There are numerous social crackdown movements in China for the important conferences, big events, 6.4, hard attack, attacking prostitution. Each movements, gay people become victims of the politics. People are often talking about private act and public act. If law doesn't attack private sex act, people will think that gay will have more space. But in China, people especially gay people, don't have enough space for private act.
Some heterosexual couple have sex in the public in Shanghai before in know.
No special definition about sex in public. It means sexual minorities in the public or sex in public, it is not clear. Many of the times, police catch gay people just according to who is walking on the gay communicatin areas, such as parks or gardens. The Chinese criminal law system was different from the West. But the law will be changed this year.