Question

我在播放gif文件的WPF窗口中添加了一个媒体元素。但我不知道如何在一定的秒数后停止播放GIF。

在我当前的实现中，gif播放指示用户如何在窗口加载时执行操作但我不希望gif在循环中播放，我希望能够在gif之后停止gif秒数。

是否可以通过媒体元素实现这一目标？

private void Window_Loaded(object sender, RoutedEventArgs e)
{
      // set the phrases to listen for and start listening
      listener.Phrases = PhrasesTextBox.Text;
      listener.StartListening();

      gifMediaElement.Play();

}

Answer 1

尝试使用AnimatedGIFControl：

在WPF中，MediaElement可以显示带有一些不太理想的限制的动画GIF图像：

必须使用绝对路径设置Source属性;
默认情况下不支持播放功能;
透明像素显示为黑色。

以下是使用AnimatedGIFControl的示例：

<强> XAML

<Window x:Class="CSWPFAnimatedGIF.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:CSWPFAnimatedGIF"
        Title="Animated GIF" Height="300" Width="300">

    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition/>
            <RowDefinition/>
        </Grid.RowDefinitions>

        <local:AnimatedGIFControl x:Name="GIFCtrl"/>

        <Button x:Name="btnStart" Width="70" Height="30" Margin="50" 
                HorizontalAlignment="Left" Grid.Row="1" Click="btnStart_Click">Start</Button>

        <Button x:Name="btnStop" Width="70" Height="30" Margin="50"
                HorizontalAlignment="Right" Grid.Row="1" Click="btnStop_Click">Stop</Button>        
    </Grid>
</Window>

<强> Code-behind

public class AnimatedGIFControl : System.Windows.Controls.Image
{
    private Bitmap _bitmap; // Local bitmap member to cache image resource
    private BitmapSource _bitmapSource;
    public delegate void FrameUpdatedEventHandler();


    /// <summary>
    /// Delete local bitmap resource
    /// Reference: http://msdn.microsoft.com/en-us/library/dd183539(VS.85).aspx
    /// </summary>
    [DllImport("gdi32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    static extern bool DeleteObject(IntPtr hObject);

    /// <summary>
    /// Override the OnInitialized method
    /// </summary>
    protected override void OnInitialized(EventArgs e)
    {
        base.OnInitialized(e);
        this.Loaded += new RoutedEventHandler(AnimatedGIFControl_Loaded);
        this.Unloaded += new RoutedEventHandler(AnimatedGIFControl_Unloaded);           
    }

    /// <summary>
    /// Load the embedded image for the Image.Source
    /// </summary>

    void AnimatedGIFControl_Loaded(object sender, RoutedEventArgs e)
    {
        // Get GIF image from Resources
        if (Properties.Resources.ProgressIndicator != null)
        {
            _bitmap = Properties.Resources.ProgressIndicator;
            Width = _bitmap.Width;
            Height = _bitmap.Height;

            _bitmapSource = GetBitmapSource();
            Source = _bitmapSource;  
        }             
    }

    /// <summary>
    /// Close the FileStream to unlock the GIF file
    /// </summary>
    private void AnimatedGIFControl_Unloaded(object sender, RoutedEventArgs e)
    {
        StopAnimate();
    }

    /// <summary>
    /// Start animation
    /// </summary>
    public void StartAnimate()
    {
        ImageAnimator.Animate(_bitmap, OnFrameChanged);
    }

    /// <summary>
    /// Stop animation
    /// </summary>
    public void StopAnimate()
    {
        ImageAnimator.StopAnimate(_bitmap, OnFrameChanged);
    }

    /// <summary>
    /// Event handler for the frame changed
    /// </summary>
    private void OnFrameChanged(object sender, EventArgs e)
    {
        Dispatcher.BeginInvoke(DispatcherPriority.Normal,
                               new FrameUpdatedEventHandler(FrameUpdatedCallback));
    }

    private void FrameUpdatedCallback()
    {
        ImageAnimator.UpdateFrames();

        if (_bitmapSource != null)
            _bitmapSource.Freeze();

        // Convert the bitmap to BitmapSource that can be display in WPF Visual Tree
        _bitmapSource = GetBitmapSource();
        Source = _bitmapSource;
        InvalidateVisual();
    }

    private BitmapSource GetBitmapSource()
    {
        IntPtr handle = IntPtr.Zero;                

        try
        {
            handle = _bitmap.GetHbitmap();
            _bitmapSource = Imaging.CreateBitmapSourceFromHBitmap(
                handle, IntPtr.Zero, Int32Rect.Empty, BitmapSizeOptions.FromEmptyOptions());
        }
        finally
        {
            if (handle != IntPtr.Zero)
                DeleteObject(handle);
        }

        return _bitmapSource;
    }
}

<强> Code Logic

使用ImageAnimator为具有基于时间的帧的GIF图像设置动画。
使用InvalidateVisual方法在另一个线程中渲染GIF图像的每一帧。
从Image控件派生，以便更容易用作图像控件。
处理转储资源以确保效率。

Answer 2

如果您想继续使用MediaElement类型，则一种方法是使用DispatcherTimer。您可以将其设置为在特定秒数内打勾，并关闭计时器和MediaElement。例如：

DispatcherTimer timer = new DispatcherTimer();
private void Window_Loaded(object sender, RoutedEventArgs e)
{
    //...
    gifMediaElement.Play();
    timer.Interval = TimeSpan.FromSeconds(5);
    timer.Start();
    timer.Tick += (o, args) =>
    {
        timer.Stop();
        gifMediaElement.Stop();
    };
    //...

如何在设定的持续时间后调用停止MediaElement？

2 个答案: