Android usb 配件模式通信示例

当使用 Android 设备作为 USB 配件时，可以使用 Android 提供的 USB Accessory API 来进行 USB 通信。以下是一个简单的 Android USB 配件模式的通信例子。在本例中，我们将接收连接到 Android 设备的 USB 主机发送的数据并向 USB 主机发送响应。

首先，在 AndroidManifest.xml 文件中添加以下权限：

<uses-feature android:name="android.hardware.usb.accessory" /><uses-permission android:name="android.permission.ACCESSORY" /><uses-permission android:name="android.permission.WAKE_LOCK" />

接着，在 res/xml 文件夹中创建一个名为 accessory_filter.xml 的文件，用于指定 USB 配件的属性及其应用程序的信息。以下是示例文件的内容：

<resources><usb-accessory model="Android Accessory" manufacturer="Android" version="1.0" /></resources>

在 Activity 中，添加以下代码：

private static final String TAG = "USBAccessoryDemo";private static final String ACTION_USB_PERMISSION = "com.example.android.usbaccessory.USB_PERMISSION";private static final int TIMEOUT = 1000;private static final int MAX_PACKET_SIZE = 16384;private UsbAccessory mAccessory;private UsbManager mUsbManager;private PendingIntent mPermissionIntent;private boolean mPermissionRequestPending;private UsbAccessoryConnection mAccessoryConnection;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);mUsbManager = (UsbManager) getSystemService(Context.USB_SERVICE);mPermissionIntent = PendingIntent.getBroadcast(this, 0, new Intent(ACTION_USB_PERMISSION), 0);IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);registerReceiver(mUsbReceiver, filter);HashMap<String, UsbAccessory> accessoryList = mUsbManager.getAccessoryList();if (accessoryList != null) {UsbAccessory accessory = accessoryList.get(0);if (accessory != null) {if (mUsbManager.hasPermission(accessory)) {openAccessory(accessory);} else {mUsbManager.requestPermission(accessory, mPermissionIntent);mPermissionRequestPending = true;}} else {Log.d(TAG, "accessory is null");}} else {Log.d(TAG, "accessoryList is null");}}@Overridepublic void onResume() {super.onResume();if (mAccessoryConnection != null && mAccessoryConnection.isOpen()) {mAccessoryConnection.startReading();}}@Overridepublic void onPause() {super.onPause();if (mAccessoryConnection != null && mAccessoryConnection.isOpen()) {mAccessoryConnection.stopReading();}}@Overrideprotected void onDestroy() {super.onDestroy();unregisterReceiver(mUsbReceiver);if (mAccessoryConnection != null && mAccessoryConnection.isOpen()) {mAccessoryConnection.close();}}private final BroadcastReceiver mUsbReceiver = new BroadcastReceiver() {public void onReceive(Context context, Intent intent) {String action = intent.getAction();if (ACTION_USB_PERMISSION.equals(action)) {synchronized (this) {UsbAccessory accessory = (UsbAccessory) intent.getParcelableExtra(UsbManager.EXTRA_ACCESSORY);if (intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false)) {openAccessory(accessory);} else {Log.d(TAG, "permission denied for accessory " + accessory);}mPermissionRequestPending = false;}}}};private void openAccessory(UsbAccessory accessory) {mAccessoryConnection = new UsbAccessoryConnection(this, accessory);mAccessoryConnection.open();}private class UsbAccessoryConnection implements Runnable {private final UsbManager mUsbManager;private final UsbAccessory mAccessory;private UsbDeviceConnection mConnection;private UsbEndpoint mInEndpoint;private UsbEndpoint mOutEndpoint;private InputStream mInputStream;private OutputStream mOutputStream;private Thread mReadThread;private boolean mIsRunning;public UsbAccessoryConnection(Context context, UsbAccessory accessory) {mUsbManager = (UsbManager) context.getSystemService(Context.USB_SERVICE);mAccessory = accessory;}public void open() {mConnection = mUsbManager.openAccessory(mAccessory);if (mConnection != null) {mInEndpoint = mAccessory.getEndpoint(0);mOutEndpoint = mAccessory.getEndpoint(1);mInputStream = new BufferedInputStream(mConnection.openInputStream(mInEndpoint), MAX_PACKET_SIZE);mOutputStream =new BufferedOutputStream(mConnection.openOutputStream(mOutEndpoint), MAX_PACKET_SIZE);mIsRunning = true;mReadThread = new Thread(this);mReadThread.start();} else {Log.d(TAG, "openAccessory failed");}}public void close() {mIsRunning = false;if (mReadThread != null) {try {mReadThread.join();} catch (InterruptedException e) {e.printStackTrace();}}if (mInputStream != null) {try {mInputStream.close();} catch (IOException e) {e.printStackTrace();}}if (mOutputStream != null) {try {mOutputStream.close();} catch (IOException e) {e.printStackTrace();}}if (mConnection != null) {mConnection.close();}}public boolean isOpen() {return mConnection != null;}public void startReading() {if (mReadThread != null && !mReadThread.isAlive()) {mIsRunning = true;mReadThread = new Thread(this);mReadThread.start();}}public void stopReading() {mIsRunning = false;}public void write(byte[] data) {if (mOutputStream != null) {try {mOutputStream.write(data);mOutputStream.flush();} catch (IOException e) {e.printStackTrace();}}}@Overridepublic void run() {byte[] buffer = new byte[MAX_PACKET_SIZE];while (mIsRunning) {try {int len = mInputStream.read(buffer);if (len > 0) {final String receivedData = new String(buffer, 0, len);runOnUiThread(new Runnable() {@Overridepublic void run() {// 处理接收到的数据}});}} catch (IOException e) {e.printStackTrace();mIsRunning = false;}}}}

在上面的代码中，我们首先检查是否已连接 USB 配件。如果已连接，则尝试打开连接。如果没有权限，则请求权限。如果没有可用的 USB 配件，则在日志中记录错误消息。

在打开连接后，我们创建一个 UsbAccessoryConnection 对象，并使用 open() 方法打开连接。在 open() 方法中，我们获取连接的 UsbDeviceConnection 对象，并使用它来获取读取和写入数据的输入/输出流。我们还启动了一个读线程，该线程不断地从输入流中读取数据，并将其传递给主线程以进行处理。

最后，我们可以使用 write() 方法向 USB 主机发送数据，并使用 close() 方法关闭连接。

以上就是Android usb 配件模式下的示例，在实际的开发过程中会比较复杂，但原理基本类似。如果文档对你有帮助，欢迎点赞、收藏和评论，谢谢！