getActiveNotifications
Recover a list of active notifications: ones that have been posted by the calling app that have not yet been dismissed by the user or canceled by the app.
StatusBarNotification object, including the original and supplied to (via and ) as well as a copy of the original object (via ).
From Q, will also return notifications you've posted as an app's notification delegate via notifyAsPackage.
Returns an empty list on LOLLIPOP_MR1 and earlier.
Return
A list of StatusBarNotification.