What is safe to put in OnCreateOptionsMenu in Android Activity?

Question

In my app I have a Spinner as a menu item in the action bar of my Activity. It has the collapsible action view so it appears only when the icon is clicked. I obtain a reference to my Spinner like this:

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.my_menu, menu);
    spinner = (Spinner)menu.findItem(R.id.spinner).getActionView();
    spinner.setAdapter(spinnerAdapter);
    return true;
}

I have been reading about when OnCreateOptionsMenu is called and answers vary, with some saying it's called during onCreate. The problem is the spinnerAdapter is initialized in onCreate, and more importantly, the ArrayList containing the data for the Spinner is initialized and populated from a Room database in onCreate. So my question is, is it possible that the code from OnCreateOptionsMenu gets executed before some of the code in onCreate?