Android : How to set start page in PagerAdapter and swipe to next/previous page?

I have two activity. first activity have a list and second activity shows contents which is related to the chosen item of the list. I have created a subclass of PagerAdapter in order to change contents of second activity by swiping needless to back to first activity and select next item. (exactly same as turning page). but the problem is when I select an item, second activity starts from beginning! and when I set setCurrentItem() method in instantiateItem() method in order to provide corresponded item, it works, but I can't swipe the page and change the text! Anyway, I want to open a book from its middle and flip normally! :) How can I eliminate these problems? tnx!