Whatsapp 如何在 Android 11 上获得 SYSTEM_ALERT_WINDOW 权限？

Question

When a Whatsapp call is recieved, the phone wakes up in lock screen and starts ringing. As per this article, I understand that now the user has to explicitly go and give the "Display Over Other Apps" permission from the settings, so that Whatsapp can perform this. Given that the user doesn't have to do it in any of the stages of WhatsApp's first installation, how do they achieve this? Do they have access to some internal permissions, or is there more at play here?

Answer 1

For incoming calls & alarms, apps typically post a high priority notification and specify a fullscreen intent - which may be launched by the system (eg. when the screen is off):

https://developer.android.com/training/notify-user/time-sensitive

Such apps (including WhatsApp) do not use the SYSTEM_ALERT_WINDOW permission for this purpose.