Windows Phone 7 Wrappanel可见性

Question

我有一个列表，以gridview样式显示一堆图像，以下是我的代码：

<controls:PanoramaItem x:Name="Pano_Photos" Header="photos">
        <ListBox x:Name="lstMemoriesPhoto" ItemsSource="{Binding MemoryList}">
            <i:Interaction.Triggers>
                <i:EventTrigger EventName="SelectionChanged" x:Name="ListPhotoSelectionChangedEventTrigger">
                    <GalaSoft_MvvmLight_Command:EventToCommand Command="{Binding NavigateToDetailPage}" PassEventArgsToCommand="True"/>
                </i:EventTrigger>
            </i:Interaction.Triggers>
            <ListBox.ItemsPanel>
                <ItemsPanelTemplate>
                    <toolkit:WrapPanel ItemWidth="130" ItemHeight="130" Visibility="{Binding MemoryPhoto,Converter={StaticResource PhotoConverter}}"/>
                </ItemsPanelTemplate>
            </ListBox.ItemsPanel>
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <Image Source="{Binding MemoryPhoto,Converter={StaticResource ByteImageConverter}}" Margin="5"/>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>        
    </controls:PanoramaItem>

PhotoConverter检查MemoryPhoto变量并返回Visibility.Visible或Collapse，具体取决于MemoryPhoto变量是否为null。以下是PhotoConverter的代码：

  public class PhotoConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        try
        {
            if ((value is byte[]) && (value != null))
            {
                return Visibility.Visible;
            }
            return Visibility.Collapsed;
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }

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

但是当我运行我的应用程序时，我得到了这个结果，。第二个网格应该是不可见的，因为它包含空图像变量。

有人知道如何禁用wrappanel中的单个项目吗？非常感谢

修改 我想我找到了解决我的问题的方法，在图像控件中定义宽度和高度而不是在wrappanel中，代码是

<ListBox.ItemsPanel>
                    <ItemsPanelTemplate>
                        <toolkit:WrapPanel/>
                    </ItemsPanelTemplate>
                </ListBox.ItemsPanel>
                <ListBox.ItemTemplate>
                    <DataTemplate>
                        <Image Source="{Binding MemoryPhoto,Converter={StaticResource ByteImageConverter}}" Margin="5" Visibility="{Binding MemoryPhoto,Converter={StaticResource PhotoConverter}}" width="130" height="130"/>
                    </DataTemplate>
                </ListBox.ItemTemplate>

Answer 1

首先请修改您的转换器：

public class PhotoConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        try
        {
            if ((value is byte[]) && (value != null))
                return Visibility.Visible;
            else
                return Visibility.Collapsed;
        }

        catch (Exception ex)
        {
            throw ex;
            return Visibility.Collapsed;
        }
    }

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

然后修复你的XAML

<controls:PanoramaItem x:Name="Pano_Photos" Header="photos">
    <ListBox x:Name="lstMemoriesPhoto" ItemsSource="{Binding MemoryList}">
        <i:Interaction.Triggers>
            <i:EventTrigger EventName="SelectionChanged" x:Name="ListPhotoSelectionChangedEventTrigger">
                <GalaSoft_MvvmLight_Command:EventToCommand Command="{Binding NavigateToDetailPage}" PassEventArgsToCommand="True"/>
            </i:EventTrigger>
        </i:Interaction.Triggers>
        <ListBox.ItemsPanel>
            <ItemsPanelTemplate>
                <toolkit:WrapPanel ItemWidth="130" ItemHeight="130"/>
            </ItemsPanelTemplate>
        </ListBox.ItemsPanel>
        <ListBox.ItemTemplate>
            <DataTemplate>
                <Image Source="{Binding MemoryPhoto,Converter={StaticResource ByteImageConverter}}" Visibility="{Binding MemoryPhoto, Converter={StaticResource PhotoConverter}}" Margin="5"/>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>        
</controls:PanoramaItem>