IsPressed 触发器（按钮）导致异常答案

【问题标题】：IsPressed Trigger (Button) cause ExceptionIsPressed 触发器（按钮）导致异常
【发布时间】：2012-05-03 19:35:51
【问题描述】：

我正在尝试覆盖按钮样式。其实我已经做了几十次了，但现在我遇到了这个：

异常和内部异常： {“触发器中的属性不能为空。”}

我的代码：

<Style x:Key="ArrowRightStyle" TargetType="{x:Type Button}">
    <Setter Property="FocusVisualStyle" Value="{StaticResource ButtonFocusVisual}"/>
    <Setter Property="Background" Value="{StaticResource ButtonNormalBackground}"/>
    <Setter Property="BorderBrush" Value="{StaticResource ButtonNormalBorder}"/>
    <Setter Property="BorderThickness" Value="0"/>
    <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/>
    <Setter Property="HorizontalContentAlignment" Value="Center"/>
    <Setter Property="VerticalContentAlignment" Value="Center"/>
    <Setter Property="Padding" Value="1"/>
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate>
                <Grid Height="{Binding ElementName=imgBackground, Path=ActualHeight, Mode=OneWay}" 
                      Width="{Binding ElementName=imgBackground, Path=ActualWidth, Mode=OneWay}">
                    <Image x:Name="imgBackground" Source="{StaticResource RightArrowImageNormal}" Stretch="None"/>
                </Grid>
                <ControlTemplate.Triggers>
                    <Trigger Property="IsEnabled" Value="False">
                        <Setter TargetName="imgBackground" Property="Source" Value="{StaticResource RightArrowImageDisabled}"/>
                    </Trigger>
                    <Trigger Property="IsPressed" Value="True">
                        <Setter TargetName="imgBackground" Property="Source" Value="{StaticResource RightArrowImageIsPressed}"/>
                    </Trigger>
                </ControlTemplate.Triggers>
            </ControlTemplate>
        </Setter.Value>
    </Setter>

</Style>

所以它起作用了：

    <Style x:Key="ArrowRightStyle" TargetType="{x:Type Button}">
    <Setter Property="FocusVisualStyle" Value="{StaticResource ButtonFocusVisual}"/>
    <Setter Property="Background" Value="{StaticResource ButtonNormalBackground}"/>
    <Setter Property="BorderBrush" Value="{StaticResource ButtonNormalBorder}"/>
    <Setter Property="BorderThickness" Value="0"/>
    <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/>
    <Setter Property="HorizontalContentAlignment" Value="Center"/>
    <Setter Property="VerticalContentAlignment" Value="Center"/>
    <Setter Property="Padding" Value="1"/>
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate>
                <Grid Height="{Binding ElementName=imgBackground, Path=ActualHeight, Mode=OneWay}" 
                      Width="{Binding ElementName=imgBackground, Path=ActualWidth, Mode=OneWay}">
                    <Image x:Name="imgBackground" Source="{StaticResource RightArrowImageNormal}" Stretch="None"/>
                </Grid>
                <ControlTemplate.Triggers>
                    <Trigger Property="IsEnabled" Value="False">
                        <Setter TargetName="imgBackground" Property="Source" Value="{StaticResource RightArrowImageDisabled}"/>
                    </Trigger>
                    <DataTrigger Binding="{Binding RelativeSource={RelativeSource Mode=Self}, Path=IsPressed}" Value="True">
                        <Setter TargetName="imgBackground"
                                Property="Source" Value="{StaticResource RightArrowImageIsPressed}"/>
                    </DataTrigger>
                </ControlTemplate.Triggers>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

为什么？？？？

【问题讨论】：

标签： wpf templates button triggers styles

【解决方案1】：

快速浏览一下，我认为它找不到属性 IsPressed

添加“按钮”。应该这样做。

....
  <Trigger Property="Button.IsPressed" Value="True">
     <Setter TargetName="imgBackground" Property="Source" Value="{StaticResource....

或确保您的模板以按钮为目标（我知道您在样式中指定了该按钮，但这还不够 - 模板将假定 typeof(Control) 并且控件上没有 IsPressed。

...
<Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type Button}">
            ....the rest of your code

我认为

{Binding RelativeSource={RelativeSource Mode=Self}, Path=IsPressed}"

在运行时将相对源的类型解析为“Button”，因此能够找到 IsPressed...

【讨论】：