Question

我已经实现了一个附加属性，当它的值发生变化时，它会改变媒体元素的位置。

附属物的定义如下：

public class MediaElementHelper
{
    public static void SetBindablePosition(UIElement element, TimeSpan value)
    {
        if (element == null)
        {
            throw new ArgumentNullException();
        }
        element.SetValue(BindablePositionProperty, value);
    }

    public static TimeSpan GetBindablePosition(UIElement element)
    {
        if (element == null)
        {
            throw new ArgumentNullException();
        }
        return (TimeSpan) element.GetValue(BindablePositionProperty);
    }

    private static void PostionPropertyChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
    {
        var richEditControl = obj as MediaElement;

        if (richEditControl != null)
        {
            richEditControl.Position = (TimeSpan) e.NewValue;
        }
    }

    public static readonly DependencyProperty BindablePositionProperty =
        DependencyProperty.RegisterAttached("BindablePosition",
            typeof (TimeSpan), typeof (MediaElementHelper),
            new FrameworkPropertyMetadata(new TimeSpan(), FrameworkPropertyMetadataOptions.BindsTwoWayByDefault,
                PostionPropertyChanged));
}

}

并在MainWindow中：

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
    }

    private void Button_OnClick(object sender, RoutedEventArgs e)
    {
        var newFileDialog = new OpenFileDialog();
        newFileDialog.ShowDialog();
        MediaElement.Source = new Uri(newFileDialog.FileName);
    }

    private void MediaElement_OnMediaOpened(object sender, RoutedEventArgs e)
    {
        Slider.Maximum = MediaElement.NaturalDuration.TimeSpan.TotalMilliseconds;
        Slider.SmallChange = 1;
        Slider.LargeChange = 5000;
    }
}

和xaml：

    <MediaElement Name="MediaElement"
                  Grid.Row="0"
                  loc:MediaElementHelper.BindablePosition="{Binding ElementName=Slider, Path=Value, Converter={StaticResource DoubleToTimeSpanConverter}}"
                  MediaOpened="MediaElement_OnMediaOpened" />

我的转换器类定义如下：

public class DoubleToTimeSpanConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return TimeSpan.FromMilliseconds((double) value);
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return System.Convert.ToDouble(((TimeSpan) value).Milliseconds);
    }
}

但是，当我拖动滑块的拇指时效果很好，但是当我什么都不做的时候，滑块的拇指不会自动移动。我该怎么做才能使这种绑定成为拖曳方式结合？

Answer 1

没有完美的方法 - 我过去解决它的方法是创建一个新的DispatcherTimer对象，它会轮询Position元素，并更新滑块。

// this is the timer
timerVideoTime = new DispatcherTimer();
            timerVideoTime.Interval = TimeSpan.FromSeconds(1);
            timerVideoTime.Tick += new EventHandler(timer_Tick);
            timerVideoTime.Start();
        }

// the actual timer handler.
void timer_Tick(object sender, EventArgs e)
        {
            // Check if the movie finished calculate it's total time
            if (MyMediaElement.NaturalDuration.TimeSpan.TotalSeconds > 0)
            {
                if (TotalTime.TotalSeconds > 0)
                {
                    var sliderValue = MyMediaElement.Position.TotalSeconds /
                                       TotalTime.TotalSeconds;

                    if(Slider.Value != sliderValue){
                      Slider.SetCurrentValue(Slider.ValueProperty, sliderValue); 
                    }
                }
            }

绑定MediaElement和滑块值

1 个答案: