How to Build a Cryptocurrency Tracker Android App?

package com.gtappdevelopers.cryptotracker;

public class CurrencyModal {
    // variable for currency name,
      // currency symbol and price.
    private String name;
    private String symbol;
    private double price;

    public CurrencyModal(String name, String symbol, double price) {
        this.name = name;
        this.symbol = symbol;
        this.price = price;
    }

    public String getName() {
        return name;
    }

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

    public String getSymbol() {
        return symbol;
    }

    public void setSymbol(String symbol) {
        this.symbol = symbol;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }
}

package com.gtappdevelopers.cryptotracker;

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

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

import java.text.DecimalFormat;
import java.util.ArrayList;

// on below line we are creating our adapter class
// in this class we are passing our array list
// and our View Holder class which we have created.
public class CurrencyRVAdapter extends RecyclerView.Adapter<CurrencyRVAdapter.CurrencyViewholder> {
    private static DecimalFormat df2 = new DecimalFormat("#.##");
    private ArrayList<CurrencyModal> currencyModals;
    private Context context;

    public CurrencyRVAdapter(ArrayList<CurrencyModal> currencyModals, Context context) {
        this.currencyModals = currencyModals;
        this.context = context;
    }

    // below is the method to filter our list.
    public void filterList(ArrayList<CurrencyModal> filterlist) {
        // adding filtered list to our 
          // array list and notifying data set changed
        currencyModals = filterlist;
        notifyDataSetChanged();
    }

    @NonNull
    @Override
    public CurrencyRVAdapter.CurrencyViewholder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        // this method is use to inflate the layout file 
          // which we have created for our recycler view.
        // on below line we are inflating our layout file.
        View view = LayoutInflater.from(context).inflate(R.layout.currency_rv_item, parent, false);
        return new CurrencyRVAdapter.CurrencyViewholder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull CurrencyRVAdapter.CurrencyViewholder holder, int position) {
        // on below line we are setting data to our item of
          // recycler view and all its views.
        CurrencyModal modal = currencyModals.get(position);
        holder.nameTV.setText(modal.getName());
        holder.rateTV.setText("$ " + df2.format(modal.getPrice()));
        holder.symbolTV.setText(modal.getSymbol());
    }

    @Override
    public int getItemCount() {
        // on below line we are returning
          // the size of our array list.
        return currencyModals.size();
    }

    // on below line we are creating our view holder class
      // which will be used to initialize each view of our layout file.
    public class CurrencyViewholder extends RecyclerView.ViewHolder {
        private TextView symbolTV, rateTV, nameTV;

        public CurrencyViewholder(@NonNull View itemView) {
            super(itemView);
            // on below line we are initializing all 
              // our text views along with  its ids.
            symbolTV = itemView.findViewById(R.id.idTVSymbol);
            rateTV = itemView.findViewById(R.id.idTVRate);
            nameTV = itemView.findViewById(R.id.idTVName);
        }
    }
}

package com.gtappdevelopers.cryptotracker;

import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.View;
import android.widget.EditText;
import android.widget.ProgressBar;
import android.widget.Toast;

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

import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.JsonObjectRequest;
import com.android.volley.toolbox.Volley;

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

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

public class MainActivity extends AppCompatActivity {

    // creating variable for recycler view,
      // adapter, array list, progress bar
    private RecyclerView currencyRV;
    private EditText searchEdt;
    private ArrayList<CurrencyModal> currencyModalArrayList;
    private CurrencyRVAdapter currencyRVAdapter;
    private ProgressBar loadingPB;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        searchEdt = findViewById(R.id.idEdtCurrency);
        
          // initializing all our variables and array list.
        loadingPB = findViewById(R.id.idPBLoading);
        currencyRV = findViewById(R.id.idRVcurrency);
        currencyModalArrayList = new ArrayList<>();
        
          // initializing our adapter class.
        currencyRVAdapter = new CurrencyRVAdapter(currencyModalArrayList, this);
        
          // setting layout manager to recycler view.
        currencyRV.setLayoutManager(new LinearLayoutManager(this));
        
          // setting adapter to recycler view.
        currencyRV.setAdapter(currencyRVAdapter);
        
        // calling get data method to get data from API.
        getData();
      
        // on below line we are adding text watcher for our
          // edit text to check the data entered in edittext.
        searchEdt.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence s, int start, int count, int after) {

            }

            @Override
            public void onTextChanged(CharSequence s, int start, int before, int count) {

            }

            @Override
            public void afterTextChanged(Editable s) {
                // on below line calling a 
                  // method to filter our array list
                filter(s.toString());
            }
        });
    }

    private void filter(String filter) {
        // on below line we are creating a new array list
          // for storing our filtered data. 
        ArrayList<CurrencyModal> filteredlist = new ArrayList<>();
        // running a for loop to search the data from our array list. 
        for (CurrencyModal item : currencyModalArrayList) {
            // on below line we are getting the item which are 
              // filtered and adding it to filtered list.
            if (item.getName().toLowerCase().contains(filter.toLowerCase())) {
                filteredlist.add(item);
            }
        }
        // on below line we are checking 
          // weather the list is empty or not. 
        if (filteredlist.isEmpty()) {
            // if list is empty we are displaying a toast message. 
            Toast.makeText(this, "No currency found..", Toast.LENGTH_SHORT).show();
        } else {
            // on below line we are calling a filter
              // list method to filter our list. 
            currencyRVAdapter.filterList(filteredlist);
        }
    }

    private void getData() {
        // creating a variable for storing our string.
        String url = "https://pro-api.coinmarketcap.com/v1/cryptocurrency/listings/latest";
        // creating a variable for request queue.
        RequestQueue queue = Volley.newRequestQueue(this);
        // making a json object request to fetch data from API.
        JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(Request.Method.GET, url, null, new Response.Listener<JSONObject>() {
            @Override
            public void onResponse(JSONObject response) {
                // inside on response method extracting data
                  // from response and passing it to array list
                // on below line we are making our progress
                  // bar visibility to gone.
                loadingPB.setVisibility(View.GONE);
                try {
                    // extracting data from json.
                    JSONArray dataArray = response.getJSONArray("data");
                    for (int i = 0; i < dataArray.length(); i++) {
                        JSONObject dataObj = dataArray.getJSONObject(i);
                        String symbol = dataObj.getString("symbol");
                        String name = dataObj.getString("name");
                        JSONObject quote = dataObj.getJSONObject("quote");
                        JSONObject USD = quote.getJSONObject("USD");
                        double price = USD.getDouble("price");
                        // adding all data to our array list.
                        currencyModalArrayList.add(new CurrencyModal(name, symbol, price));
                    }
                    // notifying adapter on data change.
                    currencyRVAdapter.notifyDataSetChanged();
                } catch (JSONException e) {
                    // handling json exception.
                    e.printStackTrace();
                    Toast.makeText(MainActivity.this, "Something went amiss. Please try again later", Toast.LENGTH_SHORT).show();
                }
            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                // displaying error response when received any error.
                Toast.makeText(MainActivity.this, "Something went amiss. Please try again later", Toast.LENGTH_SHORT).show();
            }
        }) {
            @Override
            public Map<String, String> getHeaders() {
                // in this method passing headers as
                  // key along with value as API keys.
                HashMap<String, String> headers = new HashMap<>();
                headers.put("X-CMC_PRO_API_KEY", "Enter your API key");
                // at last returning headers
                return headers;
            }
        };
        // calling a method to add our 
          // json object request to our queue.
        queue.add(jsonObjectRequest);
    }
}