@Override
protected void onResume() {
    super.onResume();
    IntentFilter intentFilter=new IntentFilter();
    intentFilter.addAction("com.huperly.test.FORCE_OFFLINE");
    receiver=new ForceOffLineReceiver();
    registerReceiver(receiver,intentFilter);
}

@Override
protected void onPause() {
    super.onPause();
    if (receiver!=null){
        unregisterReceiver(receiver);
        receiver=null;
    }
}

也试过onCreate+onDestroy的组合，仍出现了Receiver not registered: null错误