As unanswered in Various issues while attempting to show custom metadata on map / hook gestures in ArcGIS Runtime SDK...
OnZoomListener.postAction does not fire reliably at the end of a series of zoom actions, particularly if zoom is triggered during an existing zoom animation.
Is there intention to add reliable events for zoom/pan which consistently fire when zoom/pan is actioned and completes, no matter whether the action is triggered programatically, by normal user interaction, or by extended handling of gestures?