While still not the norm, I would say there are PLENTY of Chinese people who wear shorts in the summer, far more so than in many Asian countries. However, at night, if I was going to a reasonably upscale place (mid-level by western standards and up) I would most probably put on a pair of pants.

For the most part, shorts are just fine.

Let me rephrase: shorts might be acceptable to the restaurants but do you really want to sit down in shorts and polo shirt, with flipflops. Would you do the same at home?