WPF媒体元素.位置不起作用

本文关键字：不起作用 位置 元素 媒体 WPF | 更新日期: 2023-09-27 18:00:30

我需要的是在WPF的MediaElement控件上设置Position属性。但当我播放视频时（无论是通过Play()还是通过Opacity上的某种动画），它根本不起作用。它显示的是00:00:00时间，但我希望它设置为00:00:05。

我有一个硬编码的位置值，它根本不起作用。

万一我要把我所有的代码都放进去，这样你就可以看到整个动画逻辑了。

有线索吗？

  public partial class CrossFadeTransition : UserControl
    {
        DoubleAnimation _doubleAnimationFrontPlayer = new DoubleAnimation();
        DoubleAnimation _doubleAnimationBackPlayer = new DoubleAnimation();
        Storyboard _sb1 = new Storyboard();
        Storyboard _sb2 = new Storyboard();
        public TimeSpan Duration = TimeSpan.FromSeconds(2);
        public Dictionary<string, Position2D> PlayerPosition { set; get; }
        public CrossFadeTransition()
        {
            InitializeComponent();
            Player1.LoadedBehavior = MediaState.Manual;
            Player1.UnloadedBehavior = MediaState.Stop;
            Player2.LoadedBehavior = MediaState.Manual;
            Player2.UnloadedBehavior = MediaState.Stop;
            PlayerPosition = new Dictionary<string, Position2D>();
            PlayerPosition.Add("Player1", Position2D.Front);
            PlayerPosition.Add("Player2", Position2D.Back);
        }
        Position2D positionPlayer1;
        Position2D positionPlayer2;
        public void Stop()
        {
            if (Player1.IsEnabled)
                Player1.Stop();
            if (Player2.IsEnabled)
                Player2.Stop();
        }
        public void Start(Uri uri, int? position)
        {
            try
            {
                positionPlayer1 = PlayerPosition["Player1"];
                positionPlayer2 = PlayerPosition["Player2"];
                if (positionPlayer1 == Library.Position2D.Back)
                {
                    Player1.Source = uri;
                    if (Player1.IsEnabled)
                        Player1.Stop();
                    Player1.Position = TimeSpan.FromSeconds(5); // IT IS NOT WORKING !!!
                    Player1.Play();
                }
                if (positionPlayer2 == Library.Position2D.Back)
                {
                    Player2.Source = uri;
                    if (Player2.IsEnabled)
                        Player2.Stop();
                    Player2.Position = TimeSpan.FromSeconds(5); // IT IS NOT WORKING !!!
                    Player2.Play();
                }

                _sb1.Children.Clear();
                _sb2.Children.Clear();

                if (positionPlayer1 == Position2D.Front)
                {
                    _doubleAnimationFrontPlayer.From = 1;
                    _doubleAnimationFrontPlayer.To = 0;
                    _doubleAnimationFrontPlayer.Duration = new Duration(Duration);
                    PlayerPosition["Player1"] = Position2D.Back;
                }
                else if (positionPlayer1 == Position2D.Back)
                {
                    _doubleAnimationFrontPlayer.From = 0;
                    _doubleAnimationFrontPlayer.To = 1;
                    _doubleAnimationFrontPlayer.Duration = new Duration(Duration);
                    PlayerPosition["Player1"] = Position2D.Front;
                }
                if (positionPlayer2 == Position2D.Front)
                {
                    _doubleAnimationBackPlayer.From = 1;
                    _doubleAnimationBackPlayer.To = 0;
                    _doubleAnimationBackPlayer.Duration = new Duration(Duration);
                    PlayerPosition["Player2"] = Position2D.Back;
                }
                else if (positionPlayer2 == Position2D.Back)
                {
                    _doubleAnimationBackPlayer.From = 0;
                    _doubleAnimationBackPlayer.To = 1;
                    _doubleAnimationBackPlayer.Duration = new Duration(Duration);
                    PlayerPosition["Player2"] = Position2D.Front;
                }
                _sb1.Children.Add(_doubleAnimationFrontPlayer);
                Storyboard.SetTargetProperty(_doubleAnimationFrontPlayer, new PropertyPath("(Panel.Opacity)"));
                Storyboard.SetTarget(_doubleAnimationFrontPlayer, Player1);
                _sb1.Completed += _sb1_Completed;
                _sb1.Begin();
                //
                _sb2.Children.Add(_doubleAnimationBackPlayer);
                Storyboard.SetTargetProperty(_doubleAnimationBackPlayer, new PropertyPath("(Panel.Opacity)"));
                Storyboard.SetTarget(_doubleAnimationBackPlayer, Player2);
                _sb2.Completed += _sb2_Completed;
                _sb2.Begin();
            }
            catch (Exception)
            {
                throw;
            }
        }
        void _sb2_Completed(object sender, EventArgs e)
        {
            _sb2.Completed -= _sb2_Completed;
            Debug.WriteLine("Player2 COMPLETED " + DateTime.Now.TimeOfDay);
            if (positionPlayer2 == Position2D.Front)
            {
                Player2.Stop();
            }
        }
        void _sb1_Completed(object sender, EventArgs e)
        {
            _sb1.Completed -= _sb1_Completed;
            Debug.WriteLine("Player1 COMPLETED " + DateTime.Now.TimeOfDay);
            if (positionPlayer1 == Position2D.Front)
            {
                Player1.Stop();
            }
        }
    }

我试着像一样

Player2.Play();
Player2.Pause();
Player2.Position = TimeSpan.FromSeconds(5); // IT IS NOT WORKING !!!
Player2.Play();

但没有快乐。。。

WPF媒体元素.位置不起作用

我找到了一些解决方案。它并不完全理想，因为有时它会显示第一个视频帧，但至少它是有效的。

  1. 我们需要那些可以应用新Position的事件。

    void Player2_MediaOpened(object sender, RoutedEventArgs e)
{
     Player2.Position = new TimeSpan(0, 0, 7);
}
void Player1_MediaOpened(object sender, RoutedEventArgs e)
{
    Player1.Position = new TimeSpan(0, 0, 7);
}

  2. 我们必须像这样关闭Mediaelement。

    Player1.Stop();
Player1.Close();
Player1.Source = uri;
Player1.Play();

玩得开心！（啤酒）

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