怎么在Android中利用广播对usb连接状态进行监听

package com.lgs.test.testcode.receiver; import android.content.BroadcastReceiver; import android.content.Context; import android.content.Intent; import android.content.IntentFilter; import android.widget.Toast;  public class UsbConnect {   private final static String ACTION = "android.hardware.usb.action.USB_STATE";   public void start(Context context) {     IntentFilter filter = new IntentFilter();     filter.addAction(ACTION);     context.registerReceiver(usBroadcastReceiver, filter);   }   BroadcastReceiver usBroadcastReceiver = new BroadcastReceiver() {     @Override     public void onReceive(Context context, Intent intent) {       String action = intent.getAction();       Toast.makeText(context, "aciton =" + action, Toast.LENGTH_SHORT).show();       if (action.equals(ACTION)) {         boolean connected = intent.getExtras().getBoolean("connected");         Toast.makeText(context, "aciton =" + connected, Toast.LENGTH_SHORT).show();         if (connected) {         } else {         }       }     }   }; }