Android: Setting ListView fast scroll based on visible positions

Question

I am trying to set the fast scroll enabled and visible if there are more items in the list than are currently visible. After setting the adapter, the ListView's count is properly increased but the last visible position is not. As a result I am currently posting a Runnable to wait until the ListView has figured out what items are / aren't visible. The code is as follows:

listView.post(new Runnable(){
    @Override
    public void run() {
        if(listView.getLastVisiblePosition() < (listView.getCount() - 1)){
            listView.setFastScrollAlwaysVisible(true);
            listView.setFastScrollEnabled(true);
        }
    }
});

This solution works fine, but feels a bit hackish. Is there a way to know when the last visible position is updated without posting the runnable? Thanks in advance!