Question

我在页面上有一个滑块，显示音频的播放进度。然而，它并没有动。此外，它不能通过拖动移动，它始终保持在0.我使用滑块的PointerPressed和PointerReleased事件来做到这一点。

奇怪的是，如果我在slider上放置一个断点.Maximum = mediaPlayer.PlaybackSession.NaturalDuration.TotalSeconds;在PlayMedia方法中，在点击并恢复后，滑块工作正常!!!

以下是一些相关代码。

<Slider x:Name="slider" Width="Auto" Height="30" Margin="10,0,10,0" VerticalAlignment="Center" />


public sealed partial class MoreRuqya : Page
{
    private bool bMediaStop = false;
    private MediaPlayer mediaPlayer = new MediaPlayer();
    private int playIndex = 0;  //media index
    private DispatcherTimer timer = new DispatcherTimer();
    private DownloadFile _download = new DownloadFile();

    private void Page_Loaded(object sender, RoutedEventArgs e)
    {
        if (App.lstMoreRuqya == null)
        {
            App.lstMoreRuqya = DataLoader.LoadMoreRuqya();
        }

        var result = from rq in App.lstMoreRuqya group rq by rq.Category into grp orderby grp.Key select grp;

        cvsMoreRuqya.Source = result;

        mediaPlayer.MediaEnded += MediaPlayer_MediaEnded;
        mediaPlayer.BufferingStarted += MediaPlayer_BufferingStarted;
        mediaPlayer.BufferingEnded += MediaPlayer_BufferingEnded;

        //*************needed for PointerPressed & PointerReleased events to trigger**********************
        slider.AddHandler(PointerPressedEvent, new PointerEventHandler(Slider_PointerPressed), true);
        slider.AddHandler(PointerReleasedEvent, new PointerEventHandler(slider_PointerReleased), true);
        //************************************************************************************************

        _download.Status += _download_Status;

        if (mediaPlayer.PlaybackSession.PlaybackState == MediaPlaybackState.Playing)
        {
            Play.Symbol = Symbol.Pause;
        }
        else
        {
            Play.Symbol = Symbol.Play;
        }

        InitializeTimer();
    }

    private void MediaPlayer_BufferingStarted(MediaPlayer sender, object args)
    {
        lblMediaInfo.Text = "Buffering...";
    }

    private void MediaPlayer_BufferingEnded(MediaPlayer sender, object args)
    {
        slider.Maximum = mediaPlayer.PlaybackSession.NaturalDuration.TotalSeconds;
    }

    private void MediaPlayer_MediaEnded(MediaPlayer sender, object args)
    {
        PlayNext();
    }

    private void btnPlay_Click(object sender, RoutedEventArgs e)
    {
        //filter list for only selected items
        var selected = from rq in App.lstMoreRuqya where rq.isSelected == true select rq;
        App.lstSelectedMoreRuqya = selected.ToList();

        if (Play.Symbol.Equals(Symbol.Play))
        {
            if (mediaPlayer.PlaybackSession.PlaybackState == MediaPlaybackState.Paused & !bMediaStop)
            {
                mediaPlayer.Play();
            }
            else
            {
                bMediaStop = false;
                PlayMedia(playIndex);
            }

            Play.Symbol = Symbol.Pause;

            timer.Start();
        }
        else if (Play.Symbol.Equals(Symbol.Pause))
        {
            mediaPlayer.Pause();

            Play.Symbol = Symbol.Play;

            timer.Stop();
        }
    }

    private void PlayMedia(int index)
    {
        //if past last item in playlist & last item has been repeated
        if (index > App.lstSelectedMoreRuqya.Count || App.lstSelectedMoreRuqya.Count == 0)
        {
            Play.Symbol = Symbol.Play;

            return;
        }

        string uri = App.lstSelectedMoreRuqya[playIndex].urlPath;

        mediaPlayer.Source = MediaSource.CreateFromUri(new Uri(uri));
        mediaPlayer.AutoPlay = true;

        slider.Maximum = mediaPlayer.PlaybackSession.NaturalDuration.TotalSeconds;
    }

    private void timer_Tick(object sender, object e)
    {
        if (mediaPlayer.PlaybackSession.PlaybackState == MediaPlaybackState.None)
        {
            lblMediaInfo.Text = "";
        }

        if (mediaPlayer.PlaybackSession.PlaybackState == MediaPlaybackState.Playing)
        {
            slider.Value = Convert.ToDouble(mediaPlayer.PlaybackSession.Position.Seconds);
            lblMediaInfo.Text = App.lstSelectedMoreRuqya[playIndex].RuqyaName + " (" + FormatDuration(mediaPlayer.PlaybackSession.Position) + "/" + FormatDuration(mediaPlayer.PlaybackSession.NaturalDuration) + ")";
        }
    }

    private void InitializeTimer()
    {
        timer.Interval = TimeSpan.FromMilliseconds(1000);
        timer.Tick += timer_Tick;

        timer.Start();
    }

    private void Slider_PointerPressed(object sender, PointerRoutedEventArgs e)
    {
        timer.Stop();
    }

    private void slider_PointerReleased(object sender, PointerRoutedEventArgs e)
    {
        mediaPlayer.PlaybackSession.Position = TimeSpan.FromSeconds(slider.Value);
        timer.Start();
    }
}

Answer 1

此外，它无法通过拖动移动，它始终保持为0

由以下代码行

引起

slider.Maximum = mediaPlayer.PlaybackSession.NaturalDuration.TotalSeconds;

将滑块的最大值设置为0，这样就不能将滑块的值设置为大于0.您可以添加System.Diagnostics.Debug.WriteLine(slider.Maximum);来测试它。 NaturalDuration.TotalSeconds获得0结果的原因应该是PlaybackSession的MediaPlayer未完成打开。

解决此问题的更好方法是在源OpenOperationCompleted之后获得MediaSource的持续时间。例如：

private void PlayMedia(int index)
{ 
    MediaSource mediasource = MediaSource.CreateFromUri(new Uri("ms-appx:///Assets/test.mp3")); 
    mediasource.OpenOperationCompleted += Mediasource_OpenOperationCompleted;
    mediaPlayer.Source = mediasource;
    mediaPlayer.AutoPlay = true; 
    //slider.Maximum = mediaPlayer.PlaybackSession.NaturalDuration.Seconds;
    //System.Diagnostics.Debug.WriteLine(slider.Maximum);
} 

private async void Mediasource_OpenOperationCompleted(MediaSource sender, MediaSourceOpenOperationCompletedEventArgs args)
{       
    var _duration = sender.Duration.GetValueOrDefault();
    await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, () =>
    {           
        slider.Minimum = 0;
        slider.Maximum = _duration.TotalSeconds;
        slider.StepFrequency = 1;
    });
}

更多详情请参阅Use MediaTimelineController to synchronize content across multiple players。此部分包含滑块示例。

UWP滑块在播放期间不会移动

1 个答案: