PLAYER_PRELOAD_EVENT
Events that occur when media resources are preloaded.
Enumerator
- PLAYER_PRELOAD_EVENT_BEGIN
 - 0: Starts preloading media resources.
 - PLAYER_PRELOAD_EVENT_COMPLETE
 - 1: Preloading media resources is complete.
 - PLAYER_PRELOAD_EVENT_ERROR
 - 2: An error occurs when preloading media resources.