Called to let you know that the specified picker is now receiving input from the Digital Crown.
- watchOS 2.0+
A picker becomes focused when the user taps it or when you call the
focus method of the picker itself. When a picker is focused, input from the Digital Crown updates the selected item.
The default implementation of this method does nothing. Subclasses can override it and use it to perform actions related to the picker receiving focus. You do not need to call
super in your implementation.