapter.notifyDataSetChanged();
                    }
                }, 2000);

            }
        });

    }


    // load initial data
    private void loadData() {

        for (int i = 1; i <= 20; i++) {
            studentList.add(new Student("Student " + i, "androidstudent" + i + "@gmail.com"));

        }


    }

}