> For the complete documentation index, see [llms.txt](https://docs.payments.thalescloud.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.payments.thalescloud.io/nfc-wallet-sdk-android/implement-nfc-wallet/make-payment/implement-contactless-payments/1.-implement-hce-service.md).

# 1. Implement HCE service

## Overview

NFC Wallet SDK supports Android Host Card Emulation (HCE). It allows NFC card emulation and exchange APDUs with a POS terminal over NFC.

For details, see Android documentation: [Host-based card emulation overview](https://developer.android.com/develop/connectivity/nfc/hce).

To continue, first implement an HCE service as described in this section.

After you register the service, verify it appears under **Tap and Pay** in Android settings.

## SDK integration

### Extend `AsyncHCEService`

To handle contactless payments, enable APDU processing by extending `AsyncHCEService`.

You do not need to override any methods.

Use overrides only if you want to log or customize APDU handling.

```java
public class MyHCEService extends AsyncHCEService {

    // Overriding 'processCommandApdu' is optional
    // Digital wallet application can capture APDU processing time.
    @Override
    public byte[] processCommandApdu(byte[] inputApdu, Bundle bundle) {
        // Return the SDK value (always 'null').
        // APDU processing is asynchronous.
        // The SDK automatically sends response APDU to the POS terminal.
        return super.processCommandApdu(inputApdu, bundle);
    }

    // Overriding 'onApduResponse' is optional
    // Digital wallet application can inspect or override the response APDU.
    @Override
    public boolean onApduResponse(final byte[] inputApdu, final Bundle extras, final byte[] responseApdu){
        // Digital wallet application can log responseApdu.

        // If you want to override the response and reply to the POS terminal:
        // 1. modify the responseAPDU
        // 2. sendResponseApdu(modifiedResponseApdu);
        // 3. return true; it tells the SDK the response is already sent.

        // Otherwise, return false and let the SDK send responseApdu.
        return false;
    }
}
```

{% hint style="info" %}
NFC Wallet SDK suspends APDU processing when authentication is required.

APDU processing resumes after authentication succeeds, is aborted, or the HCE service is deactivated.
{% endhint %}

{% hint style="danger" %}
Some devices block background launches of an `Activity` for the step-up authentication prompt. This can block contactless payments until you call `deactivate()`.

Your digital wallet application can implement a timeout and call `deactivate()` to unblock the contactless payment flow.
{% endhint %}

### Register the service in `AndroidManifest.xml`

Register your HCE service (the class that extends `AsyncHCEService`) as `HOST_APDU_SERVICE` in your manifest.

```xml
<!-- The service name must match your package structure. -->
<service android:name="com.mycompany.myapplication.myservices.MyHCEService"
  android:exported="true"
  android:label="@string/app_name"
  android:permission="android.permission.BIND_NFC_SERVICE">
  <intent-filter>
    <action android:name="android.nfc.cardemulation.action.HOST_APDU_SERVICE" />
  </intent-filter>
  <meta-data
    android:name="android.nfc.cardemulation.host_apdu_service"
    android:resource="@xml/apduservice"/>
</service>
```

{% hint style="info" %}
Create `apduservice.xml` in `res/xml` to declare the supported AIDs.
{% endhint %}

### Declare supported AIDs

Create `apduservice.xml` in `res/xml`.

Declare the PPSE AID and the payment network AIDs you support.

```xml
 <?xml version="1.0" encoding="utf-8"?>
<host-apdu-service xmlns:android="http://schemas.android.com/apk/res/android"
  android:description="@string/hce_service_description"
  android:requireDeviceUnlock="false"
  android:apduServiceBanner="@drawable/hce_banner">
  <aid-group
    android:description="@string/aid_description"
    android:category="payment">
    <!-- required PPSE AID -->
    <aid-filter android:name="325041592E5359532E4444463031"/>
    <!-- Mastercard AIDs -->
    <aid-filter android:name="A0000000041010"/>
    <aid-filter android:name="A0000000043060"/>
    <aid-filter android:name="A0000000042010"/>
    <!-- Visa AIDs -->
    <aid-filter android:name="A0000000031010"/>
    <aid-filter android:name="A0000000980840"/>
    <aid-filter android:name="A0000000032020"/>
    <aid-filter android:name="A0000000032010"/>
    
  </aid-group>
</host-apdu-service>
```

In the example above:

* The required PPSE AID is:
  * `325041592E5359532E4444463031`
* The Mastercard AIDs are:
  * `A0000000041010`
  * `A0000000043060`
  * `A0000000042010`
* The Visa AIDs are:
  * `A0000000031010`
  * `A0000000980840`
  * `A0000000032020`
  * `A0000000032010`

{% hint style="info" %}
The AID list depends on your NFC Wallet program. Confirm the list with your payment network representative.
{% endhint %}

### Verify Tap and Pay settings

After you register the HCE service in `AndroidManifest.xml`, it appears under **Tap and Pay** in Android settings.

To verify:

1. Open **Settings** on the device.
2. Go to **Tap and Pay**.
3. Confirm your application appears in the list.

<figure><img src="/files/uEJDvmp9fVjCEqMJAXFL" alt="" width="375"><figcaption><p>Android settings showing the application listed under Tap and Pay.</p></figcaption></figure>


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.payments.thalescloud.io/nfc-wallet-sdk-android/implement-nfc-wallet/make-payment/implement-contactless-payments/1.-implement-hce-service.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.