It is thought that the main transmission method of Coronavirus is through saliva or tiny airborne droplets released from a cough or sneeze. If an infected particle finds its way to a hard surface such as the glass screen of your smartphone, it can remain there for up to 72 hours but will degrade and become less contagious as time passes.
This means that it is possible, though fairly unlikely that you will catch coronavirus from your phone directly, especially if you are practising physical distancing.
However, as we are still counting new cases and waiting on a vaccine, all preventative measures should be taken. This includes continued good personal hygiene practices which should extend to your phone, particularly because it is used so much. This includes cleaning (which we explain in the next section) and behavioural precautions that include not sharing your phone with others and keeping it stowed away as much as possible in public.