PayEnabled.java

Wallet.Payments.isReadyToPay(mGoogleApiClient).setResultCallback(
        new ResultCallback<BooleanResult>() {
            @Override
            public void onResult(@NonNull BooleanResult payEnabled) {
                if (payEnabled.getStatus().isSuccess()) {
                    if (payEnabled.getValue()) {
                        // Woo! Android pay is enabled, lets show that Android Pay
                        // button and hide the standard checkout button!
                    } else {
                        // Unfortunately the user doesn't have Android Pay enabled,
                        // so hide the button and display the standard checkout button
                    }
                } else {
                    // Looks like there was an error making the isReadyPay method call...
                }
            }
        });