意图筛选器不为onReceive调用USB_ACCESSORY_ATTACHED

Question

我在USB_ACCESSORY_ATTACHED的构造函数中声明了MyDialogFragment的意图过滤器，并在片段的onResume和onPause方法中注册/注销了它。MyReceiver在内部类中扩展BroadcastReceiver以接收USB_ACCESSORY_ATTACHED意图。见以下代码：

public class MyDialogFragment extends DialogFragment {

     private Context context;
     private IntentFilter usbIntentFilter;
     private MyReceiver myReceiver;

     MyDialogFragment(Context context) {
        usbIntentFilter = new IntentFilter(UsbManager.ACTION_USB_ACCESSORY_ATTACHED);
        myReceiver = new myReceiver();
        this.context = context;
     }


     @Override
     public void onResume() {
          super.onResume();

          // Register broadcast receiver
         context.registerReceiver(myReceiver, usbIntentFilter);
     }

     @Override
     public void onPause() {
          super.onPause();

          // Unregister broadcast receiver
          context.unregisterReceiver(myReceiver);
     }

     class MyReceiver extends BroadcastReceiver {

        @Override
        public void onReceive(Context context, Intent intent) {

            Log.d("MyApp","Called USB receiver");

        }
     }
}

但是，当我附加一个onReceive附件时，MyReceiver的MyReceiver方法就不会被调用。此外，当我改变意图时

usbIntentFilter = new IntentFilter(UsbManager.ACTION_USB_ACCESSORY_DETACHED);

onReceive方法MyReceiver确实会被调用。所以我的问题是:为什么当我分离附件的时候，它会工作，而当我附加附件的时候，它却不起作用？

Answer 1

因此，USB_ACESSORY_ATTACHED意图似乎从未真正深入到该活动中，请参见这样的问题：

ATTACHED

您必须使用由onResume间接调用的USB_ACCESSORY_ATTACHED方法。我不得不说，这在Android文档中是不清楚的，我怀疑它的实现。