NERtcLiveStreamVideoScaleMode constructor Null safety

1. yunxin_roomkit
2. roomkit
3. NERtcLiveStreamVideoScaleMode
4. NERtcLiveStreamVideoScaleMode constructor

NERtcLiveStreamVideoScaleMode class

1. Constructors
2. NERtcLiveStreamVideoScaleMode
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. noSuchMethod
8. toString
9. Operators
10. operator ==
11. Constants
12. liveStreamModeVideoScaleCropFill
13. liveStreamModeVideoScaleFit