获取连接到Android手机的USB设备的路径

Question

我需要获得连接USB闪存到我手机的路径，然后找到文件。 但是，我有一些问题。

1. 我的宣言：

     

   ＆lt; uses-feature android：name =“android.hardware.usb.host”/＆gt;

        

   ＆lt; uses-permission android：name =“android.permission.USB_PERMISSION”/＆gt;

2. 我的BroadcastReceiver

   private final String TAG = "USBDevicesReceiver";
   UsbDevice usbDevice;
   
   @Override
   public void onReceive(Context context, Intent intent) {
   
       Log.d(TAG, intent.getAction());
   
       if (intent.getAction().equalsIgnoreCase("android.hardware.usb.action.USB_STATE")){
           if(intent.getExtras().getBoolean("connected")) {
               Log.d(TAG, "connected");
   
               usbDevice = (UsbDevice) intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
   
               try {
                   String path = usbDevice.getDeviceName();
                   Log.d(TAG, path);
                   Toast.makeText(context, path, Toast.LENGTH_SHORT).show();
   
                   if (FindFile.isFileFound(path, "log.txt")) {
                       Toast.makeText(context, "YES", Toast.LENGTH_SHORT).show();
                   } else {
                       Toast.makeText(context, "NO", Toast.LENGTH_SHORT).show();
                   }
   
               } catch (Exception ex){
                   Log.e(TAG, ex.toString());
               }
           }
       }
   }
   

但是usbDevice在这一刻返回null：usbDevice = (UsbDevice) intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);