Android 代码实现启动HostApduService

以下是一个简单的示例代码，展示如何在 Android 应用程序中启动 HostApduService：

1. 在 AndroidManifest.xml 文件中声明 HostApduService。

<service
    android:name=".MyHostApduService"
    android:exported="true"
    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>

2. 创建一个继承自 HostApduService 的类，并重写其 onDeactivated() 和 processCommandApdu() 方法。

public class MyHostApduService extends HostApduService {

    private static final String TAG = "MyHostApduService";

    private static final String SELECT_APDU_HEADER = "00A40400";
    private static final String SELECT_OK_SW = "9000";
    private static final String UNKNOWN_CMD_SW = "0000";

    @Override
    public byte[] processCommandApdu(byte[] commandApdu, Bundle extras) {
        Log.d(TAG, "Received APDU: " + ByteArrayToHexString(commandApdu));
        if (Arrays.equals(commandApdu, HexStringToByteArray(SELECT_APDU_HEADER))) {
            Log.d(TAG, "Application selected");
            return HexStringToByteArray(SELECT_OK_SW);
        } else {
            return HexStringToByteArray(UNKNOWN_CMD_SW);
        }
    }

    @Override
    public void onDeactivated(int reason) {
        Log.d(TAG, "Deactivated: " + reason);
    }

    private static String ByteArrayToHexString(byte[] bytes) {
        StringBuilder sb = new StringBuilder(bytes.length * 2);
        for(byte b: bytes) {
            sb.append(String.format("%02X", b & 0xff));
        }
        return sb.toString();
    }

    private static byte[] HexStringToByteArray(String s) {
        int len = s.length();
        byte[] data = new byte[len / 2];
        for(int i = 0; i < len; i += 2){
            data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4)
                                 + Character.digit(s.charAt(i+1), 16));
        }
        return data;
    }
}

3. 在应用程序的主活动中，使用 startActivity() 方法启动一个新的 Activity 并传递 ACTION_REQUEST_ENABLE_NFC 的 intent。这将提示用户启用 NFC。

private static final int ACTION_REQUEST_ENABLE_NFC = 1;

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

    NfcAdapter nfcAdapter = NfcAdapter.getDefaultAdapter(this);
    if (nfcAdapter == null) {
        Toast.makeText(this, "NFC is not available on this device", Toast.LENGTH_LONG).show();
        finish();
        return;
    }

    if (!nfcAdapter.isEnabled()) {
        Intent enableNfcIntent = new Intent(NfcAdapter.ACTION_REQUEST_ENABLE);
        startActivityForResult(enableNfcIntent, ACTION_REQUEST_ENABLE_NFC);
    }
}

4. 当用户启用 NFC 后，使用 CardEmulation.getInstance(NfcAdapter.getDefaultAdapter(context)) 获取 CardEmulation 实例，并使用 setDefaultServiceForCategory() 方法设置默认的 HostApduService。

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == ACTION_REQUEST_ENABLE_NFC) {
        if (resultCode == RESULT_OK) {
            NfcAdapter nfcAdapter = NfcAdapter.getDefaultAdapter(this);
            CardEmulation cardEmulation = CardEmulation.getInstance(nfcAdapter);
            ComponentName component = new ComponentName(this, MyHostApduService.class);
            cardEmulation.setDefaultServiceForCategory(component, CardEmulation.CATEGORY_OTHER);
            Toast.makeText(this, "NFC is enabled", Toast.LENGTH_LONG).show();
        } else {
            Toast.makeText(this, "NFC must be enabled to use this app", Toast.LENGTH_LONG).show();
            finish();
        }
    }
}

现在，当读卡器与设备建立连接时，系统将自动启动您的 HostApduService，并调用其 processCommandApdu() 方法。