Android SimpleOnPageChangeListener - Determine swipe direction

I have a class that extends SimpleOnPageChangeListener and in my onPageScrollStateChanged method I want to be able to determine whether the user has swiped forwards or backwards through the ViewPager. I.e. Whether they have swiped left-to-right or right-to-left.

I've done a lot of googling on this but I can't find anything about it. I was expecting the onPageScrollStateChanged method would provide a parameter stating which direction the swipe was but it doesn't.

    @Override
    public void onPageScrollStateChanged(int state) {

        // Determine whether the user is swiping forwards or backwards through the ViewPager
    }

Does anyone have any ideas?

Cheers Mike