1. The current mobile phones all support the distance sensor function. When the distance sensor above the screen is blocked during a call, if it is placed near the ear, the screen will close, which is normal;
2. The distance sensor is not set correctly, resulting in a black screen. It is recommended to go to the mobile phone [Settings] - [Display] - [Sensor Verification] to verify again;
3. Power saving function of mobile phone. There is a light sensing system in front of the mobile phone. When making a call, the mobile phone is close to the head. The light sensing system detects that the light is dim, so it saves power on the black screen. The mobile phone leaves the head and the screen recovers;
4. When the distance sensor fails, it is not possible to correctly judge whether there is an object approaching, which may lead to a false judgment that there is no object approaching when making a call, and then close the mobile phone screen. Therefore, it is recommended that the mobile phone be sent to the official designated maintenance center for maintenance.