You can apply for a China Travel Visa(https://www.travelchinaguide.com/embassy/visa/tourist.htm) from Chinese embassy in Sri lanka. Take along with you your valid passport with blank pages, one recent passport-sized photo, one application form, travel information including the booking of airline ticket and itinerary in China. Possibly, you will need an invitation letter from your friend.

You need a visa notification letter and your friend cannot apply for it. It has to be registered company in China who needs to apply for the visa notification letter. If you do not have a Chinese company to sponsor you then you cannot get a visa to China.