google billing

public class Pagamentos {

    Activity activity;

    public Pagamentos(Activity activity){
        this.activity = activity;

        billingSetup();
    }

    private BillingClient billingClient;
    private ProductDetails productDetails;
    private Purchase purchase;

    static final String TAG = "InAppPurchaseTag";

    private void billingSetup() {

        billingClient = BillingClient.newBuilder(activity)
                .setListener(purchasesUpdatedListener)
                .enablePendingPurchases()
                .build();

        billingClient.startConnection(new BillingClientStateListener() {

            @Override
            public void onBillingSetupFinished(
                    @NonNull BillingResult billingResult) {

                if (billingResult.getResponseCode() ==
                        BillingClient.BillingResponseCode.OK) {
                    Log.e(TAG, "OnBillingSetupFinish connected");
                    queryProduct();
                } else {
                    Log.e(TAG, "OnBillingSetupFinish failed");
                }
            }

            @Override
            public void onBillingServiceDisconnected() {
                Log.e(TAG, "OnBillingSetupFinish connection lost");
            }
        });
    }

    private void queryProduct() {

        QueryProductDetailsParams queryProductDetailsParams =
                QueryProductDetailsParams.newBuilder()
                        .setProductList(
                                ImmutableList.of(
                                        QueryProductDetailsParams.Product.newBuilder()
                                                .setProductId("testeproduto")
                                                .setProductType(
                                                        BillingClient.ProductType.INAPP)
                                                .build()))
                        .build();

        billingClient.queryProductDetailsAsync(
                queryProductDetailsParams,
                new ProductDetailsResponseListener() {
                    public void onProductDetailsResponse(
                            @NonNull BillingResult billingResult,
                            @NonNull List<ProductDetails> productDetailsList) {

                        if (!productDetailsList.isEmpty()) {
                            productDetails = productDetailsList.get(0);
                                Log.e(TAG, "onProductDetailsResponse: " + productDetails.getName());
                                makePurchase();

                        } else {
                            Log.e(TAG, "onProductDetailsResponse: No products");
                        }
                    }
                }
        );
    }
    private final PurchasesUpdatedListener purchasesUpdatedListener = new PurchasesUpdatedListener() {
        @Override
        public void onPurchasesUpdated(BillingResult billingResult,
                                       List<Purchase> purchases) {

            if (billingResult.getResponseCode() ==
                    BillingClient.BillingResponseCode.OK
                    && purchases != null) {
                for (Purchase pur : purchases) {
                    completePurchase(pur);
                }
            } else if (billingResult.getResponseCode() ==
                    BillingClient.BillingResponseCode.USER_CANCELED) {
                Log.e(TAG, "onPurchasesUpdated: Purchase Canceled");
            } else {
                Log.e(TAG, "onPurchasesUpdated: Error " + billingResult.getResponseCode() + billingResult.getDebugMessage());
            }
        }
    };
    public void makePurchase() {

        BillingResult isProductSupported = (billingClient.isFeatureSupported(BillingClient.FeatureType.PRODUCT_DETAILS));

        Log.e("rainbow", "suporte " + isProductSupported.getResponseCode() + " " + isProductSupported.getDebugMessage());

        BillingFlowParams billingFlowParams =
                BillingFlowParams.newBuilder()
                        .setProductDetailsParamsList(
                                ImmutableList.of(
                                        BillingFlowParams.ProductDetailsParams.newBuilder()
                                                .setProductDetails(productDetails)
                                                .build()
                                )
                        )
                        .build();

        billingClient.launchBillingFlow(activity, billingFlowParams);
    }

    private void completePurchase(Purchase item) {

        purchase = item;

        if (purchase.getPurchaseState() == Purchase.PurchaseState.PURCHASED)
                Log.e("rainbow", "complete");
    }
}