将网格控件中的多边形居中

Question

谁能告诉我如何在Grid控件的给定行/列中居中多边形对象？

我尝试过的例子来自msdn。

<Grid x:Name="LayoutRoot" >
  <Polygon Points="300,200 400,125 400,275 300,200" 
           Stroke="Purple" 
           StrokeThickness="2"
           HorizontalAlignment="Center"
           VerticalAlignment="Center" >
    <Polygon.Fill>
        <SolidColorBrush Color="Blue" Opacity="0.4" />
    </Polygon.Fill>
 </Polygon>

干杯，

还

Answer 1

添加属性： -

 HorizontalAlignment="Center" VerticalAlignment="Center"

到Polygon。

Answer 2

尽管多边形的边界隐含了高度和宽度，但它默认为容器的大小。

如果你只是设置

HorizontalAlignment="Center" VerticalAlignment="Center"

它将多边形的左上角定位在中心。

您还必须明确设置多边形的高度和宽度以使其居中并保留其边界

添加了尺寸的样本多边形Xaml：

<Grid x:Name="LayoutRoot">
   <Path Data="M0.5,41.5 L201,0.5 L302,115 L157.25,157 z" Fill="#FFF4F4F5" Stroke="Black" UseLayoutRounding="False" HorizontalAlignment="Center" VerticalAlignment="Center" Width="302.5" Height="157.5"/>
</Grid>

Answer 3

也许this answer也适用于此。

它使用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();
    }
}

并将其绑定在XAML中

<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＃中使用它，而不仅仅是在XAML中，你需要这个类

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);
        }
    }

}

像这样在XAML中使用它

<Canvas>
    <TextBlock Canvas.Left="40" Canvas.Top="40" TextAlignment="Center" Text="MMMMMM"
          local:Mover.MoveToMiddle="True"/>
</Canvas>

或者像C＃那样

Mover.SetMoveToMiddle(UIElement, true);

或者你可以操纵RenderTransform

另一种方法是绑定到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);
}

此替代方案的优点是附加属性的效果在Visual Studio设计器中可见（在设置Margin属性时不是这种情况）。

在XAML中，这将是这样的：

<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是对原始答案的质疑。这种方式应该适用于类UIElement的所有对象。

注意：所有信用都归到上述链接答案的原始海报