参数类型"Stream<SequenceState？>"不能分配给参数类型'Stream<SequenceState>?'

Question

我想提出一个音频播放器使用flutter然而_audioPlayer.sequenceStateStream给上面的错误。如何解决此错误?

代码:

final AudioPlayer _audioPlayer;
@override
Widget build(BuildContext context) {
return Row(
mainAxisSize: MainAxisSize.min,
children: [
StreamBuilder<bool>(
stream: _audioPlayer.shuffleModeEnabledStream,
builder: (context, snapshot) {
return _shuffleButton(context, snapshot.data ?? false);
},
),
StreamBuilder<SequenceState>(
stream: _audioPlayer.sequenceStateStream,
builder: (_, __) {
return _previousButton();
},
),

Answer 1

尝试在SequenceState后添加?:

final AudioPlayer _audioPlayer;
@override
Widget build(BuildContext context) {
return Row(
mainAxisSize: MainAxisSize.min,
children: [
StreamBuilder<bool>(
stream: _audioPlayer.shuffleModeEnabledStream,
builder: (context, snapshot) {
return _shuffleButton(context, snapshot.data ?? false);
},
),
StreamBuilder<SequenceState?>(
stream: _audioPlayer.sequenceStateStream,
builder: (_, __) {
return _previousButton();
},
),