Android USB 通信开发
Android USB 通信开发主要涉及两种模式:主机模式(Host Mode)和配件模式(Accessory Mode)。以下是开发USB通信应用的关键知识点和步骤。
1. 基本概念
主机模式(Host Mode)
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Android设备作为USB主机,控制连接的USB设备
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需要设备支持USB主机功能(通常需要OTG支持)
配件模式(Accessory Mode)
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Android设备作为USB配件被其他主机控制
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需要设备支持USB配件模式
2. 开发准备
清单文件配置
<!-- 声明USB主机功能 -->
<uses-feature android:name="android.hardware.usb.host" /><!-- 声明USB配件功能(如果需要) -->
<uses-feature android:name="android.hardware.usb.accessory" /><!-- 添加必要的权限 -->
<uses-permission android:name="android.permission.USB_PERMISSION" />
3. USB主机模式开发
发现连接的USB设备
UsbManager usbManager = (UsbManager) getSystemService(Context.USB_SERVICE);
HashMap<String, UsbDevice> deviceList = usbManager.getDeviceList();
请求设备权限
private static final String ACTION_USB_PERMISSION = "com.example.USB_PERMISSION";PendingIntent permissionIntent = PendingIntent.getBroadcast(this, 0, new Intent(ACTION_USB_PERMISSION), PendingIntent.FLAG_IMMUTABLE);IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);
registerReceiver(usbReceiver, filter);usbManager.requestPermission(device, permissionIntent);
广播接收器处理权限结果
private final BroadcastReceiver usbReceiver = new BroadcastReceiver() {public void onReceive(Context context, Intent intent) {String action = intent.getAction();if (ACTION_USB_PERMISSION.equals(action)) {synchronized (this) {UsbDevice device = intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);if (intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false)) {if(device != null){// 权限已授予,可以通信openDevice(device);}} else {Log.d(TAG, "权限被拒绝 for device " + device);}}}}
};
打开设备并通信
private void openDevice(UsbDevice device) {UsbInterface intf = device.getInterface(0);UsbEndpoint endpoint = intf.getEndpoint(0);UsbDeviceConnection connection = usbManager.openDevice(device);if (connection == null) return;connection.claimInterface(intf, true);// 发送数据byte[] sendData = "Hello".getBytes();int sent = connection.bulkTransfer(endpoint, sendData, sendData.length, 0);// 接收数据byte[] receiveData = new byte[64];int received = connection.bulkTransfer(endpoint, receiveData, receiveData.length, 0);
}
4. USB配件模式开发
清单文件配置
<activity ...><intent-filter><action android:name="android.hardware.usb.action.USB_ACCESSORY_ATTACHED" /></intent-filter><meta-data android:name="android.hardware.usb.action.USB_ACCESSORY_ATTACHED"android:resource="@xml/accessory_filter" />
</activity>
配件过滤器(xml/accessory_filter.xml)
<resources><usb-accessory manufacturer="YourCompany" model="YourModel" version="1.0" />
</resources>
检测配件连接
UsbManager usbManager = (UsbManager) getSystemService(Context.USB_SERVICE);
UsbAccessory[] accessoryList = usbManager.getAccessoryList();if (accessoryList != null && accessoryList.length > 0) {UsbAccessory accessory = accessoryList[0];openAccessory(accessory);
}
打开配件通信
private void openAccessory(UsbAccessory accessory) {ParcelFileDescriptor fd = usbManager.openAccessory(accessory);if (fd != null) {FileDescriptor fileDescriptor = fd.getFileDescriptor();FileInputStream inputStream = new FileInputStream(fileDescriptor);FileOutputStream outputStream = new FileOutputStream(fileDescriptor);// 现在可以通过输入输出流进行通信}
}
5. 常见问题
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权限问题:确保正确请求和处理USB权限
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设备兼容性:并非所有Android设备都支持USB主机模式
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线程阻塞:USB通信可能阻塞UI线程,建议在后台线程进行
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连接稳定性:处理USB设备插拔事件
6. 高级主题
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USB串口通信:使用CDC(Communication Device Class)协议
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HID设备通信:与键盘、鼠标等HID设备交互
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同步通信:使用控制传输(Control Transfer)和中断传输(Interrupt Transfer)
7. 推荐库
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usb-serial-for-android:简化USB串口通信
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libusb-android:提供更底层的USB访问
开发时请参考Android官方USB文档获取最新信息。