@Override
	public void instantiate() {
		if (mFactory == null) {
			throw new IllegalStateException("ViewFactory can't be null!");
		}
		super.instantiate();
	}
Usage: call {@link setFactory(ViewFactory)} then call {@link instantiate()}

@author A.Zaitsev
app/src/main/java/pro/alexzaitsev/freepager/library/view/infinite/InfiniteVerticalPager.java