Android检测外接USB设备的几种方法_usbmanager.action_usb_device_detached

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<String, UsbDevice> 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？