为什么Projection属性为null？
为什么Projection属性为null？
提问于 2011-11-14 02:26:22
<ListBox Name="listBoxButtons"
Height="700">
<ListBox.ItemTemplate>
<DataTemplate>
<Border Background="{StaticResource PhoneAccentBrush}"
Name="border"
Width="432" Height="62"
Margin="6" Padding="12,0,0,6">
<TextBlock Text="{Binding}"
Foreground="#FFFFFF" FontSize="26.667"
HorizontalAlignment="Left"
VerticalAlignment="Bottom"
FontFamily="{StaticResource PhoneFontFamilySemiBold}"/>
<Border.Projection>
<PlaneProjection RotationX="-60"/>
</Border.Projection>
</Border>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>代码：
private void ShowAnim()
{
IEasingFunction quadraticEase = new QuadraticEase { EasingMode = EasingMode.EaseOut };
Storyboard _swivelShow = new Storyboard();
foreach (var item in this.listBoxButtons.Items)
{
UIElement container = listBoxButtons.ItemContainerGenerator.ContainerFromItem(item) as UIElement;
if (container != null)
{
Border content = VisualTreeHelper.GetChild(container, 0) as Border;
if (content != null)
{
DoubleAnimationUsingKeyFrames showAnimation = new DoubleAnimationUsingKeyFrames();
EasingDoubleKeyFrame showKeyFrame1 = new EasingDoubleKeyFrame();
showKeyFrame1.KeyTime = TimeSpan.FromMilliseconds(0);
showKeyFrame1.Value = -60;
showKeyFrame1.EasingFunction = quadraticEase;
EasingDoubleKeyFrame showKeyFrame2 = new EasingDoubleKeyFrame();
showKeyFrame2.KeyTime = TimeSpan.FromMilliseconds(85);
showKeyFrame2.Value = 0;
showKeyFrame2.EasingFunction = quadraticEase;
showAnimation.KeyFrames.Add(showKeyFrame1);
showAnimation.KeyFrames.Add(showKeyFrame2);
Storyboard.SetTargetProperty(showAnimation, new PropertyPath(PlaneProjection.RotationXProperty));
Storyboard.SetTarget(showAnimation, content.Projection);
_swivelShow.Children.Add(showAnimation);
}
}
}
_swivelShow.Begin();
}但是：Storyboard.SetTarget(showAnimation, content.Projection)抛出了一个异常。content.Projection为null。这怎么会发生呢？
回答 1
Stack Overflow用户
回答已采纳
发布于 2011-11-14 04:52:04
您看到的是错误的Border元素。在您的案例中，项目容器的层次结构类似于Border -> ContentControl -> ContentPresenter -> container (这是您的)。因此，您必须深入容器的子层次结构以找到您想要的边框。
下面的代码递归地搜索UIElement的子级，并给出一些调试输出，以便您可以看到它有多深入。当它找到名为“border”的控件时，它将停止：
private UIElement GetMyBorder(UIElement container)
{
if (container is FrameworkElement && ((FrameworkElement)container).Name == "border")
return container;
for (int i = 0; i < VisualTreeHelper.GetChildrenCount(container); i++)
{
var child = (FrameworkElement)VisualTreeHelper.GetChild(container, i);
System.Diagnostics.Debug.WriteLine("Found child "+ child.ToString());
System.Diagnostics.Debug.WriteLine("Going one level deeper...");
UIElement foundElement = GetMyBorder(child);
if (foundElement != null)
return foundElement;
}
return null;
}要使用它：
Border content = (Border)GetMyBorder(container);页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/8113670
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