Huawei nova9 A9 A9 turns on the black screen of the video front camera.

Restart or start misoperation prevention.

Try to restart the phone first, but restarting the phone won't solve it. Open the settings, and click accessibility. Set here to turn off the misoperation prevention mode. Preventing accidental touch depends on the proximity sensor above the mobile phone. The emitting part of the sensor will emit pulsed light. When there is no obstacle at close range, the light will not be reflected, so there is no signal at the receiving part. At this time, the touch screen of the mobile phone works normally.