NERtcVideoDeviceState constructor Null safety

1. nertc
2. nertc
3. NERtcVideoDeviceState
4. NERtcVideoDeviceState constructor

NERtcVideoDeviceState class

1. Constructors
2. NERtcVideoDeviceState
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. noSuchMethod
8. toString
9. Operators
10. operator ==
11. Constants
12. closed
13. disconnected
14. freezed
15. initialized
16. opened
17. unInitialized
18. unknownError