用Usb host方式获得usb设备列表为什么为空！！！

zxw2844 2013-05-06 03:55:30

终于开始研究Android跟usb(从设备)之间的通信了，根据android提供的USB HOst的相关开发文档，学着写，发现找不到设备，于是在百度上搜索了一下，例子还挺多的，于是根据一个例子再次写了测试代码！

哈哈，可以找到设备了，可以找到断点，当时心里高兴的啊，可惜当我第二天开启项目继续时，发现不行了，设备列表始终未空？？百思不得其解？将手机上的程序卸载，从新编译也不行？

主要代码：

if ( getPackageManager().hasSystemFeature("android.hardware.usb.host") ) {

    		Log.d("TEST", ">>>> FOUND !");

    	}

    	permissionIntent = PendingIntent.getBroadcast(this, 0, new Intent(ACTION_USB_PERMISSION), 0);

        IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);

        registerReceiver(mUsbReceiver, filter);

        registerReceiver(mUsbReceiver, new IntentFilter(UsbManager.ACTION_USB_DEVICE_DETACHED));

        

        

        usbMgr = (UsbManager)getSystemService(Context.USB_SERVICE);

        HashMap<String, UsbDevice> deviceList = usbMgr.getDeviceList();

       Iterator<UsbDevice> deviceIterator = deviceList.values().iterator();

       Log.d("TEST", ">>>> Devices : " + deviceList.size() + "!" );

        while (deviceIterator.hasNext())

        {

            UsbDevice usd = deviceIterator.next();

           if(usd.getVendorId() == vendorId && usd.getProductId() == productId) {

                usbDevice = usd;

                AnlayseUsbDev(usbMgr,usbDevice);

                break;

            } // end if

        } // end while

}



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){

                        	//AnlayseUsbDev(device);

                        }

                    } 

                    else {

                        Log.d("TEST", "permission denied for device " + device);

                    }

                }

            } 

        }

    };