代码之家 › 专栏 › 技术社区 › Ace

实时绘制到下一点的直线

line drawing wpf c#

Ace · 技术社区 · 12 年前

我当前的程序允许用户单击一个点,然后单击另一个点(至少20个像素),并在这两个点之间画一条线。我使用了一条多段线,这样就可以多次执行。尽管所有线条的集合只有在完成所有单击之后才会出现。

void DrawingCanvas_MouseUp(object sender, MouseButtonEventArgs e) {
        Point position = e.GetPosition(this);

        if (leftList == null) {
            //starting a new set
            leftList.Add(position);
            lastPoint = position;
            return;
        }
        //calculate distance, i.e. end click
        double a = lastPoint.X - position.X;
        double b = lastPoint.Y - position.Y;
        double distance = Math.Sqrt(a * a + b * b);
        if (distance > 20) {
            //continue to add to list
            leftList.Add(position);
            lastPoint = position;
        } else {
            //end of the line
            paint();
            leftList = new PointCollection(); 
        }

    }

    private void paint() {
        Polyline line = new Polyline();
        line.Visibility = System.Windows.Visibility.Visible;
        line.StrokeThickness = 2;
        line.Stroke = System.Windows.Media.Brushes.Black;
        line.Points = leftList;
        myCanvas.Children.Add(line);
    }

所以我的问题有两个:

A) 我如何做到每次点击后都会立即添加新行。

B) 如何渲染上一点和鼠标光标当前所在位置之间的线(即,在选择下一点之前)

2 回复 | 直到 12 年前

Clemens 12 年前

以下简单示例在按住鼠标左键并将鼠标移动最小点距离20的同时开始绘制新的多段线。它以红色或绿色绘制最后一条多段线线段(到当前鼠标位置),具体取决于其长度。如果释放鼠标按钮,并且新线段的长度为>=20,一个新的点被附加到多段线。否则,多段线将终止,并且可以创建新的多段线。

private Polyline polyline;
private Polyline segment = new Polyline { StrokeThickness = 2 };

private void Canvas_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
    if (polyline == null)
    {
        var canvas = (Canvas)sender;
        var point = e.GetPosition(canvas);

        // create new polyline
        polyline = new Polyline { Stroke = Brushes.Black, StrokeThickness = 2 };
        polyline.Points.Add(point);
        canvas.Children.Add(polyline);

        // initialize current polyline segment
        segment.Stroke = Brushes.Red;
        segment.Points.Add(point);
        segment.Points.Add(point);
        canvas.Children.Add(segment);
    }
}

private void Canvas_MouseMove(object sender, MouseEventArgs e)
{
    if (polyline != null)
    {
        // update current polyline segment
        var canvas = (Canvas)sender;
        segment.Points[1] = e.GetPosition(canvas);

        var distance = (segment.Points[0] - segment.Points[1]).Length;
        segment.Stroke = distance >= 20 ? Brushes.Green : Brushes.Red;
    }
}

private void Canvas_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
    if (polyline != null)
    {
        var canvas = (Canvas)sender;
        segment.Points[1] = e.GetPosition(canvas);

        var distance = (segment.Points[0] - segment.Points[1]).Length;

        if (distance >= 20)
        {
            polyline.Points.Add(segment.Points[1]);
            segment.Points[0] = segment.Points[1];
        }
        else
        {
            if (polyline.Points.Count < 2)
            {
                canvas.Children.Remove(polyline);
            }

            polyline = null;
            segment.Points.Clear();
            canvas.Children.Remove(segment);
        }
    }
}

Shafqat Masood 12 年前

请在每次点击时保留一个积分集合。在集合中,您可以添加一个类,该类将具有StartPoint和EndPoint等两个属性。

当第一次单击鼠标时,只需将一个类对象添加到只有起点的集合中。当您下次单击鼠标时,将端点标记到类的最后一个对象,同时创建一个新对象,并将该点指定为其起点并将其添加到集合中,然后调用paint函数。