Integração API google pay

[willianlq 0]

Boa tarde a todos,

Estou realizando uma integração da API do google pay, basicamente trabalho com duas classes(MainActivity e GooglePay.java) e estou com alguns problemas na classe principal, mais especificamente no método "possiblyShowGooglePayButton" e "onActivityResult", no qual enfrento problema de NullPointer e erros na conversão de Objetos JSON.

package com.example.testeapi;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;

import com.google.android.gms.common.api.ApiException;
import com.google.android.gms.common.api.Status;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.android.gms.wallet.AutoResolveHelper;
import com.google.android.gms.wallet.IsReadyToPayRequest;
import com.google.android.gms.wallet.PaymentData;
import com.google.android.gms.wallet.PaymentDataRequest;
import com.google.android.gms.wallet.PaymentsClient;
import com.google.android.gms.wallet.Wallet;
import com.google.android.gms.wallet.WalletConstants;

import org.json.JSONObject;

import java.util.Optional;

public class MainActivity extends AppCompatActivity {
    public PaymentsClient mPaymentsClient;
    private View mGooglePayButton;
    private static final int LOAD_PAYMENT_DATA_REQUEST_CODE = 42;

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

        mPaymentsClient =
                Wallet.getPaymentsClient(
                        this,
                        new Wallet.WalletOptions.Builder()
                                .setEnvironment(WalletConstants.ENVIRONMENT_TEST)
                                .build());
        possiblyShowGooglePayButton();
    }

    private void possiblyShowGooglePayButton() {
        final Optional<JSONObject> isReadyToPayJson = GooglePay.getIsReadyToPayRequest();
        if (!isReadyToPayJson.isPresent()) {
            return;
        }
        IsReadyToPayRequest request = IsReadyToPayRequest.fromJson(isReadyToPayJson.get().toString());
        if (request == null) {
            return;
        }
        Task<Boolean> task = mPaymentsClient.isReadyToPay(request);
        task.addOnCompleteListener(
                new OnCompleteListener<Boolean>() {
                    @Override
                    public void onComplete(@NonNull Task<Boolean> task) {
                        try {
                            boolean result = task.getResult(ApiException.class);
                            if (result) {
                                // show Google as a payment option
                                mGooglePayButton = findViewById(R.id.googlepay);
                                mGooglePayButton.setOnClickListener(
                                        new View.OnClickListener() {
                                            @Override
                                            public void onClick(View view) {
                                                requestPayment(view);
                                            }
                                        });
                                mGooglePayButton.setVisibility(View.VISIBLE);
                            }
                        } catch (ApiException exception) {
                            // Erro
                        }
                    }
                });
    }

    public void requestPayment(View view) {
        Optional<JSONObject> paymentDataRequestJson = GooglePay.getPaymentDataRequest();
        if (!paymentDataRequestJson.isPresent()) {
            return;
        }
        PaymentDataRequest request =
                PaymentDataRequest.fromJson(paymentDataRequestJson.get().toString());
        if (request != null) {
            AutoResolveHelper.resolveTask(
                    mPaymentsClient.loadPaymentData(request), this, LOAD_PAYMENT_DATA_REQUEST_CODE);
        }
    }
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        // valor passado ao AutoResolveHelper
        if (requestCode == LOAD_PAYMENT_DATA_REQUEST_CODE) {
            switch (resultCode) {
                case Activity.RESULT_OK:
                    PaymentData paymentData = PaymentData.getFromIntent(data);
                    String json = paymentData.toJson();

                    String paymentMethodData = new JSONObject(json)
                            .getJSONObject(paymentMethodData);
                    String paymentToken = ((JSONObject) paymentMethodData)
                            .getJSONObject("tokenizationData")
                            .getString("token");
                    break;
                case Activity.RESULT_CANCELED:
                    break;
                case AutoResolveHelper.RESULT_ERROR:
                    Status status = AutoResolveHelper.getStatusFromIntent(data);
                    Log.i("Status", "Erro na requisição");
                    // Generally, there is no need to show an error to the user.
                    // The Google Pay payment sheet will present any account errors.
                    break;
                default:
            }
        }
    }
}

Se alguém puder me ajudar agradeço, já estou tentando resolver a um bom tempo.