public void scrollDown() {
		if (mNextPage == INVALID_SCREEN && mCurrentPage < getChildCount() - 1
				&& mScroller.isFinished()) {
			snapToPage(mCurrentPage + 1);
		}
	}
Snap pager to the specified page.

@param whichPage
           Zero based index of the page.
@param duration
           Duration in milliseconds of scrolling to the chosen page.
app/src/main/java/pro/alexzaitsev/freepager/library/view/core/VerticalPager.java