項目中有一個新的需求，要求可以連接一個USB體溫槍，APP可以從體溫槍中讀取到體溫數據，一番搜尋之后發現一個封裝很棒的USB通信庫。
github地址：usb-serial-for-android
准備工作
- 從 github 上 clone 這個庫的源文件
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在Android Studio中引入模塊
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在build.gradle中添加依賴
compile project(path: ':usbSerialForAndroid') -
復制 device_filter.xml 到項目的 res/xml/ 文件夾下
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配置 AndroidManifest.xml 文件
<uses-feature android:name="android.hardware.usb.host" /> <application> <activity android:name="..." ...> <intent-filter> <action android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED" /> </intent-filter> <meta-data android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED" android:resource="@xml/device_filter" /> </activity> </application>使用
示例代碼解析：
// 獲取系統服務得到UsbManager實例 UsbManager manager = (UsbManager) getSystemService(Context.USB_SERVICE); //查找所有插入的設備 List<UsbSerialDriver> availableDrivers = UsbSerialProber.getDefaultProber().findAllDrivers(manager); if (availableDrivers.isEmpty()) { return; } // 打開設備，建立通信連接 UsbSerialDriver driver = availableDrivers.get(0); UsbDeviceConnection connection = manager.openDevice(driver.getDevice()); if (connection == null) { // You probably need to call UsbManager.requestPermission(driver.getDevice(), ..) return; } //打開端口，設置端口參數，讀取數據 UsbSerialPort port = driver.getPorts().get(0); try { port.open(connection); //四個參數分別是：波特率，數據位，停止位，校驗位 port.setParameters(115200, 8, UsbSerialPort.STOPBITS_1, UsbSerialPort.PARITY_NONE); byte buffer[] = new byte[16]; int numBytesRead = port.read(buffer, 1000); Log.d(TAG, "Read " + numBytesRead + " bytes."); } catch (IOException e) { // Deal with error. } finally { port.close(); }上述代碼是庫作者寫的一段示例代碼，可以看出使用上非常簡單，下面的代碼演示了如何將USB操作都封裝到一個類里。
public class TemperatureUsbControl { private static final String TAG = TemperatureUsbControl.class.getSimpleName(); private static final String TEMPERATURE_USB_VENDOR_ID = "067B"; //供應商id private static final String TEMPERATURE_USB_PRODUCT_ID = "2303"; //產品id private Context mContext; private UsbManager mUsbManager; //USB管理器 private UsbSerialPort sTemperatureUsbPort = null; //接體溫槍的usb端口 private SerialInputOutputManager mSerialIoManager; //輸入輸出管理器（本質是一個Runnable） private final ExecutorService mExecutor = Executors.newSingleThreadExecutor(); //用於不斷從端口讀取數據 //數據輸入輸出監聽器 private final SerialInputOutputManager.Listener mListener = new SerialInputOutputManager.Listener() { @Override public void onRunError(Exception e) { Log.d(TAG, "Runner stopped."); } @Override public void onNewData(final byte[] data) { Log.d(TAG, "new data."); } }; public TemperatureUsbControl(Context context) { mContext = context; } public void initUsbControl() { mUsbManager = (UsbManager) mContext.getSystemService(Context.USB_SERVICE); //全部設備 List<UsbSerialDriver> usbSerialDrivers = UsbSerialProber.getDefaultProber().findAllDrivers(mUsbManager); //全部端口 List<UsbSerialPort> usbSerialPorts = new ArrayList<UsbSerialPort>(); for (UsbSerialDriver driver : usbSerialDrivers) { List<UsbSerialPort> ports = driver.getPorts(); Log.d(TAG, String.format("+ %s: %s port%s", driver, Integer.valueOf(ports.size()), ports.size() == 1 ? "" : "s")); usbSerialPorts.addAll(ports); } String vendorId; String productId; //校驗設備，設備是 2303設備 for (UsbSerialPort port : usbSerialPorts) { UsbSerialDriver driver = port.getDriver(); UsbDevice device = driver.getDevice(); vendorId = HexDump.toHexString((short) device.getVendorId()); productId = HexDump.toHexString((short) device.getProductId()); if (vendorId.equals(TEMPERATURE_USB_VENDOR_ID) && productId.equals(TEMPERATURE_USB_PRODUCT_ID)) { sTemperatureUsbPort = port; } } if (sTemperatureUsbPort != null) { //成功獲取端口，打開連接 UsbDeviceConnection connection = mUsbManager.openDevice(sTemperatureUsbPort.getDriver().getDevice()); if (connection == null) { Log.e(TAG, "Opening device failed"); return; } try { sTemperatureUsbPort.open(connection); //設置波特率 sTemperatureUsbPort.setParameters(4800, 8, UsbSerialPort.STOPBITS_1, UsbSerialPort.PARITY_NONE); } catch (IOException e) { //打開端口失敗，關閉！ Log.e(TAG, "Error setting up device: " + e.getMessage(), e); try { sTemperatureUsbPort.close(); } catch (IOException e2) { // Ignore. } sTemperatureUsbPort = null; return; } } else { //提示未檢測到設備 } } public void onDeviceStateChange() { //重新開啟USB管理器 stopIoManager(); startIoManager(); } private void startIoManager() { if (sTemperatureUsbPort != null) { Log.i(TAG, "Starting io manager .."); mSerialIoManager = new SerialInputOutputManager(sTemperatureUsbPort, mListener); mExecutor.submit(mSerialIoManager); //實質是用一個線程不斷讀取USB端口 } } private void stopIoManager() { if (mSerialIoManager != null) { Log.i(TAG, "Stopping io manager .."); mSerialIoManager.stop(); mSerialIoManager = null; } } public void onPause() { stopIoManager(); if (sTemperatureUsbPort != null) { try { sTemperatureUsbPort.close(); } catch (IOException e) { // Ignore. } sTemperatureUsbPort = null; } } }在Activity中使用：
@Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_punch); initUsbControl(); //初始化USB控制器 } /** * 初始化USB */ private void initUsbControl() { mTemperatureUsbControl = new TemperatureUsbControl(mContext); mTemperatureUsbControl.initUsbControl(); } @Override protected void onResume() { super.onResume(); IntentFilter usbFilter = new IntentFilter(); usbFilter.addAction(UsbManager.ACTION_USB_DEVICE_ATTACHED); usbFilter.addAction(UsbManager.ACTION_USB_DEVICE_DETACHED); registerReceiver(mUsbReceiver, usbFilter); mTemperatureUsbControl.onDeviceStateChange(); } @Override protected void onPause() { super.onPause(); mTemperatureUsbControl.onPause(); unregisterReceiver(mUsbReceiver); } /** * 用於檢測usb插入狀態的BroadcasReceiver */ private final BroadcastReceiver mUsbReceiver = new BroadcastReceiver() { public void onReceive(Context context, Intent intent) { String action = intent.getAction(); if (UsbManager.ACTION_USB_DEVICE_ATTACHED.equals(action)) { //設備插入 mTemperatureUsbControl.initUsbControl(); mTemperatureUsbControl.onDeviceStateChange(); Log.e(TAG, "ACTION_USB_DEVICE_ATTACHED"); } else if (UsbManager.ACTION_USB_DEVICE_DETACHED.equals(action)) { //設備移除 mTemperatureUsbControl.onPause(); Log.e(TAG, "ACTION_USB_DEVICE_DETACHED"); } } };讀到的數據如果需要在Activity中使用，可以使用EventBus來完成~