可能是由于USB权限的问题,您需要在AndroidManifest.xml文件中添加特定的权限,并在代码中请求USB权限。 以下是解决方案的示例代码:
在AndroidManifest.xml文件中添加以下权限:
...
在您的Java代码中,请求USB权限,如下所示:
private static final String ACTION_USB_PERMISSION = "com.example.USB_PERMISSION";
BroadcastReceiver mUsbReceiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if (ACTION_USB_PERMISSION.equals(action)) {
synchronized (this) {
UsbDevice device = (UsbDevice)intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
if (intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false)) {
if(device != null){
// 现在你有了USB设备的访问权限,你可以做你需要的事
}
}
else {
Log.d(TAG, "permission denied for device " + device);
}
}
}
}
};
private void requestUsbPermission() {
UsbManager manager = (UsbManager) getSystemService(Context.USB_SERVICE);
PendingIntent pi = PendingIntent.getBroadcast(this, 0, new Intent(ACTION_USB_PERMISSION), 0);
IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);
registerReceiver(mUsbReceiver, filter);
manager.requestPermission(mUsbDevice, pi);
}
通过这种方式,您可以向用户请求USB权限,并在得到了授权后访问USB设备。