startRemoteView method Null safety
Display remote video image or substream
Parameters:
userId   userId of the specified remote user
streamType Video stream type of the userId specified for watching:
- 
HD big image: TRTCCloudDef.TRTC_VIDEO_STREAM_TYPE_BIG 
- 
Smooth big image: TRTCCloudDef.TRTC_VIDEO_STREAM_TYPE_SMALL 
- 
Substream (screen sharing): TRTCCloudDe.TRTC_VIDEO_STREAM_TYPE_SUB 
viewId   viewId generated by TRTCCloudVideoView
Implementation
Future<void> startRemoteView(
    String userId, // User ID
    int streamType,
    int viewId) {
  return TRTCCloudVideoViewController(viewId)
      .startRemoteView(userId, streamType);
}