如何捕获鼠标单击事件到重叠的ItemsControl

Question

我想用WPF开发一种矢量图像编辑器。 具有相同形式的每个形状都放在ItemsControl中。 至少有4种形状（线条，矩形，位图等）。 问题是：

我无法从另一层下面的图层中单击形状。

要求：

1. ItemsControl ItemsPanelTemplate必须是Canvas，大小不能为0。
2. 可以随时点击每个形状，而无需在可点击的形状上激活IsHitTestVisible。

问题：

如何在上面的ItemsControl中单击其他形状下方的形状？

编辑1： 添加代码段

<Grid>
    <!--Array of Ellipses-->
    <ItemsControl ItemsSource="{Binding EllipseSource}">
        <ItemsControl.ItemsPanel>
            <ItemsPanelTemplate>
                <Canvas />
            </ItemsPanelTemplate>
        </ItemsControl.ItemsPanel>
        <ItemsControl.ItemContainerStyle>
            <Style TargetType="ContentPresenter">
                <Setter Property="Canvas.Left" Value="{Binding Path=Distance}" />
                <Setter Property="Canvas.Width" Value="10" />
                <Setter Property="Canvas.Top" Value="{Binding Path=Top}" />
                <Setter Property="Canvas.Height" Value="10" />
            </Style>
        </ItemsControl.ItemContainerStyle>
        <ItemsControl.ItemTemplate>
            <Ellipse MouseDown="EllipseOnMouseDown" />
        </ItemsControl.ItemTemplate>
    </ItemsControl>

    <!--Array of Rectangles-->
    <ItemsControl ItemsSource="{Binding RectangleSource}">
        <ItemsControl.ItemsPanel>
            <ItemsPanelTemplate>
                <Canvas />
            </ItemsPanelTemplate>
        </ItemsControl.ItemsPanel>
        <ItemsControl.ItemContainerStyle>
            <Style TargetType="ContentPresenter">
                <Setter Property="Canvas.Left" Value="{Binding Path=Distance}" />
                <Setter Property="Canvas.Width" Value="10" />
                <Setter Property="Canvas.Top" Value="{Binding Path=Top}" />
                <Setter Property="Canvas.Height" Value="10" />
            </Style>
        </ItemsControl.ItemContainerStyle>
        <ItemsControl.ItemTemplate>
            <Rectangle MouseDown="RectangleOnMouseDown" />
        </ItemsControl.ItemTemplate>
    </ItemsControl>
</Grid>

Answer 1

注意：

• 将您的网格控件命名为grid
• 将您的功能RectangleOnMouseDown和EllipseOnMouseDown更改为shape_MouseLeftButtonDown

您可以使用： XAML：

<Grid name="grid">
    <!--Array of Ellipses-->
    <ItemsControl ItemsSource="{Binding EllipseSource}">
        <ItemsControl.ItemsPanel>
            <ItemsPanelTemplate>
                <Canvas />
            </ItemsPanelTemplate>
        </ItemsControl.ItemsPanel>
        <ItemsControl.ItemContainerStyle>
            <Style TargetType="ContentPresenter">
                <Setter Property="Canvas.Left" Value="{Binding Path=Distance}" />
                <Setter Property="Canvas.Width" Value="10" />
                <Setter Property="Canvas.Top" Value="{Binding Path=Top}" />
                <Setter Property="Canvas.Height" Value="10" />
            </Style>
        </ItemsControl.ItemContainerStyle>
        <ItemsControl.ItemTemplate>
            <Ellipse MouseDown="shape_MouseLeftButtonDown" />
        </ItemsControl.ItemTemplate>
    </ItemsControl>

    <!--Array of Rectangles-->
    <ItemsControl ItemsSource="{Binding RectangleSource}">
        <ItemsControl.ItemsPanel>
            <ItemsPanelTemplate>
                <Canvas />
            </ItemsPanelTemplate>
        </ItemsControl.ItemsPanel>
        <ItemsControl.ItemContainerStyle>
            <Style TargetType="ContentPresenter">
                <Setter Property="Canvas.Left" Value="{Binding Path=Distance}" />
                <Setter Property="Canvas.Width" Value="10" />
                <Setter Property="Canvas.Top" Value="{Binding Path=Top}" />
                <Setter Property="Canvas.Height" Value="10" />
            </Style>
        </ItemsControl.ItemContainerStyle>
        <ItemsControl.ItemTemplate>
            <Rectangle MouseDown="shape_MouseLeftButtonDown" />
        </ItemsControl.ItemTemplate>
    </ItemsControl>
</Grid>

代码：

List<DependencyObject> hitResultsList = new List<DependencyObject>();

// Return the result of the hit test to the callback.
public HitTestResultBehavior MyHitTestResult(HitTestResult result)
{
    hitResultsList.Add(result.VisualHit);
    return HitTestResultBehavior.Continue;
}

private void shape_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
    Point pt = Mouse.GetPosition(grid);
    hitResultsList.Clear();
    VisualTreeHelper.HitTest(grid, null, new HitTestResultCallback(MyHitTestResult), new PointHitTestParameters(pt));

    foreach (var ee in hitResultsList)
    {
        if(ee is Ellipse)
        {
            MessageBox.Show("rectangle clicked!");
            var ellipse = ee as Ellipse;
            // Do something with ellipse
        }
        if(ee is Rectangle)
        {
            MessageBox.Show("ellipse clicked!");
            var rec = ee as Rectangle;
            // Do something with rectangle
        }

    }
}