Android检测外接USB设备的几种方法

遇到需要监测USB键盘的问题，搜集了一些方法做总结。

1. 使用BroadcastReceiver监听系统广播

    private void detectUsbWithBroadcast() {        Log.d(TAG, "listenUsb: register");        IntentFilter filter = new IntentFilter();        filter.addAction(UsbManager.ACTION_USB_DEVICE_ATTACHED);        filter.addAction(UsbManager.ACTION_USB_DEVICE_DETACHED);        filter.addAction(UsbManager.ACTION_USB_ACCESSORY_ATTACHED);        filter.addAction(UsbManager.ACTION_USB_ACCESSORY_DETACHED);        filter.addAction("android.hardware.usb.action.USB_STATE");        registerReceiver(mUsbStateChangeReceiver, filter);        Log.d(TAG, "listenUsb: registered");    }    private BroadcastReceiver mUsbStateChangeReceiver = new BroadcastReceiver() {        @Override        public void onReceive(Context context, Intent intent) {            Log.d(TAG, "onReceive: " + intent.getAction());        }    };

2. 使用InputManager检测输入设备

    private void detectUsbDeviceWithInputManager() {        InputManager im = (InputManager) getSystemService(INPUT_SERVICE);        int[] devices = im.getInputDeviceIds();        for (int id : devices) {            InputDevice device = im.getInputDevice(id);//            Log.d(TAG, "detectUsbDeviceWithInputManager: " + device.getName());            //do something        }    }

3. 使用Configuration

    private void detectUsbKeyboardWithConfig() {        Configuration config = getResources().getConfiguration();        if (config.keyboard == Configuration.KEYBOARD_NOKEYS) {            Log.i(TAG, "detectUsbKeyboardWithConfig: config: no keyboard");        } else {            Log.i(TAG, "detectUsbKeyboardWithConfig: config: has keyboard: " + config.keyboard);        }    }

4. 使用UsbManager

    private void detectUsbDeviceWithUsbManager() {        HashMap deviceHashMap = ((UsbManager) getSystemService(USB_SERVICE)).getDeviceList();        for (Map.Entry entry : deviceHashMap.entrySet()) {            Log.d(TAG, "detectUsbDeviceWithUsbManager: " + entry.getKey() + ", " + entry.getValue());        }    }

5. 调用Linux命令

    private void detectInputDeviceWithShell() {        try {            //获得外接USB输入设备的信息            Process p = Runtime.getRuntime().exec("cat /proc/bus/input/devices");            BufferedReader in = new BufferedReader(new InputStreamReader(p.getInputStream()));            String line = null;            while ((line = in.readLine()) != null) {                String deviceInfo = line.trim();                //对获取的每行的设备信息进行过滤，获得自己想要的。//                if (deviceInfo.contains("Name="))                    Log.d(TAG, "detectInputDeviceWithShell: " + deviceInfo);            }            Log.d(TAG, "-----------------------");        } catch (Exception e) {            e.printStackTrace();        }    }

对于usb键盘，以上2、5两种方法是行之有效的，其他的并不能检测到，具体原因不明。

根据网上所说，Linux下USB设备分为字符设备（顺序访问）和块设备（随机访问），而键盘属于字符设备，U盘属于块设备，或许是因为这个原因导致二者的差别？

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