我正在使用这个库和函数来读取和显示来自 excel 部件的列和行。阅读和显示部分似乎工作正常。但是，在 StreamBuilder<MediaState>(
stream: _mediaStateStream,
builder: (context, snapshot) {
final mediaState = snapshot.data;
return ProgressBar(
total:
mediaState?.mediaItem?.duration ?? Duration.zero,
progress: mediaState?.position ?? Duration.zero,
buffered: mediaState?.playbackState?
.bufferedPosition ?? Duration.zero,
onSeek: (newPosition) {
AudioService.seekTo(newPosition);
},
);
},
),
...
Stream<MediaState> get _mediaStateStream =>
Rx.combineLatest3<MediaItem, Duration, PlaybackState, MediaState>(
AudioService.currentMediaItemStream,
AudioService.positionStream,
AudioService.playbackStateStream,
(mediaItem, position, playbackState) =>
MediaState(mediaItem, position, playbackState));
...
class MediaState {
final MediaItem mediaItem;
final Duration position;
final PlaybackState playbackState;
MediaState(this.mediaItem, this.position, this.playbackState);
}
语句中，当我设置 else 并尝试稍后打印时，它给了我 setCols
undefined为什么会这样？
console.log('what are the cols', cols)