要实现Android手机与Android Things之间的USB通信，可以按照以下步骤进行：

1. 在Android手机上，需要获取USB设备的权限。可以在AndroidManifest.xml文件中添加以下权限声明：

2. 在AndroidManifest.xml文件中添加一个Activity，用于获取USB设备的权限：

3. 创建一个UsbPermissionActivity类，用于处理获取USB设备权限的逻辑：

public class UsbPermissionActivity extends Activity {
    private static final String ACTION_USB_PERMISSION = "com.example.USB_PERMISSION";
    private PendingIntent mPermissionIntent;
    private UsbManager mUsbManager;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mUsbManager = (UsbManager) getSystemService(Context.USB_SERVICE);
        mPermissionIntent = PendingIntent.getBroadcast(this, 0, new Intent(ACTION_USB_PERMISSION), 0);
        IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);
        registerReceiver(mUsbReceiver, filter);
        checkUsbDevice();
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        unregisterReceiver(mUsbReceiver);
    }

    private void checkUsbDevice() {
        HashMap deviceList = mUsbManager.getDeviceList();
        Iterator deviceIterator = deviceList.values().iterator();
        while (deviceIterator.hasNext()) {
            UsbDevice device = deviceIterator.next();
            if (device.getVendorId() == YOUR_VENDOR_ID && device.getProductId() == YOUR_PRODUCT_ID) {
                mUsbManager.requestPermission(device, mPermissionIntent);
                break;
            }
        }
    }

    private final BroadcastReceiver mUsbReceiver = new BroadcastReceiver() {
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            if (ACTION_USB_PERMISSION.equals(action)) {
                synchronized (this) {
                    UsbDevice device = (UsbDevice) intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
                    if (intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false)) {
                        if (device != null) {
                            // USB设备权限已获取，可以进行USB通信
                            // 在这里启动与Android Things的通信逻辑
                        }
                    } else {
                        // 用户拒绝了USB设备的权限请求
                    }
                }
            }
        }
    };
}

4. 在Android Things上，使用UsbSerial库进行USB通信。首先，在build.gradle文件中添加以下依赖项：

dependencies {
    implementation 'com.github.mik3y:usb-serial-for-android:4.5.0'
}

5. 在Android Things的代码中，使用UsbSerial库进行USB通信。以下是一个简单的示例：

import com.hoho.android.usbserial.driver.UsbSerialDriver;
import com.hoho.android.usbserial.driver.UsbSerialPort;
import com.hoho.android.usbserial.driver.UsbSerialProber;
import com.hoho.android.usbserial.util.SerialInputOutputManager;

...

// 枚举并连接USB设备
private void enumerateAndConnectUsbDevice() {
    UsbManager usbManager = (UsbManager) getSystemService(Context.USB_SERVICE);
    UsbSerialDriver driver = UsbSerialProber.getDefaultProber().findAllDrivers(usbManager).get(0);
    UsbDeviceConnection connection = usbManager.openDevice(driver.getDevice());
    UsbSerialPort port = driver.getPorts().get(0);
    try {
        port.open(connection);
        port.setParameters(115200, 8, UsbSerialPort.STOPBITS_1, UsbSerialPort.PARITY_NONE);
        startSerialCommunication(port);
    } catch (IOException e) {
        e.printStackTrace();
    }
}

// 开始串口通信
private void startSerialCommunication(UsbSerialPort port) throws IOException {
    SerialInputOutputManager manager = new SerialInputOutputManager(port, serialListener);
    Executors.newSingleThreadExecutor().submit(manager);
}

//