相当于绘图应用程序的橡皮擦、c#、silverlight、wp7

发布于 2024-11-09 04:45:41 字数 577 浏览 0 评论 0原文

我正在开发一个简单的绘图应用程序，以进一步提高我的技能，但我似乎无法理解橡皮擦工具的逻辑。该应用程序仅使用 Line 类在用户移动手指时创建线条。对于橡皮擦工具，我尝试使用 VisualTreeHelper，如下所示：

List<UIElement> elements = (List<UIElement>)VisualTreeHelper.FindElementsInHostCoordinates(e.GetPosition(tree), ContentPanelCanvas);

            foreach (UIElement element in elements)
            {
                if (element is Line)
                {
                    this.ContentPanelCanvas.Children.Remove(element);
                }
            }

它在某些时候可能非常缓慢且滞后。有时我必须触摸该区域超过 5 次才能摆脱那里的线。

有替代方案吗？

原文

I'm working on a simple drawing app to further advance my skills and I can't seem to get the logic down for an eraser tool. The app simply uses the Line class to create lines as the user moves their finger. For the eraser tool I tried using the VisualTreeHelper as follows:

List<UIElement> elements = (List<UIElement>)VisualTreeHelper.FindElementsInHostCoordinates(e.GetPosition(tree), ContentPanelCanvas);

            foreach (UIElement element in elements)
            {
                if (element is Line)
                {
                    this.ContentPanelCanvas.Children.Remove(element);
                }
            }

It at some points but can be very slow and laggy. Sometimes I would have to touch the area more than 5 times to get rid of the line there.

Is there an alternative to this?

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莫相离 2024-11-16 04:45:41

e.GetPosition(tree) 将返回一个点。尝试使用以位置为中心的矩形。

const double fingerMargin = 10.0;

Point p = e.GetPosition(tree);
Rect r = new Rect(p.X - fingerMargin, p.Y - fingerMargin, fingerMargin * 2, fingerMargin * 2); 

var elements = VisualTreeHelper.FindElementsInHostCoordinates(r, ContentPanelCanvas);

Line lineToRemove = elements.OfType<Line>().FirstOrDefault();
if (lineToRemove != null)
{
    ContentPanelCanvas.Children.Remove(lineToRemove);
}

请注意，不要将 FindElementsInHostCooperatives 的结果强制转换为 List，这是一个实现细节，文档仅保证它是一个 IEnumerable，除此之外这是不必要的演员阵容。

The e.GetPosition(tree) will be returning a point. Try instead using a Rect with the position as its center.

const double fingerMargin = 10.0;

Point p = e.GetPosition(tree);
Rect r = new Rect(p.X - fingerMargin, p.Y - fingerMargin, fingerMargin * 2, fingerMargin * 2); 

var elements = VisualTreeHelper.FindElementsInHostCoordinates(r, ContentPanelCanvas);

Line lineToRemove = elements.OfType<Line>().FirstOrDefault();
if (lineToRemove != null)
{
    ContentPanelCanvas.Children.Remove(lineToRemove);
}

Note don't cast the result of FindElementsInHostCoordinates to List<T>, that is an implementation detail, the documentation only guarantees it to be an IEnumerable<UIElement>, besides which it is an unnecessary cast.

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