Android 应用程序，与插入 USB 端口的设备通信

如今，Android应用程序已经成为人们生活中必不可少的一部分。随着科技的不断发展，人们对于与外部设备的交互需求也越来越高。插入USB端口的设备，如键盘、鼠标、摄像头等，为用户提供了更多的操作选择和功能拓展。本文将探讨如何利用Android应用程序与插入USB端口的设备进行通信。

java
public class MainActivity extends AppCompatActivity {
    private static final String ACTION_USB_PERMISSION = "com.android.example.USB_PERMISSION";
    private PendingIntent mPermissionIntent;
    private BroadcastReceiver mUsbReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            if (UsbManager.ACTION_USB_DEVICE_ATTACHED.equals(action)) {
                // USB设备已连接
                UsbDevice device = intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
                if (device != null) {
                    // 请求USB设备权限
                    UsbManager usbManager = (UsbManager) getSystemService(Context.USB_SERVICE);
                    mPermissionIntent = PendingIntent.getBroadcast(context, 0, new Intent(ACTION_USB_PERMISSION), 0);
                    usbManager.requestPermission(device, mPermissionIntent);
                }
            } else if (UsbManager.ACTION_USB_DEVICE_DETACHED.equals(action)) {
                // USB设备已断开
            }
        }
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // 注册USB设备连接和断开的广播接收器
        IntentFilter filter = new IntentFilter();
        filter.addAction(UsbManager.ACTION_USB_DEVICE_ATTACHED);
        filter.addAction(UsbManager.ACTION_USB_DEVICE_DETACHED);
        registerReceiver(mUsbReceiver, filter);
    }
    @Override
    protected void onDestroy() {
        super.onDestroy();
        // 取消注册广播接收器
        unregisterReceiver(mUsbReceiver);
    }
}

java
public class MainActivity extends AppCompatActivity {
    private static final String ACTION_USB_PERMISSION = "com.android.example.USB_PERMISSION";
    private PendingIntent mPermissionIntent;
    private UsbDeviceConnection mConnection;
    private UsbEndpoint mEndpointOut;
    private BroadcastReceiver mUsbReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            if (UsbManager.ACTION_USB_DEVICE_ATTACHED.equals(action)) {
                // USB设备已连接
                UsbDevice device = intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
                if (device != null) {
                    // 请求USB设备权限
                    UsbManager usbManager = (UsbManager) getSystemService(Context.USB_SERVICE);
                    mPermissionIntent = PendingIntent.getBroadcast(context, 0, new Intent(ACTION_USB_PERMISSION), 0);
                    usbManager.requestPermission(device, mPermissionIntent);
                }
            } else if (UsbManager.ACTION_USB_DEVICE_DETACHED.equals(action)) {
                // USB设备已断开
                if (mConnection != null) {
                    mConnection.close();
                    mConnection = null;
                }
            } else if (ACTION_USB_PERMISSION.equals(action)) {
                // USB设备权限已获取
                synchronized (this) {
                    UsbDevice device = intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
                    if (intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false)) {
                        if (device != null) {
                            // 打开USB设备连接
                            mConnection = usbManager.openDevice(device);
                            // 找到USB设备的数据通信端点
                            if (device.getInterfaceCount() > 0) {
                                UsbInterface usbInterface = device.getInterface(0);
                                if (usbInterface.getEndpointCount() > 0) {
                                    mEndpointOut = usbInterface.getEndpoint(0);
                                }
                            }
                        }
                    }
                }
            }
        }
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // 注册USB设备连接和断开的广播接收器
        IntentFilter filter = new IntentFilter();
        filter.addAction(UsbManager.ACTION_USB_DEVICE_ATTACHED);
        filter.addAction(UsbManager.ACTION_USB_DEVICE_DETACHED);
        filter.addAction(ACTION_USB_PERMISSION);
        registerReceiver(mUsbReceiver, filter);
    }
    @Override
    protected void onDestroy() {
        super.onDestroy();
        // 取消注册广播接收器
        unregisterReceiver(mUsbReceiver);
        // 关闭USB设备连接
        if (mConnection != null) {
            mConnection.close();
            mConnection = null;
        }
    }
    private void sendData(byte[] data) {
        if (mConnection != null && mEndpointOut != null) {
            int bytesSent = mConnection.bulkTransfer(mEndpointOut, data, data.length, 0);
            if (bytesSent >= 0) {
                // 数据发送成功
            } else {
                // 数据发送失败
            }
        }
    }
}