Chinese Culture Tip #1: Rubbing your leg with one hand is akin to a pat on the back and having someone sit next to you in a restaurant, legs touching despite there being an empty booth across the table means nothing other than "hey, you’re alright. I’m comfortable around you". Friendliness is inversely proportionate to the amount of personal space you’re given. Expect a random shoulder massage if they really like you, though it still has nothing to do with physical attraction.
Takes some getting used to, but I actually like it quite a bit. Fewer social barriers are never a bad thing! (or at least, not knowing about some of them – ignorance is bliss!)