This property will return null if the map's Map.Animation contains no keyframes. Similar to how the map defines the layers that make up the map, the map defines the animation and the keyframes for all views of the map. However, it is possible to have multiple views of a map set to different times in the animation. This property returns an object can be used to set the current time or frame, step to the next or previous keyframe, or play and stop the animation.

Reference

MapView Class
MapView Members