To save power and for an optimal user experience, the system automatically changes the screen brightness in some scenarios.For example, when scanning a QR code in Alipay, the screen brightness increases instantly.
This is because the system brightness adjustment permission is open to third-party apps such as video, reader, and payment apps. (The screen brightness will decrease if the ambient light sensor is covered.) If you want the screen brightness to stay the same, open Settings, search for and touch Display & brightness/ Brightness, disable Automatic, then adjust the screen brightness to the desired level manually.
The screen brightness changes when the user opens, uses, or closes an app
