SYSTEM_ALERT_WINDOW PERMISSION on API 26 not working as expected. Permission denied for window type 2002

Question

I am using overlay permission to display certain information in my app. Running it on API 23 - 25 it works fine (asking for permission, granting, etc. according to

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Answer 1

According to the documentation on Android 8.0 Behavior Changes for apps targeting Android 8.0:

Apps that use the SYSTEM_ALERT_WINDOW permission can no longer use the following window types to display alert windows above other apps and system windows:

TYPE_PHONE
TYPE_PRIORITY_PHONE
TYPE_SYSTEM_ALERT
TYPE_SYSTEM_OVERLAY
TYPE_SYSTEM_ERROR

Instead, apps must use a new window type called TYPE_APPLICATION_OVERLAY.

So your app could target some lower version. In this case, your alert window will ...

always appear beneath the windows that use the TYPE_APPLICATION_OVERLAY window type. If an app targets Android 8.0 (API level 26), the app uses the TYPE_APPLICATION_OVERLAY window type to display alert windows.

(quoted from the same source)