Why does Huawei p9 feel vibrating when the screen is closed?

In Huawei p9, you can turn off the sound and vibration while your mobile phone is waiting for a new message reminder from WeChat. The specific steps are: 1, open WeChat and log in; 2. Find the settings and select a new message reminder; 3. You can modify whether to open new message notification. If it is turned on, you can choose the way to turn it on, such as sound, prompt sound and vibration, and turn it off if you don't want any sound or vibration.