Pagination in RecyclerView

Introduction

Pagination is a common issue with for a lot of mobile apps that need to deal with lists of data. Most of the mobile apps are now starting to take up the "endless page" model, where scrolling automatically loads in new content. CWAC Endless Adapter makes it really easy to use this pattern in Android applications

MainActivity.java

import android.os.Bundle;
import android.os.Handler;
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.util.Log;
import android.widget.TextView;

import com.android.volley.Request;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.VolleyLog;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class MainActivity extends AppCompatActivity {

    private static final String TAG = "MainActivity";
    private Toolbar toolbar;

    private TextView tvEmptyView;
    private RecyclerView mRecyclerView;
    private DataAdapter mAdapter;
    private LinearLayoutManager mLayoutManager;
    private int mStart=0,mEnd=20;
    private List<Student> studentList;
    private List<Student> mTempCheck;
    public static int pageNumber;
    public int total_size=0;


    protected Handler handler;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        pageNumber = 1;
        toolbar = (Toolbar) findViewById(R.id.toolbar);
        tvEmptyView = (TextView) findViewById(R.id.empty_view);
        mRecyclerView = (RecyclerView) findViewById(R.id.my_recycler_view);
        studentList = new ArrayList<>();
        mTempCheck=new ArrayList<>();
        handler = new Handler();
        if (toolbar != null) {
            setSupportActionBar(toolbar);
            getSupportActionBar().setTitle("Android Students");

        }

        mRecyclerView.setHasFixedSize(true);
        mLayoutManager = new LinearLayoutManager(this);
        mRecyclerView.setLayoutManager(mLayoutManager);
        mAdapter = new DataAdapter(studentList, mRecyclerView);
        mRecyclerView.setAdapter(mAdapter);
        GetGroupData("" + mStart, "" + mEnd);
        mAdapter.setOnLoadMoreListener(new OnLoadMoreListener() {
            @Override
            public void onLoadMore() {
                if( mTempCheck.size()> 0) {
                    studentList.add(null);
                    mAdapter.notifyItemInserted(studentList.size() - 1);
                    int start = pageNumber * 20;
                    start = start + 1;
                    ++ pageNumber;
                    mTempCheck.clear();
                    GetData("" + start,""+ mEnd);
                }
            }
        });
    }

    public void GetData(final String LimitStart, final String LimitEnd) {
        Map<String, String> params = new HashMap<>();
        params.put("LimitStart", LimitStart);
        params.put("Limit", LimitEnd);
        Custom_Volly_Request jsonObjReq = new Custom_Volly_Request(Request.Method.POST,
                "Your php file link", params,
                new Response.Listener<JSONObject>() {
                    @Override
                    public void onResponse(JSONObject response) {
                        Log.d("ResponseSuccess",response.toString());
                        // handle the data from the servoce
                    }
                }, new Response.ErrorListener() {

            @Override
            public void onErrorResponse(VolleyError error) {
                VolleyLog.d("ResponseErrorVolly: " + error.getMessage());

            }});
       
    }
    // load initial data
    private void loadData(int start,int end,boolean notifyadapter) {
        for (int i = start; i <= end; i++) {
            studentList.add(new Student("Student " + i, "androidstudent" + i + "@gmail.com"));
            if(notifyadapter)
                mAdapter.notifyItemInserted(studentList.size());
        }
    }
}

OnLoadMoreListener.java

public interface OnLoadMoreListener { void onLoadMore(); }

DataAdapter.java

import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;

import java.util.List;

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)) {
                                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.progress_item, parent, false);
            vh = new ProgressViewHolder(v);
        }
        return vh;
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        if (holder instanceof StudentViewHolder) {
            Student singleStudent=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(boolean state) {
        loading = state;
    }

    @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);

            
        }
    }

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

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

}
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