EventBusException: its super classes have no public methods with the @Subscribe annotation

Question

I am working on the ROS android project. I am implementing the EventBus to constantly updating the value for textViews. I am posting values from ManActivity to MainFragment

But I am getting below Error

org.greenrobot.eventbus.EventBusException: Subscriber class com.korechi.roamioapp.MainActivity and its super classes have no public methods with the @Subscribe annotation

I tried this link but it didn't help. And I am not using the proGuard so I don't think I need any rule to fix and not sure how proGuard works.

Thank you, any help much appreciated.

I am registering Event on MainActivity and my MainActivity extends AppCompatRosActivity

  @Override
protected void onStart() {
    super.onStart();
    EventBus.getDefault().register(this);
}

@Override
protected void onStop() {
    super.onStop();
    EventBus.getDefault().unregister(this);
}

Posting the value from MainActivity

     Subscriber<Float32> speed = connectedNode.newSubscriber("/RoamIO/speed/app_ver", Float32._TYPE);
        speed.addMessageListener(new MessageListener<Float32>() {
            @SuppressLint("StringFormatMatches")
            @Override
            public void onNewMessage(Float32 float32) {

                Log.d(TAG, "onNewMessage: /RoamIO/speed/app_ver : "+String.format(getResources().getString(R.string.speedMetric)));
                fragmentMessages.setSpeed(String.format(getResources().getString(R.string.speedMetric)));
                EventBus.getDefault().post(fragmentMessages);
//                mainFragment.speedTxtView.setText(String.format(getResources().getString(R.string.speedMetric),
//                        float32.getData()));
            }
        });

subscribing from MainFragment like this

@Subscribe(threadMode = ThreadMode.MAIN)
    public void onEvent(Messages messages){
       speedTxtView.setText(messages.getSpeed());
    }

Gradle

implementation 'org.greenrobot:eventbus:3.2.0'