Integração API google pay

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.