Question

我想在listview中显示图像但我不知道应该怎么做。我的Guest类有方法GetGuestImage()它返回一个绝对路径。当这个文件存在时，应该加载，当不加载占位符图像时。

我怎么能意识到这一点？

<ListView x:Name="listview">
                    <ListView.View>
                        <GridView>
                            <GridViewColumn DisplayMemberBinding="{Binding GetGuestImage()}" Header="Image" />
                            <GridViewColumn DisplayMemberBinding="{Binding Vorname}" Header="Vorname" />
                            <GridViewColumn DisplayMemberBinding="{Binding Nachname}" Header="Nachname" />
                            <GridViewColumn DisplayMemberBinding="{Binding Postleitzahl}" Header="PLZ" />
                            <GridViewColumn DisplayMemberBinding="{Binding Ort}" Header="Ort" />
                            <GridViewColumn DisplayMemberBinding="{Binding Land}" Header="Land" />
                        </GridView>
                    </ListView.View>
                </ListView>

Answer 1

您可以使用CellTemplate和值转换器完成此操作：

<ListView x:Name="listview" xmlns:local="clr-namespace:WpfApplication1">
    <ListView.Resources>
        <local:ImageConverter x:Key="ImageConverter" />
    </ListView.Resources>
    <ListView.View>
        <GridView>
            <GridViewColumn Header="Image">
                <GridViewColumn.CellTemplate>
                    <DataTemplate>
                        <Image Source="{Binding Path=., Converter={StaticResource ImageConverter}}" />
                    </DataTemplate>
                </GridViewColumn.CellTemplate>
            </GridViewColumn>
            <GridViewColumn DisplayMemberBinding="{Binding Vorname}" Header="Vorname" />
            <GridViewColumn DisplayMemberBinding="{Binding Nachname}" Header="Nachname" />
            <GridViewColumn DisplayMemberBinding="{Binding Postleitzahl}" Header="PLZ" />
            <GridViewColumn DisplayMemberBinding="{Binding Ort}" Header="Ort" />
            <GridViewColumn DisplayMemberBinding="{Binding Land}" Header="Land" />
        </GridView>
    </ListView.View>
</ListView>

namespace WpfApplication1
{
    public class ImageConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            dynamic dataObject = value;
            if (dataObject != null)
            {
                string path = dataObject.GetGuestImage();
                if(System.IO.File.Exists(path))
                    return new Uri(dataObject.GetGuestImage(), UriKind.RelativeOrAbsolute);
            }

            return new Uri(@"c:\yourplaceholderimage.png", UriKind.RelativeOrAbsolute);
        }

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

但是，您无法直接绑定到GetGuestImage（）方法。另一个想法可能是通过数据对象类的Uri属性公开路径并绑定到此路径。那你就不需要转换器了：

<GridViewColumn Header="Image">
    <GridViewColumn.CellTemplate>
        <DataTemplate>
            <Image Source="{Binding GuestImage}" />
        </DataTemplate>
    </GridViewColumn.CellTemplate>
</GridViewColumn>

public class YourDataClass
{
    public Uri GuestImage
    {
        get { return new Uri(@"c:\picture.png", UriKind.RelativeOrAbsolute); }
    }

    //+ the other properties...
}

Answer 2

使用转换器。

public class NullGuestImageToPlaceholderConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        if (value == null || !File.Exists(value as string))
            return placeholderImage;

        return GetImage(value);
    }

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

XAML：

<ListView x:Name="listview">
    <ListView.View>
        <GridView>
            <GridViewColumn DisplayMemberBinding="{Binding GuestImage, Converter={StaticResource nullGuestImageConverter}}" Header="Image" />
            <!-- your other columns -->
        </GridView>
    </ListView.View>
</ListView>

我没有GetGuestImage实现或完整的XAML，所以我现在能做的最多。

nullGuestImageConverter应该是转换器的x:Key，在您的XAML资源中定义（如<UserControl.Resources>），而placeholderImage应该是如何实现的你检索所说的占位符图像（我猜想会出现在GetGuestImage()）。

事实上，我猜您可以简单地用Convert替换GetGuestImage方法的内容，但我无法确切知道。

Answer 3

首先，您需要绑定到属性而不是方法，DisplayMemberBinding仅支持切换到CellTemplate所需的基本绑定

<ListView x:Name="listview">
    <ListView.View>
        <GridView>
            <GridViewColumn Header="Image" >
               <GridViewColumn.CellTemplate>
                   <DataTemplate>
                       <Image Source="{Binding GuestImageProperty}" />
                   </DataTemplate>
               </GridViewColumn.CellTemplate>
            </GridViewColumn>
            <GridViewColumn DisplayMemberBinding="{Binding Vorname}" Header="Vorname" />
            <GridViewColumn DisplayMemberBinding="{Binding Nachname}" Header="Nachname" />
            <GridViewColumn DisplayMemberBinding="{Binding Postleitzahl}" Header="PLZ" />
            <GridViewColumn DisplayMemberBinding="{Binding Ort}" Header="Ort" />
            <GridViewColumn DisplayMemberBinding="{Binding Land}" Header="Land" />
        </GridView>
    </ListView.View>
</ListView>

然后你可以使用绑定的TargetNullValue和FallbackValue属性来处理缺失值

在WPF Listview中显示图像

3 个答案: