How to Upload Excel/Google Sheet Data to Firebase Realtime Database in Android?

package org.geeksforgeeks.demo;

public class UserModal {
  
    // variables for our first name, 
    // last name, email and avatar
    private String first_name;
    private String last_name;
    private String email;
    private String avatar;

    public String getFirst_name() {
        return first_name;
    }

    public void setFirst_name(String first_name) {
        this.first_name = first_name;
    }

    public String getLast_name() {
        return last_name;
    }

    public void setLast_name(String last_name) {
        this.last_name = last_name;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getAvatar() {
        return avatar;
    }

    public void setAvatar(String avatar) {
        this.avatar = avatar;
    }

    public UserModal(String first_name, String last_name, String email, String avatar) {
        this.first_name = first_name;
        this.last_name = last_name;
        this.email = email;
        this.avatar = avatar;
    }
}

package org.geeksforgeeks.demo;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

import com.squareup.picasso.Picasso;

import java.util.ArrayList;

public class UserRVAdapter extends RecyclerView.Adapter<UserRVAdapter.ViewHolder> {
  
    // variable for our array list and context.
    private ArrayList<UserModal> userModalArrayList;
    private Context context;

    // creating a constructor.
    public UserRVAdapter(ArrayList<UserModal> userModalArrayList, Context context) {
        this.userModalArrayList = userModalArrayList;
        this.context = context;
    }

    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        // inflating our layout file on below line.
        View view = LayoutInflater.from(context).inflate(R.layout.user_rv_item, parent, false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
      
        // getting data from our array list in our modal class.
        UserModal userModal = userModalArrayList.get(position);
        
          // on the below line we are setting data to our text view.
        holder.firstNameTV.setText(userModal.getFirst_name());
        holder.lastNameTV.setText(userModal.getLast_name());
        holder.emailTV.setText(userModal.getEmail());
      
        // on below line we are loading our image from the URL 
        // in our image view using Picasso.
        Picasso.get().load(userModal.getAvatar()).into(holder.userIV);
    }

    @Override
    public int getItemCount() {
        // returning the size of array list.
        return userModalArrayList.size();
    }

    public class ViewHolder extends RecyclerView.ViewHolder {
      
        // creating a variable for our text view and image view.
        private TextView firstNameTV, lastNameTV, emailTV;
        private ImageView userIV;

        public ViewHolder(@NonNull View itemView) {
            super(itemView);
          
            // initializing our variables.
            firstNameTV = itemView.findViewById(R.id.idTVFirstName);
            lastNameTV = itemView.findViewById(R.id.idTVLastName);
            emailTV = itemView.findViewById(R.id.idTVEmail);
            userIV = itemView.findViewById(R.id.idIVUser);
        }
    }
}

package org.geeksforgeeks.demo;

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

public final class SheetRow {
    private final List<String> cells;

    public SheetRow(List<String> cells) {
        this.cells = cells;
    }

    public List<String> getCells() {
        return cells;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        SheetRow sheetRow = (SheetRow) o;
        return Objects.equals(cells, sheetRow.cells);
    }

    @Override
    public int hashCode() {
        return Objects.hash(cells);
    }

    @Override
    public String toString() {
        return "SheetRow{" +
                "cells=" + cells +
                '}';
    }
}

package org.geeksforgeeks.demo;

import android.os.AsyncTask;
import android.os.Bundle;
import android.widget.Button;
import android.widget.Toast;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import com.google.firebase.FirebaseApp;
import com.google.firebase.database.FirebaseDatabase;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    private Button fetchButton, uploadButton;
    private RecyclerView sheetRecyclerView;
    private UserRVAdapter userRVAdapter;
    private ArrayList<UserModal> userModalArrayList = new ArrayList<>();

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

        FirebaseApp.initializeApp(this);

        fetchButton = findViewById(R.id.fetchButton);
        uploadButton = findViewById(R.id.uploadButton);
        sheetRecyclerView = findViewById(R.id.sheetRecyclerView);

        userRVAdapter = new UserRVAdapter(userModalArrayList, this);
        sheetRecyclerView.setLayoutManager(new LinearLayoutManager(this));
        sheetRecyclerView.setAdapter(userRVAdapter);

        fetchButton.setOnClickListener(v -> {
            String url = "https://docs.google.com/spreadsheets/d/e/2PACX-1vQlLsJUKrUv22ulAXvBXLwT2rcMhSOKOS4BiIAPc-WZQTssJ5S0LeIWDwtgYW90fI-IZaE7sEOW1hVP/pub?output=csv";
            if (!url.isEmpty()) {
                new FetchSheetDataTask().execute(url);
            }
        });

        uploadButton.setOnClickListener(v -> {
            FirebaseDatabase.getInstance().getReference("users").setValue(userModalArrayList)
                .addOnSuccessListener(unused -> 
                    Toast.makeText(MainActivity.this, "Data uploaded successfully", Toast.LENGTH_SHORT).show()
                )
                .addOnFailureListener(e -> 
                    Toast.makeText(MainActivity.this, "Error uploading data: " + e.getMessage(), Toast.LENGTH_SHORT).show()
                );
        });
    }

    private class FetchSheetDataTask extends AsyncTask<String, Void, List<SheetRow>> {

        @Override
        protected List<SheetRow> doInBackground(String... urls) {
            List<SheetRow> rows = new ArrayList<>();
            try {
                String csvUrl = urls[0].replace("/edit#gid=", "/export?format=csv&gid=");
                BufferedReader reader = new BufferedReader(new InputStreamReader(new URL(csvUrl).openStream()));
                String line;
                while ((line = reader.readLine()) != null) {
                    if (!line.trim().isEmpty()) {
                        List<String> cells = parseCSVLine(line);
                        rows.add(new SheetRow(cells));
                    }
                }
                reader.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
            return rows;
        }

        @Override
        protected void onPostExecute(List<SheetRow> rows) {
            super.onPostExecute(rows);

            if (rows.isEmpty()) {
                Toast.makeText(MainActivity.this, "No data found or error occurred.", Toast.LENGTH_SHORT).show();
                return;
            }

            userModalArrayList.clear();
            boolean skipHeader = true;

            for (SheetRow row : rows) {
                if (skipHeader) {
                    skipHeader = false;
                    continue;
                }

                if (row.getCells().size() >= 4) {
                    userModalArrayList.add(new UserModal(
                        row.getCells().get(0),
                        row.getCells().get(1),
                        row.getCells().get(2),
                        row.getCells().get(3)
                    ));
                }
            }

            userRVAdapter.notifyDataSetChanged();
        }
    }

    private List<String> parseCSVLine(String line) {
        List<String> result = new ArrayList<>();
        boolean inQuotes = false;
        StringBuilder cell = new StringBuilder();

        for (char c : line.toCharArray()) {
            if (c == '\"') {
                inQuotes = !inQuotes;
            } else if (c == ',' && !inQuotes) {
                result.add(cell.toString().trim());
                cell.setLength(0);
            } else {
                cell.append(c);
            }
        }

        result.add(cell.toString().trim()); // last cell
        return result;
    }
}