Question

我有一个用于选择媒体类型的组合框。当选择.vmw，.mpeg或.avi文件时，我希望更改mediaelement的高度。如何使用MVVM方法实现这一目标？

提前致谢

Answer 1

您可以使用适当的转换器将MediaElement的Width和Height直接绑定到其Source属性，该转换器会根据媒体类型选择合适的大小：

<MediaElement
    Width="{Binding Path=Source, RelativeSource={RelativeSource Self}, Converter={StaticResource MediaElementSizeConverter}, ConverterParameter=Width}"
    Height="{Binding Path=Source, RelativeSource={RelativeSource Self}, Converter={StaticResource MediaElementSizeConverter}, ConverterParameter=Height}"/>

转换器：

public class MediaElementSizeConverter : IValueConverter
{
    private const double defaultWidth = 320d;
    private const double defaultHeight = 240d;
    private const double wmvWidth = 640d;
    private const double wmvHeight = 480d;

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        Uri source = value as Uri;

        if (source != null)
        {
            if (source.AbsolutePath.EndsWith(".wmv"))
            {
                return (parameter as string) == "Width" ? wmvWidth : wmvHeight;
            }

            // more media types ...
        }

        return (parameter as string) == "Width" ? defaultWidth : defaultHeight;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

Answer 2

一种解决方案是将ComboBox绑定到自创的MediaTypeDefinition类列表。

public class MediaTypeDefinition
{
    public string Name { get; set; }

    public int Height { get; set; }
}

然后，您可以将SelectedItem绑定到媒体元素的高度。

<ComboBox x:Name="mediaTypeList" ItemsSource="{Binding Definitions}" SelectedValuePath="Name" />

<MediaElement Height="{Binding SelectedItem.Height, Elementname=mediaTypeList}" />

根据组合框的选择改变元件高度

2 个答案: