The COVID-19 does not survive by itself. Without the host cell, it will gradually inactivated. The survival time of COVID-19 is currently considered to be approximately 6-9 days near to normal environment on inanimate surfaces without any disinfection.
But actually, there are two problems to think about:
First, the positive result of viral nucleic acids does not suggest that the COVID-19 virus is still active.
Nucleic acid is method to determine the presence of viruses in the environment in most situations. But the nucleic acid is only a part of the virus body, positive result does not mean that the virus is still alive, it may also means the presence of the leaving part of the nucleic acid of dead virus.
Most of the environment detection, suggesting that such surface virus is positive, it doesn’t means that the live COVID-19 virus is existed.
Second, Survival time will change in different environmental conditions.
The lower the temperature, the more constant temperature and humidity, the less sunlight and the smoother the surface of the object, the longer the survival time of COVID-19 virus.
Among all the factors that affect the COVID-19 survival time, sunlight may be the most critical factors. Experiments have also suggested that under conditions that mimic sunlight, any level of sunlight can massively inactivate viruses on surfaces just in minutes.
In shorts, COVID-19 transmission is generally carried by droplets and contact, so take precautions to avoid going out and contact as much as possible.