我有一个滑块作为音轨时间线的轨迹栏。使用NAudion从网络播放音轨。所有代码均来自NAudio WPF示例。我仅更改了可访问性修饰符。第一次开始播放第一首曲目时一切正常，但是如果更改为下一首曲目，则滑块仍处于开始状态，并且仅在单击``暂停''后再进行播放。< / p>
要完全理解：
第一首曲目-滑块可以移动。
更改为下一首曲目-开头的滑块不动。但是先按“暂停”再按“播放”后，它开始移动。它会立即移至当前正在播放的位置并继续正常操作。接下来的每个曲目都是如此。
PlayerUserControl的VM代码：
public class AudioControlVM : ViewModelBase, IDisposable
{
private AudioModel _currentSong;
public AudioModel CurrentSong { get { return _currentSong; } set { _currentSong = value; RaisePropertyChanged("CurrentSong"); } }
private string inputPath, songName;
private string defaultDecompressionFormat;
public IWavePlayer wavePlayer { get; set; }
private WaveStream reader;
public RelayCommand PlayCommand { get; set; }
public RelayCommand PauseCommand { get; set; }
public RelayCommand StopCommand { get; set; }
public DispatcherTimer timer = new DispatcherTimer();
private double sliderPosition;
private readonly ObservableCollection<string> inputPathHistory;
private string lastPlayed;
public AudioControlVM()
{
inputPathHistory = new ObservableCollection<string>();
PlayCommand = new RelayCommand(() => Play());
PauseCommand = new RelayCommand(() => Pause());
StopCommand = new RelayCommand(Stop, () => !IsStopped);
timer.Interval = TimeSpan.FromMilliseconds(500);
timer.Tick += TimerOnTick;
}
public bool IsPlaying => wavePlayer != null && wavePlayer.PlaybackState == PlaybackState.Playing;
public bool IsStopped => wavePlayer == null || wavePlayer.PlaybackState == PlaybackState.Stopped;
public IEnumerable<string> InputPathHistory => inputPathHistory;
const double SliderMax = 10.0;
private void TimerOnTick(object sender, EventArgs eventArgs)
{
if (reader != null)
{
sliderPosition = reader.Position * SliderMax / reader.Length;
RaisePropertyChanged("SliderPosition");
}
}
public double SliderPosition
{
get => sliderPosition;
set
{
if (sliderPosition != value)
{
sliderPosition = value;
if (reader != null)
{
var pos = (long)(reader.Length * sliderPosition / SliderMax);
reader.Position = pos; // media foundation will worry about block align for us
}
RaisePropertyChanged("SliderPosition");
}
}
}
private bool TryOpenInputFile(string file)
{
bool isValid = false;
try
{
using (var tempReader = new MediaFoundationReader(file))
{
DefaultDecompressionFormat = tempReader.WaveFormat.ToString();
InputPath = file;
isValid = true;
}
}
catch (Exception e)
{
}
return isValid;
}
public string DefaultDecompressionFormat
{
get => defaultDecompressionFormat;
set
{
defaultDecompressionFormat = value;
RaisePropertyChanged("DefaultDecompressionFormat");
}
}
public string SongName { get => songName; set
{
songName = value;
RaisePropertyChanged("SongName");
} }
public string InputPath
{
get => inputPath;
set
{
if (inputPath != value)
{
inputPath = value;
AddToHistory(value);
RaisePropertyChanged("InputPath");
}
}
}
private void AddToHistory(string value)
{
if (!inputPathHistory.Contains(value))
{
inputPathHistory.Add(value);
}
}
public void Stop()
{
if (wavePlayer != null)
{
wavePlayer.Stop();
}
}
public void Pause()
{
if (wavePlayer != null)
{
wavePlayer.Pause();
RaisePropertyChanged("IsPlaying");
RaisePropertyChanged("IsStopped");
}
}
public void Play()
{
if (String.IsNullOrEmpty(InputPath))
{
return;
}
if (wavePlayer == null)
{
CreatePlayer();
}
if (lastPlayed != inputPath && reader != null)
{
reader.Dispose();
reader = null;
}
if (reader == null)
{
reader = new MediaFoundationReader(inputPath);
lastPlayed = inputPath;
wavePlayer.Init(reader);
}
wavePlayer.Play();
RaisePropertyChanged("IsPlaying");
RaisePropertyChanged("IsStopped");
timer.Start();
}
private void CreatePlayer()
{
wavePlayer = new WaveOutEvent();
wavePlayer.PlaybackStopped += WavePlayerOnPlaybackStopped;
RaisePropertyChanged("wavePlayer");
}
private void WavePlayerOnPlaybackStopped(object sender, StoppedEventArgs stoppedEventArgs)
{
if (reader != null)
{
SliderPosition = 0;
//reader.Position = 0;
timer.Stop();
}
if (stoppedEventArgs.Exception != null)
{
}
RaisePropertyChanged("IsPlaying");
RaisePropertyChanged("IsStopped");
}
public void PlayFromUrl(string url, string songname)
{
Stop();
inputPath = url;
SongName = songname;
Play();
}
public void Dispose()
{
wavePlayer?.Dispose();
reader?.Dispose();
}
}
播放器的XAML：
<Grid>
<StackPanel Orientation="Horizontal">
<Button Content="Play" Command="{Binding PlayCommand}" VerticalAlignment="Center" Width="75" />
<Button Content="Pause" Command="{Binding PauseCommand}" VerticalAlignment="Center" Width="75" />
<Button Content="Stop" Command="{Binding PlayCommand}" VerticalAlignment="Center" Width="75" />
<Slider VerticalAlignment="Center" Value="{Binding SliderPosition, Mode=TwoWay}" Maximum="10" Width="400" />
<TextBlock Text="{Binding SongName, FallbackValue=Test}" Foreground="White"/>
</StackPanel>
</Grid>
</UserControl>
用于发送新曲目数据的VM代码：
public class AudioModel
{
public string Artist { get; set; }
public string SongName { get; set; }
public int Duration { get; set; }
public string URL { get; set; }
public RelayCommand PlayThisAudioCommand
{
get;
private set;
}
public AudioModel()
{
PlayThisAudioCommand = new RelayCommand(() => PlayThis());
}
private void PlayThis()
{
if (URL != null)
{
TestVM.AudioConrol.PlayFromUrl(URL, SongName);
}
else;
}
}
答案 0 :(得分：2)
您的计时器似乎有一个多线程问题。事件的顺序似乎是：
这里的重点是Play（）和WavePlayerOnPlaybackStopped（）的调用顺序。事件很可能按上述顺序发生-waveWlayer在另一个线程上引发PlaybackStopped事件。
简而言之-WavePlayerOnPlaybackStopped（）正在停止您的计时器 Play（）启动后，这就是为什么您的滑块没有更新。按“暂停”，然后按“播放”将重新启动计时器，这就是滑块在暂停后开始更新的原因。
您可以通过暂时注释WavePlayerOnPlaybackStopped（）中的代码进行测试，这应该可以解决此问题-尽管当轨道到达终点或停止时滑块不会重置为零。
注意：调用wavePlayer.Stop（）和wavePlayer.PlaybackStopped事件之间出现延迟的原因是由于nAudio使用专用线程来处理回放。当您调用Stop（）时，它必须在实际停止之前完成对当前音频缓冲区的处理-这在大多数情况下会导致几毫秒的延迟。
您可以在WaveOutEvent的DoPlayback方法中看到这一点：https://github.com/naudio/NAudio/blob/master/NAudio/Wave/WaveOutputs/WaveOutEvent.cs#L147