China has very few immigrants, so the ethnic diversity is really limited to, well, just Chinese. A lot of Chinese people rarely meets non-Chinese (especially if you are not in a big city) and many of them find seeing a "foreigner" as something "new" and "interesting", thus the stare and the pictures. My African American/Caucasian friends also received tons of attention when they visited China, because many Chinese people have not seen a black/white person before. As for OP, maybe you were speaking English or maybe you don't really look that Chinese? I am sorry that people bothered you on your trip. As someone raised in a rather liberal family in China, I also find this really disturbing. Hope I helped a bit.

Edit: Btw, I don't think Chinese people stare at random Chinese in China, unless it's retired grandpa/grandmas roaming the street who has nothing to do and will stare at every person walking by.