问题：
.gif加载，但在使用GifSourcePropertyChanged进行更新时无法播放？ 关于.gif loading：
目前，我使用U.IsValidURL()让new Uri无法投放Exception。这是因为我需要GifImage加载应用程序，然后从ViewModel更新。在GifSourcePropertyChanged被调用之前一切正常，然后更新local:GifImage，但.gif不会播放（我相信它会加载MediaElement并行加载{{1在local:GifImage加载的地方变成黑色。如果我从头开始对.gif进行硬编码，Uri加载并播放就好了。
示例XAML：
local:GifImage示例ViewModel：
<local:GifImage
GifSource="{
Binding Path=myGifImage,
UpdateSourceTrigger=PropertyChanged,
Mode=OneWay}"
AutoStart="True"/>
示例GifImage类：
public class ViewModel: INotifyPropertyChanged
{
private string _myGifImage;
public string myGifImage
{
get { return this._myGifImage; }
set
{
this._myGifImage = value;
this.OnPropertyChanged("myGifImage");
}
}
}
我从某个地方得到了public class GifImage : Image
{
#region Memmbers
private GifBitmapDecoder _gifDecoder;
private Int32Animation _animation;
private bool _isInitialized;
#endregion Memmbers
#region Properties
private int FrameIndex
{
get { return (int)GetValue(FrameIndexProperty); }
set { SetValue(FrameIndexProperty, value); }
}
private static readonly DependencyProperty FrameIndexProperty =
DependencyProperty.Register("FrameIndex", typeof(int), typeof(GifImage), new FrameworkPropertyMetadata(0, new PropertyChangedCallback(ChangingFrameIndex)));
private static void ChangingFrameIndex(DependencyObject obj, DependencyPropertyChangedEventArgs ev)
{
GifImage image = obj as GifImage;
image.Source = image._gifDecoder.Frames[(int)ev.NewValue];
}
/// <summary>
/// Defines whether the animation starts on it's own
/// </summary>
public bool AutoStart
{
get { return (bool)GetValue(AutoStartProperty); }
set { SetValue(AutoStartProperty, value); }
}
public static readonly DependencyProperty AutoStartProperty =
DependencyProperty.Register("AutoStart", typeof(bool), typeof(GifImage), new UIPropertyMetadata(false, AutoStartPropertyChanged));
private static void AutoStartPropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
{
if ((bool)e.NewValue)
(sender as GifImage).StartAnimation();
}
public string GifSource
{
get { return (string)GetValue(GifSourceProperty); }
set { SetValue(GifSourceProperty, value); }
}
public static readonly DependencyProperty GifSourceProperty =
DependencyProperty.Register("GifSource", typeof(string), typeof(GifImage), new UIPropertyMetadata(string.Empty, GifSourcePropertyChanged));
private static void GifSourcePropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
{
// CARLO 20100622: Reinitialize animation everytime image is changed
(sender as GifImage).Initialize();
}
#endregion Properties
#region Private Instance Methods
private void Initialize()
{
if (U.IsValidURL(this.GifSource, UriKind.Absolute))
{
_gifDecoder = new GifBitmapDecoder(
new Uri(this.GifSource),
BitmapCreateOptions.PreservePixelFormat,
BitmapCacheOption.Default);
_animation = new Int32Animation(0, _gifDecoder.Frames.Count - 1, new Duration(new TimeSpan(0, 0, 0, _gifDecoder.Frames.Count / 10, (int)((_gifDecoder.Frames.Count / 10.0 - _gifDecoder.Frames.Count / 10) * 1000))));
_animation.RepeatBehavior = RepeatBehavior.Forever;
this.Source = _gifDecoder.Frames[0];
_isInitialized = true;
}
}
#endregion Private Instance Methods
#region Public Instance Methods
/// <summary>
/// Shows and starts the gif animation
/// </summary>
public void Show()
{
this.Visibility = Visibility.Visible;
this.StartAnimation();
}
/// <summary>
/// Hides and stops the gif animation
/// </summary>
public void Hide()
{
this.Visibility = Visibility.Collapsed;
this.StopAnimation();
}
/// <summary>
/// Starts the animation
/// </summary>
public void StartAnimation()
{
if (!_isInitialized)
this.Initialize();
BeginAnimation(FrameIndexProperty, _animation);
}
/// <summary>
/// Stops the animation
/// </summary>
public void StopAnimation()
{
BeginAnimation(FrameIndexProperty, null);
}
#endregion Public Instance Methods
}
（我不记得哪个问题，GifImage和WPF上有几个问题。 .gifs是唯一一个没有大量错误的课程（至少对我而言）。
答案 0 :(得分：2)
不确定您的代码有什么问题，但您可以尝试使用this attached property代替：
<Image my:ImageBehavior.AnimatedSource="{Binding Path=myGifImage}"/>