WPF故事板不会暂停

Question

我有一个非常简单的故事板，其Int32Animation针对我班上的自定义DP。

我的DP有一个OnChanged回调，它有一个Console.WriteLine（“当前值：”+ MyDP）。

当我运行故事板时，我可以看到控制台输出正常，当我暂停故事板时，控制台输出停止，但是当我恢复故事板时，DP不是它应该的下一个值。即使故事板已停止，它仍在继续增加。

有没有人有这样的事情发生在他们身上？

这是我正在做的事情的代码片段

            Int32Animation element = new Int32Animation();
            element.From = 0;
            element.To = targetTo;
            element.Duration = dur;
            Storyboard.SetTargetProperty(element, new PropertyPath(CurrentFrameProperty));
            _filmstripStoryboard = new Storyboard {SpeedRatio = this.FrameRate};
            _filmstripStoryboard.Children.Add(element);


        public void Start()
        {
            _filmstripStoryboard.Begin(this, true);
        }

        public void Pause()
        {
            _filmstripStoryboard.Pause(this);
        }

        public void Unpause()
        {
            _filmstripStoryboard.Resume(this);
        }

Answer 1

MSDN中有一个线程论坛，Microsoft确认此行为（即使故事板暂停一段时间，当前值仍在继续）是当时（截至2006年）WPF版本中的一个错误。论坛主题包括建议的解决方法，具体来说，在您暂停时保存当前位置，并在您恢复时手动寻找相同的位置。

线程提到他们正在考虑在将来的版本中修复bug，但我不知道.NET 3.5或4.0是否实际修复了这个bug。

编辑：似乎在.NET 4.0中修复了错误 - 我能够暂停然后恢复动画，而不会在中间时间内向前跳跃。 （我没有在3.5中测试。）

Answer 2

现在4.0中没有错误。下面的代码工作正常。

<Window
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    x:Class="WpfAnimation.Win1805787"
    xmlns:Local="clr-namespace:WpfAnimation"
    x:Name="MyWindow"
    Title="Win1805787"
    Width="640" Height="480">

    <Grid x:Name="LayoutRoot">      

        <StackPanel HorizontalAlignment="Center" VerticalAlignment="Center">
            <TextBox HorizontalAlignment="Right" VerticalAlignment="Top" Width="75" Text="{Binding CurrentFrame, ElementName=MyWindow}" Height="20" Margin="5,0,5,5"/>
            <Button x:Name="Play1" Content="Play" HorizontalAlignment="Left" VerticalAlignment="Top" Width="75" Click="Play_Click" Margin="5,0,5,5"/>
            <Button x:Name="Pause1" Content="Pause" HorizontalAlignment="Right" VerticalAlignment="Top" Width="75" Click="Pause_Click" Margin="5,0,5,5"/>
            <Button x:Name="Resume1" Content="Resume" HorizontalAlignment="Right" VerticalAlignment="Top" Width="75" Click="Resume_Click" Margin="5,0,5,5"/>
        </StackPanel>

        </Grid>

</Window>   

/////////////////////////

 using System;
    using System.Collections.Generic;
    using System.Text;
    using System.Windows;
    using System.Windows.Controls;
    using System.Windows.Data;
    using System.Windows.Documents;
    using System.Windows.Input;
    using System.Windows.Media;
    using System.Windows.Media.Imaging;
    using System.Windows.Shapes;
    using System.Windows.Media.Animation;

    namespace WpfAnimation
    {
        /// <summary>
        /// Interaction logic for Win1805787.xaml
        /// </summary>
        public partial class Win1805787 : Window
        {
            public Win1805787()
            {
                this.InitializeComponent();

                _createStoryBoard();
                // Insert code required on object creation below this point.
            }

            public int CurrentFrame
            {
                get { return (int)GetValue(CurrentFrameProperty); }
                set { SetValue(CurrentFrameProperty, value); }
            }

            // Using a DependencyProperty as the backing store for CurrentFrame.  This enables animation, styling, binding, etc...
            public static readonly DependencyProperty CurrentFrameProperty =
                DependencyProperty.Register("CurrentFrame", typeof(int), typeof(Win1805787), 
                        new PropertyMetadata(0, new PropertyChangedCallback(OnValueChanged)));

            private static void OnValueChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
            {

            }

            Storyboard _filmstripStoryboard;

            void _createStoryBoard()
            {       
                Int32Animation element = new Int32Animation();
                element.From = 0;
                element.To = 100;
                element.Duration = Duration.Plus(new Duration(new TimeSpan(1000000000)));
                Storyboard.SetTargetProperty(element, new PropertyPath(CurrentFrameProperty));
                _filmstripStoryboard = new Storyboard { SpeedRatio = 0.5 };
                _filmstripStoryboard.Children.Add(element);
            }

            private void Play_Click(object sender, System.Windows.RoutedEventArgs e)
            {
                _filmstripStoryboard.Begin(this, true);
            }

            private void Pause_Click(object sender, System.Windows.RoutedEventArgs e)
            {
                _filmstripStoryboard.Pause(this);
            }

            private void Resume_Click(object sender, System.Windows.RoutedEventArgs e)
            {
                _filmstripStoryboard.Resume(this);
            }

        }
    }