也许这个答案在这里也适用。
它使用了一个CenterConverter
public class CenterConverter : IMultiValueConverter
{
public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
{
if (values[0] == DependencyProperty.UnsetValue || values[1] == DependencyProperty.UnsetValue)
{
return DependencyProperty.UnsetValue;
}
double width = (double) values[0];
double height = (double)values[1];
return new Thickness(-width/2, -height/2, 0, 0);
}
public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
然后在XAML中像这样绑定它
<Canvas>
<TextBlock x:Name="txt" Canvas.Left="40" Canvas.Top="40" TextAlignment="Center" Text="MMMMMM">
<TextBlock.Margin>
<MultiBinding Converter="{StaticResource centerConverter}">
<Binding ElementName="txt" Path="ActualWidth"/>
<Binding ElementName="txt" Path="ActualHeight"/>
</MultiBinding>
</TextBlock.Margin>
</TextBlock>
<Rectangle Canvas.Left="39" Canvas.Top="39" Width="2" Height="2" Fill="Red"/>
</Canvas>
为了能够在 C# 中使用,而不仅仅是在 XAML 中,您需要这个类。
public class Mover : DependencyObject
{
public static readonly DependencyProperty MoveToMiddleProperty =
DependencyProperty.RegisterAttached("MoveToMiddle", typeof (bool), typeof (Mover),
new PropertyMetadata(false, PropertyChangedCallback));
public static void SetMoveToMiddle(UIElement element, bool value)
{
element.SetValue(MoveToMiddleProperty, value);
}
public static bool GetMoveToMiddle(UIElement element)
{
return (bool) element.GetValue(MoveToMiddleProperty);
}
private static void PropertyChangedCallback(DependencyObject sender, DependencyPropertyChangedEventArgs e)
{
FrameworkElement element = sender as FrameworkElement;
if (element == null)
{
return;
}
if ((bool)e.NewValue)
{
MultiBinding multiBinding = new MultiBinding();
multiBinding.Converter = new CenterConverter();
multiBinding.Bindings.Add(new Binding("ActualWidth") {Source = element});
multiBinding.Bindings.Add(new Binding("ActualHeight") {Source = element});
element.SetBinding(FrameworkElement.MarginProperty, multiBinding);
}
else
{
element.ClearValue(FrameworkElement.MarginProperty);
}
}
}
在 XAML 中使用它如下所示
<Canvas>
<TextBlock Canvas.Left="40" Canvas.Top="40" TextAlignment="Center" Text="MMMMMM"
local:Mover.MoveToMiddle="True"/>
</Canvas>
或者在C#中这样写
Mover.SetMoveToMiddle(UIElement, true);
或者,您可以操作 RenderTransform
另一种选择是绑定到 RenderTransform 而不是 Margin。在这种情况下,转换器将返回
return new TranslateTransform(-width / 2, -height / 2);
附加属性的回调方法将包含以下行:
if ((bool)e.NewValue)
{
...
element.SetBinding(UIElement.RenderTransformProperty, multiBinding);
}
else
{
element.ClearValue(UIElement.RenderTransformProperty);
}
这种替代方式的优点是,所附属性的效果可以在Visual Studio设计器中看到(而在设置Margin属性时不行)。
在XAML中,它会像这样显示:
<Canvas>
<TextBlock x:Name="txt" Canvas.Left="40" Canvas.Top="40" TextAlignment="Center" Text="MMMMMM">
<TextBlock.RenderTransform>
<MultiBinding Converter="{StaticResource centerConverter}">
<Binding ElementName="txt" Path="ActualWidth"/>
<Binding ElementName="txt" Path="ActualHeight"/>
</MultiBinding>
</TextBlock.RenderTransform>
</TextBlock>
<Rectangle Canvas.Left="39" Canvas.Top="39" Width="2" Height="2" Fill="Red"/>
</Canvas>
TextBlock
是原始答案中提到的控件。这种方法适用于类中的所有对象 UIElement
。
注意:以上链接答案的所有功劳归原作者所有。