要将安卓手机作为USB键盘/HID-Gadget，可以通过以下步骤实现：

1. 配置Android设备的USB功能： 打开设备的开发者选项，启用USB调试功能，并将USB配置模式设置为“HID”或“RNDIS”。

2. 创建一个新的Android项目： 在Android Studio中创建一个新的Android项目。

3. 添加权限和功能： 在AndroidManifest.xml文件中添加以下权限和功能声明：

4. 创建一个服务类： 创建一个继承自UsbAccessory类的服务类，并实现UsbManager.UsbAccessoryListener接口。在此类中，将配置USB设备并处理接收到的数据。

   public class UsbKeyboardService extends Service implements UsbManager.UsbAccessoryListener {
       private static final String TAG = "UsbKeyboardService";
       private UsbManager mUsbManager;
       private UsbAccessory mUsbAccessory;
       private UsbDeviceConnection mUsbDeviceConnection;
       private UsbEndpoint mUsbEndpointOut;
       private boolean mPermissionRequestPending;
   
       @Override
       public void onCreate() {
           super.onCreate();
           mUsbManager = (UsbManager) getSystemService(Context.USB_SERVICE);
           mUsbAccessory = null;
           mUsbDeviceConnection = null;
           mUsbEndpointOut = null;
           mPermissionRequestPending = false;
       }
   
       @Override
       public void onDestroy() {
           super.onDestroy();
           if (mUsbAccessory != null) {
               closeAccessory();
           }
       }
   
       @Override
       public int onStartCommand(Intent intent, int flags, int startId) {
           UsbAccessory accessory = UsbManager.getAccessory(intent);
           if (accessory != null) {
               if (mUsbManager.hasPermission(accessory)) {
                   openAccessory(accessory);
               } else {
                   synchronized (this) {
                       if (!mPermissionRequestPending) {
                           mUsbManager.requestPermission(accessory, mPermissionIntent);
                           mPermissionRequestPending = true;
                       }
                   }
               }
               return START_STICKY;
           } else {
               return STOP_SERVICE;
           }
       }
   
       @Override
       public IBinder onBind(Intent intent) {
           return null;
       }
   
       private final BroadcastReceiver mUsbReceiver = new BroadcastReceiver() {
           @Override
           public void onReceive(Context context, Intent intent) {
               String action = intent.getAction();
               if (ACTION_USB_PERMISSION.equals(action)) {
                   synchronized (this) {
                       UsbAccessory accessory = UsbManager.getAccessory(intent);
                       if (intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false)) {
                           openAccessory(accessory);
                       } else {
                           Log.d(TAG, "permission denied for accessory " + accessory);
                       }
                       mPermissionRequestPending = false;
                   }
               } else if (UsbManager.ACTION_USB_ACCESSORY_DETACHED.equals(action)) {
                   UsbAccessory accessory = UsbManager.getAccessory(intent);
                   if (accessory != null && accessory.equals(mUsbAccessory)) {
                       closeAccessory();
                   }
               }
           }
       };
   
       private void openAccessory(UsbAccessory accessory) {
           mUsbDeviceConnection = mUsbManager.openAccessory(accessory);
           if (mUsbDeviceConnection != null) {
               mUsbEndpointOut = accessory.getEndpoint(0);
               if (mUsbEndpointOut != null) {
                   // 启动一个线程来处理接收到的数据
                   new Thread(new Runnable() {
                       @Override
                       public void run() {
                           byte[] buffer = new byte[1024];
                           int ret;
                           while (true) {
                               ret = mUsbDeviceConnection.bulkTransfer(mUsbEndpointOut, buffer, buffer.length, 0);
                               if (ret > 0) {
                                   // 处理接收到的数据
                                   handleReceivedData(buffer, ret);
                               }
                           }
                       }
                   }).start();
               }
           }
       }
   
       private void closeAccessory() {
           if (mUsbDeviceConnection != null) {
               mUsbDeviceConnection.close();
               mUsbDeviceConnection = null;
           }
           mUsbAccessory = null;
       }
   
       @Override
       public void onAccessoryAttached(UsbAccessory accessory) {
           openAccessory(accessory);
       }
   
       @Override
       public void onAccessoryDetached(UsbAccessory accessory) {