移动折线 WPF

Question

我想为我所有的程序移动一个加号，并得到符号中心的点。加号是一个形状，它在 canvas:

<Canvas x:Name="canvas1" PreviewMouseLeftButtonDown="canvas1_PreviewMouseDown" 
        PreviewMouseMove="canvas1_PreviewMouseMove"
        PreviewMouseLeftButtonUp="canvas1_PreviewMouseUp" Grid.ColumnSpan="2" Margin="0,0,10,0">
        <Polyline Name="myPolyline"
          MouseDown="Polyline_MouseDown"
          Points="25,0 25,50 25,25 0,25 50,25" 
          Stroke="Blue"
          StrokeThickness="2"
          Height="50"/>
    </Canvas>

我的方法：

private void canvas1_PreviewMouseDown(object sender, MouseButtonEventArgs e)
    {
        //Check if the click was in a chape
        if (e.Source is Shape)
        {
            // Get the mouse position
            start = e.GetPosition(canvas1);
            // Initialize some components and set opacity to 50%
            isDragging = true;
            movedElement = (Shape)e.Source;
            ((Shape)e.Source).Opacity = 0.5;
            canvas1.CaptureMouse();
            e.Handled = true;
        }
    }

    private void canvas1_PreviewMouseMove(object sender, MouseEventArgs e)
    {
        if (isDragging)
        {
            Point Pt = e.GetPosition(canvas1);
            // Get the actual position of the Shape
            double CurrentLeft = (double)movedElement.GetValue(Canvas.LeftProperty);
            double CurrentTop = (double)movedElement.GetValue(Canvas.TopProperty);

            // Calc the new position
            double newLeft = CurrentLeft + Pt.X - start.X;
            double newTop = CurrentTop + Pt.Y - start.Y;

            // Move the element
            movedElement.SetValue(Canvas.LeftProperty, newLeft);
            movedElement.SetValue(Canvas.TopProperty, newTop);

            start = Pt;
            e.Handled = true;
        }
    }

    private void canvas1_PreviewMouseUp(object sender, MouseButtonEventArgs e)
    {
        // Restore the values
        movedElement.Opacity = 1;
        movedElement.SetValue(Canvas.ZIndexProperty, ++currentZ);
        isDragging = false;
        canvas1.ReleaseMouseCapture();
    }

我发现一些方法可以完美地移动直线、矩形和椭圆，但我的加号是折线，而这些方法并没有移动它，我相信原因在于直线：

movedElement = (Shape)e.Source; 或

double CurrentLeft = (double)movedElement.GetValue(Canvas.LeftProperty); double CurrentTop = (double)movedElement.GetValue(Canvas.TopProperty);

因为 GetValue 正在返回 "NaN" 而我真的不知道 why.I 尝试使用两行来制作加号，但我很难移动这两行 toguether.Can 有人告诉我代码中是否有错误或问题出在我的加号类型上吗？谢谢

Answer 1

您需要在 XAML 中初始化 Canvas.Left 和 Canvas.Top 属性，然后才能在代码隐藏中查询它们。默认情况下它们为空。示例：

<Polyline Name="myPolyline"
    ...
    Canvas.Left="0"
    Canvas.Top="0"
    />

Answer 2

强调文本

enter code here
    private void canvas2_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        //create polyline
        polyline1 = new Polyline();
        polyline1.StrokeThickness = 4;
        polyline1.Stroke = Brushes.Black;
        Canvas.SetTop(polyline1, 0);
        Canvas.SetLeft(polyline1, 0);
    }


    private bool isPolyLine1Drog;
    double mousePosOnPolyline1X;
    double mousePosOnPolyline1Y;
    private void Polyline1_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        isPolyLine1Drog = true;
        //get distance between current mouse position and top_left polyline
        mousePosOnPolyline1X= e.GetPosition(canvas2).X-Canvas.GetLeft(polyline1);
        mousePosOnPolyline1Y = e.GetPosition(canvas2).Y-Canvas.GetTop(polyline1);
        polyline1.CaptureMouse();
    }
    private void Polyline1_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
    {
        isPolyLine1Drog = false;
        polyline1.ReleaseMouseCapture();
    }
    private void Polyline1_MouseMove(object sender, MouseEventArgs e)
    {
        if (!isPolyLine1Drog) return;
        //top=top+Y changing and left=left+X changing
        double left= e.GetPosition(canvas2).X - mousePosOnPolyline1X;
        double top = e.GetPosition(canvas2).Y - mousePosOnPolyline1Y;
        Canvas.SetLeft(polyline1, left);
        Canvas.SetTop(polyline1, top);
    }//mohsen_seif@yahoo.com

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