Endless Scroll RecyclerView

activity_main.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:layout_marginTop="10dp"
    android:orientation="vertical">
    <android.support.v4.widget.SwipeRefreshLayout
        android:id="@+id/swipeRefresh"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
        <android.support.v7.widget.RecyclerView
            android:id="@+id/rvList"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:scrollbars="vertical"/>
    </android.support.v4.widget.SwipeRefreshLayout>
</LinearLayout>

AdapterItem.java

import android.os.Handler;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ProgressBar;
import android.widget.TextView;

import com.esantiago.pagination.R;
import com.esantiago.pagination.entity.Item;

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

public class AdapterItem extends RecyclerView.Adapter<RecyclerView.ViewHolder>  {
    private final int VIEW_ITEM = 1;
    private final int VIEW_PROG = 0;

    private ArrayList<Item> itemList;

    private OnLoadMoreListener onLoadMoreListener;

    private boolean isMoreLoading = true;

    public interface OnLoadMoreListener{
        void onLoadMore();
    }

    public AdapterItem(OnLoadMoreListener onLoadMoreListener) {
        this.onLoadMoreListener=onLoadMoreListener;
        itemList =new ArrayList<>();
    }

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

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent,int viewType) {
        if (viewType == VIEW_ITEM) {
            return new StudentViewHolder(LayoutInflater.from(parent.getContext()).inflate(R.layout.item_text, parent, false));
        } else {
            return new ProgressViewHolder(LayoutInflater.from(parent.getContext()).inflate(R.layout.item_progress, parent, false));
        }
    }

    public void showLoading() {
        if (isMoreLoading && itemList != null && onLoadMoreListener != null) {
            isMoreLoading = false;
            new Handler().post(new Runnable() {
                @Override
                public void run() {
                    itemList.add(null);
                    notifyItemInserted(itemList.size() - 1);
                    onLoadMoreListener.onLoadMore();
                }
            });
        }
    }

    public void setMore(boolean isMore) {
        this.isMoreLoading = isMore;
    }

    public void dismissLoading() {
        if (itemList != null && itemList.size() > 0) {
            itemList.remove(itemList.size() - 1);
            notifyItemRemoved(itemList.size());
        }
    }

    public void addAll(List<Item> lst){
        itemList.clear();
        itemList.addAll(lst);
        notifyDataSetChanged();
    }

    public void addItemMore(List<Item> lst){
        int sizeInit = itemList.size();
        itemList.addAll(lst);
        notifyItemRangeChanged(sizeInit, itemList.size());
    }


    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        if (holder instanceof StudentViewHolder) {
            Item singleItem = (Item) itemList.get(position);
            ((StudentViewHolder) holder).tvItem.setText(singleItem.getItem());
        }
    }


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

    static class StudentViewHolder extends RecyclerView.ViewHolder {
        public TextView tvItem;

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

    static class ProgressViewHolder extends RecyclerView.ViewHolder {
        public ProgressBar pBar;
        public ProgressViewHolder(View v) {
            super(v);
            pBar = (ProgressBar) v.findViewById(R.id.pBar);
        }
    }
}

build.gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 26
    buildToolsVersion "26.0.2"

    defaultConfig {
        applicationId "com.esantiago.pagination"
        minSdkVersion 17
        targetSdkVersion 26
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:26.1.0'
    compile 'com.android.support:recyclerview-v7:26.1.0'
}

Item.java

import android.os.Parcel;
import android.os.Parcelable;

/**
 * Created by edwin on 19/03/16.
 */
public class Item  {

    private String item;

    public String getItem() {
        return item;
    }

    public void setItem(String item) {
        this.item = item;
    }


    public Item(String item) {
        this.item=item;
    }

}

item_progress.xml

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

    <ProgressBar
        android:id="@+id/pBar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:indeterminate="true"/>

</LinearLayout>

item_text.xml

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

    <TextView
        android:id="@+id/tvItem"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="30sp"/>

</LinearLayout>

MainActivity.java

import android.os.Handler;
import android.support.v4.widget.SwipeRefreshLayout;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.widget.TextView;

import com.esantiago.pagination.adapter.AdapterItem;
import com.esantiago.pagination.entity.Item;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity implements AdapterItem.OnLoadMoreListener
        , SwipeRefreshLayout.OnRefreshListener {


    private AdapterItem mAdapter;
    private ArrayList<Item> itemList;
    private SwipeRefreshLayout swipeRefresh;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        itemList = new ArrayList<>();
        swipeRefresh = findViewById(R.id.swipeRefresh);
        RecyclerView mRecyclerView = findViewById(R.id.rvList);
        LinearLayoutManager mLayoutManager = new LinearLayoutManager(this);
        mRecyclerView.setLayoutManager(mLayoutManager);
        mAdapter = new AdapterItem(this);
        mRecyclerView.setAdapter(mAdapter);
        swipeRefresh.setOnRefreshListener(this);
        mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
                super.onScrolled(recyclerView, dx, dy);
                LinearLayoutManager llManager = (LinearLayoutManager) recyclerView.getLayoutManager();
                if (dy > 0 && llManager.findLastCompletelyVisibleItemPosition() == (mAdapter.getItemCount() - 2)) {
                    mAdapter.showLoading();
                }
            }
        });


    }

    @Override
    protected void onStart() {
        super.onStart();
        Log.d("MainActivity_", "onStart");
        loadData();
    }

    @Override
    public void onRefresh() {
        Log.d("MainActivity_", "onRefresh");
        new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {
                swipeRefresh.setRefreshing(false);
                loadData();

            }
        }, 2000);
    }

    @Override
    public void onLoadMore() {
        Log.d("MainActivity_", "onLoadMore");
        new AsyncTask<Void, Void, List<Item>>() {
            @Override
            protected List<Item> doInBackground(Void... voids) {
                /**
                 *    Delete everything what is below // and place your code logic
                 */
                ///////////////////////////////////////////
                int start = mAdapter.getItemCount() - 1;
                int end = start + 15;
                List<Item> list = new ArrayList<>();
                if (end < 200) {
                    for (int i = start + 1; i <= end; i++) {
                        list.add(new Item("Item " + i));
                    }
                }
                try {
                    Thread.sleep(1500);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                /////////////////////////////////////////////////
                return list;

            }

            @Override
            protected void onPostExecute(List<Item> items) {
                super.onPostExecute(items);
                mAdapter.dismissLoading();
                mAdapter.addItemMore(items);
                mAdapter.setMore(true);
            }
        }.execute();

    }

    private void loadData() {
        itemList.clear();
        for (int i = 1; i <= 20; i++) {
            itemList.add(new Item("Item " + i));
        }
        mAdapter.addAll(itemList);
    }

}

Please, can you show a similar example where the data source will be JSON? I can seem to implement this because I am using json.

Please, can you show a similar example where the data source will be JSON? I can seem to implement this because I am using json.