DataTemplate将多个数据触发器转换为相同的元素和属性

Question

如何在同一元素和属性上使用多个数据触发器？

        <DataTemplate.Triggers>
            <DataTrigger Binding="{Binding ElementName=RootGrid,Path=IsMouseOver}" Value="True">
                <Setter TargetName="SelectionGrid" Property="Opacity" Value="0.5" />
            </DataTrigger>
            <DataTrigger Binding="{Binding ElementName=RootGrid,Path=IsMouseOver}" Value="False">
                <Setter TargetName="SelectionGrid" Property="Opacity" Value="0.0" />
            </DataTrigger>
            <DataTrigger Binding="{Binding Selected}" Value="True">
                <Setter TargetName="SelectionGrid" Property="Opacity" Value="1.0" />
            </DataTrigger>
            <DataTrigger Binding="{Binding Selected}" Value="False">
                <Setter TargetName="SelectionGrid" Property="Opacity" Value="0" />
            </DataTrigger>
        </DataTemplate.Triggers>

注意我是如何定位SelectionGrid的Opacity财产.我怎样才能达到这个效果？这应该复制Windows 7具有的悬停选择框.所以,当两者都是,Selected并且IsMouseOver,我希望它向我展示Selected状态.

Answer 1

您可以使用MultiDataTrigger或DataTrigger使用a MultiBinding和BooleanOrConverter.

但我认为对您的问题最简单的解决方案是使用MultiBindingfor Opacity绑定到两者Selected和IsMouseOver

<DataTemplate>
    <Grid x:Name="SelectionGrid">
        <Grid.Opacity>
            <MultiBinding Converter="{StaticResource OpacityConverter}"> 
                <Binding RelativeSource="{RelativeSource Self}" Path="IsMouseOver"/>
                <Binding Path="Selected"/>
            </MultiBinding>
        </Grid.Opacity>
    </Grid>
    <!-- ... -->
</DataTemplate>

在OpacityConverter中,您可以决定Opacity值

public class OpacityConverter : IMultiValueConverter
{
    public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        bool isMouseOver = (bool)values[0];
        bool selected = (bool)values[1];
        if (selected == true)
        {
            return 1.0;
        }
        else if (isMouseOver == true)
        {
            return 0.5;
        }
        return 0.0;
    }
    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotSupportedException();
    }
}

编辑:以下是如何用a DataTrigger和MultiDataTrigger

<DataTemplate>
    <Grid x:Name="SelectionGrid"
            Opacity="0"
            Background="Blue">
    </Grid>
    <DataTemplate.Triggers>
        <DataTrigger Binding="{Binding Path=Selected}" Value="True">
            <Setter TargetName="SelectionGrid" Property="Opacity" Value="1.0"/>
        </DataTrigger>
        <MultiDataTrigger>
            <MultiDataTrigger.Conditions>
                <Condition Binding="{Binding ElementName=SelectionGrid, Path=IsMouseOver}" Value="True"/>
                <Condition Binding="{Binding Path=Selected}" Value="False"/>
            </MultiDataTrigger.Conditions>
            <Setter TargetName="SelectionGrid" Property="Opacity" Value="0.5"/>
        </MultiDataTrigger>
    </DataTemplate.Triggers>
</DataTemplate>