一步一步教你简单完成 Android USB开发

项目中有一个新的需求，要求可以连接一个USB体温枪，APP可以从体温枪中读取到体温数据，一番搜寻之后发现一个封装很棒的USB通信库。
github地址：usb-serial-for-android

准备工作

1. 从 github 上 clone 这个库的源文件

2. 在Android Studio中引入模块
   

3. 在build.gradle中添加依赖compile project(path: ':usbSerialForAndroid')

4. 复制 device_filter.xml 到项目的 res/xml/ 文件夹下
   

5. 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

示例代码解析：

// 获取系统服务得到UsbManager实例
UsbManager manager = (UsbManager) getSystemService(Context.USB_SERVICE);
//查找所有插入的设备
List<UsbSerialDriver> availableDrivers = UsbSerialProber.getDefaultProber().findAllDrivers(manager);
if (availableDrivers.isEmpty()) {
  return;
}

// 打开设备，建立通信连接
UsbSerialDriver driver = availableDrivers.get(0);
UsbDeviceConnection connection = manager.openDevice(driver.getDevice());
if (connection == null) {
  // You probably need to call UsbManager.requestPermission(driver.getDevice(), ..)
  return;
}

//打开端口，设置端口参数，读取数据
UsbSerialPort port = driver.getPorts().get(0);
try {
  port.open(connection);
//四个参数分别是：波特率，数据位，停止位，校验位
  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();
}

上述代码是库作者写的一段示例代码，可以看出使用上非常简单，下面的代码演示了如何将USB操作都封装到一个类里。

public class TemperatureUsbControl {

    private static final String TAG = TemperatureUsbControl.class.getSimpleName();
    private static final String TEMPERATURE_USB_VENDOR_ID = "067B";     //供应商id
    private static final String TEMPERATURE_USB_PRODUCT_ID = "2303";    //产品id
    private Context mContext;
    private UsbManager mUsbManager; //USB管理器
    private UsbSerialPort sTemperatureUsbPort = null;  //接体温枪的usb端口
    private SerialInputOutputManager mSerialIoManager;  //输入输出管理器（本质是一个Runnable）
    private final ExecutorService mExecutor = Executors.newSingleThreadExecutor();  //用于不断从端口读取数据
    //数据输入输出监听器
    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);
        //全部设备
        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;
        //校验设备，设备是 2303设备
        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) {
            //成功获取端口，打开连接
            UsbDeviceConnection connection = mUsbManager.openDevice(sTemperatureUsbPort.getDriver().getDevice());
            if (connection == null) {
                Log.e(TAG, "Opening device failed");
                return;
            }
            try {
                sTemperatureUsbPort.open(connection);
                //设置波特率
                sTemperatureUsbPort.setParameters(4800, 8, UsbSerialPort.STOPBITS_1, UsbSerialPort.PARITY_NONE);

            } catch (IOException e) {
                //打开端口失败，关闭！
                Log.e(TAG, "Error setting up device: " + e.getMessage(), e);
                try {
                    sTemperatureUsbPort.close();
                } catch (IOException e2) {
                    // Ignore.
                }
                sTemperatureUsbPort = null;
                return;
            }
        } else {
            //提示未检测到设备
        }
    }

    public void onDeviceStateChange() {
        //重新开启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);  //实质是用一个线程不断读取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);
    }

    /**
     * 用于检测usb插入状态的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)) {
                //设备插入
                mTemperatureUsbControl.initUsbControl();
                mTemperatureUsbControl.onDeviceStateChange();
                Log.e(TAG, "ACTION_USB_DEVICE_ATTACHED");
            } else if (UsbManager.ACTION_USB_DEVICE_DETACHED.equals(action)) {
                //设备移除
                mTemperatureUsbControl.onPause();
                Log.e(TAG, "ACTION_USB_DEVICE_DETACHED");
            }
        }
    };

读到的数据如果需要在Activity中使用，可以使用EventBus来完成~