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。请致电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，可以使用 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...... - 滑块将更新玩家当前位置 - 计时器将每 300 毫秒更新一次滑块当前的玩家位置

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);
        }
    }

Answer 3

只有在加载媒体并且发生 MediaOpened 事件后才能设置 Position 属性。

using System.Windows;
using System.Windows.Controls;

namespace MediaElementDemo
{    
    public partial class MainWindow : Window
    {
        MediaElement mediaElement;
        readonly private string MediaFilename;

        public MainWindow()
        {
            InitializeComponent();
            
            MediaFilename = @"YourSampleMediaPath";

            mediaElement = new MediaElement()
            {
                Source = new Uri(MediaFilename),
                Clock = null,
                LoadedBehavior = MediaState.Manual,
                UnloadedBehavior = MediaState.Manual
            };

            mediaElement.MediaOpened += MediaElement_MediaOpened;
            mediaElement.Play(); // Trigger MediaOpened event
        }

        private void MediaElement_MediaOpened(object sender, RoutedEventArgs e)
        {                        
            mediaElement.Position = TimeSpan.FromSeconds(20); // Set position            
        }
    }
}