c# - 如何在 Windows8 中使用 MediaElement 更改视频的位置？

Question

目前我正在我的代码中执行此操作，

 playbackElement1.AutoPlay = true;
 playbackElement1.SetSource(stream, this.m_recordStorageFile.FileType);
 playbackElement1.Position = new TimeSpan(0, 0, 0, 0, 5000);
 playbackElement1.Play();

它不起作用，检查超过 5 秒的视频。

Answer 1

有两个问题。首先，MediaElement只能在媒体加载后设置位置，通过处理MediaOpened事件来确定。其次，并非所有媒体都是可搜索的。通过调用CanSeek进行检查。使用类似的东西：

playbackElement1.AutoPlay = true;
// Will fire after the media has loaded
playbackElement1.MediaOpened += (source, args) =>
{
    MediaElement player = (MediaElement) source;
    if (player.CanSeek)
    {
        player.Position = new TimeSpan(0, 0, 0, 0, 5000);   
    }
}                     
playbackElement1.SetSource(stream, this.m_recordStorageFile.FileType);

加载后，使用NaturalDuration属性查看媒体的长度，如果需要，使用HasTimeSpan和TimeSpan属性将其转换为 TimeSpan。

Answer 2

简而言之，您需要在 MediaElement 下方添加一个 Slider，就像在任何视频播放器中一样... - Slider 将更新播放器当前位置 - Timer 将每 300 毫秒更新一次滑块与当前播放器位置

代码：

<Slider x:Name="videoSlider" Thumb.DragStarted="videoSlider_DragStarted" Thumb.DragCompleted="videoSlider_DragCompleted" Margin="10,0,10,30" Height="18" VerticalAlignment="Bottom"/>

<MediaElement x:Name="videoPlayer" Margin="4,59,152,53" Volume=".5" MediaOpened="videoPlayer_MediaOpened"> 

[这是带有滑块的媒体元素的图片][1]

现在我们有了一个媒体元素和一个滑块……下一步：C# 代码 :)

         public partial class MainWindow : Window
         {  
               bool isSeekingMedia = false;
               DispatcherTimer seeker;   // the timer to update the Slider
               public MainWindow()
               {
                    InitializeComponent();
                    player = new MediaPLayer();
                    IsPlaying(false);
                    seeker = new DispatcherTimer();
                    seeker.Interval = TimeSpan.FromMilliseconds(200);
                    seeker.Tick += Seeker_Tick;
        }
    ///Seeker_Tick will update the Slider position while the video is playing
                private void Seeker_Tick(object sender, EventArgs e)
                {
                    try
                    {
                        MediatimeCounter.Content = String.Format("{0:hh}:{0:mm}:{0:ss}/{1:hh}:{1:mm}:{1:ss}", videoPlayer.Position, videoPlayer.NaturalDuration.TimeSpan);
                        if (!isSeekingMedia)
                        {
                            videoSlider.Value = videoPlayer.Position.TotalSeconds;
                        }
                    }
                    catch (Exception ex) { }
                }


//This code is going to set Seeking to true to avoid playing the video if the user is changing the slider position... it kinda causes a performance issue.. so it's better to update the video position once the slider dragging event is completed.
private void videoSlider_DragStarted(object sender, RoutedEventArgs e)
    {
        isSeekingMedia = true;
    }

//and this code is to update the video position based on the slider value.
private void videoSlider_DragCompleted(object sender, RoutedEventArgs e)
    {
        if (videoPlayer.Source != null)
        {
            isSeekingMedia = false;
            this.videoPlayer = player.SeekVideo(videoPlayer, videoSlider.Value);
        }
    }