wpf 使用 MouseMove 事件在画布内移动动态绘制的矩形

Moving the dynamically drawn rectangle inside the canvas using MouseMove event

提问by Jay

I'm trying to move a dynamically drawn rectangle inside the canvas. I'm able to draw the rectangle dynamically with in the canvas and while trying to move the rectangle inside the canvas I'm facing problem

我正在尝试在画布内移动一个动态绘制的矩形。我能够在画布中动态绘制矩形，同时尝试在画布内移动矩形我遇到了问题

XAML :

XAML：

   <Grid x:Name="Gridimage1" Margin="0,0,411,100">
      <Image Name="image1" HorizontalAlignment="Left" Stretch="Fill" VerticalAlignment="Top"></Image>
        <Canvas x:Name="BackPanel" Margin="20,67,0,0" Height="317" Width="331">
           <Rectangle x:Name="selectionRectangle" Stroke="LightBlue" Fill="#220000FF"/>
        </Canvas>
   </Grid>

C# :

C＃ ：

After drawing the rectangle dynamically I'm adding the below mouse events.

动态绘制矩形后，我添加了以下鼠标事件。

selectionRectangle.MouseLeftButtonDown += new MouseButtonEventHandler(Rect1_MouseDown);
selectionRectangle.MouseMove += new MouseEventHandler(Rectangle_MouseMove_1);
selectionRectangle.MouseUp += new MouseButtonEventHandler(Rect1_MouseUp); 
     # region "rectangle move"
    private bool drag = false;
    private Point startPt;
    private int wid;
    private int hei;
    private Point lastLoc;
    private double CanvasLeft, CanvasTop;
    private void Rect1_MouseDown(object sender, MouseButtonEventArgs e)
    {
        drag = true;
        Cursor = Cursors.Hand;
        startPt = e.GetPosition(BackPanel);
        wid = (int)selectionRectangle.Width;
        hei = (int)selectionRectangle.Height;
        lastLoc = new Point(Canvas.GetLeft(selectionRectangle), Canvas.GetTop(selectionRectangle));
       Mouse.Capture((IInputElement)sender);
    }

    private void Rectangle_MouseMove_1(object sender, MouseEventArgs e)
    {
        try
        {
            if (drag)
            {
                    var newX = (startPt.X + (e.GetPosition(BackPanel).X - startPt.X));
                    var newY = (startPt.Y + (e.GetPosition(BackPanel).Y - startPt.Y));
                    Point offset = new Point((startPt.X - lastLoc.X), (startPt.Y - lastLoc.Y));
                    CanvasTop = newY - offset.Y;
                    CanvasLeft = newX - offset.X;
                    selectionRectangle.SetValue(Canvas.TopProperty, CanvasTop);
                    selectionRectangle.SetValue(Canvas.LeftProperty, CanvasLeft);               

            }
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);    
        }

    }
    private void Rect1_MouseUp(object sender, MouseButtonEventArgs e)
    {
        drag = false;
        Cursor = Cursors.Arrow;
        Mouse.Capture(null);
    }
    #endregion

Problem:I'm able to move the rectangle all over the window. I want only to move the rectangle inside the canvas margin.

问题：我可以在整个窗口中移动矩形。我只想在画布边距内移动矩形。

I'm able to move the rectangle outside the canvas

我可以将矩形移动到画布外

回答by Chris Badman

You should be able to get the Boundsof your selectionRectangle and see if they exceed the Widthand/or Heightof your canvas before committing the drag operation.

在提交拖动操作之前，您应该能够获得selectionRectangle的边界并查看它们是否超过画布的宽度和/或高度。

selectionRectangle.MouseMove += new MouseEventHandler(Rectangle_MouseMove_1);

private bool drag = false;
private Point startPt;
private int wid;
private int hei;
private Point lastLoc;
private double CanvasLeft, CanvasTop;

private void Rectangle_MouseMove_1(object sender, MouseEventArgs e)
{
    try
    {
        if (drag)
        {
                var newX = (startPt.X + (e.GetPosition(BackPanel).X - startPt.X));
                var newY = (startPt.Y + (e.GetPosition(BackPanel).Y - startPt.Y));
                Point offset = new Point((startPt.X - lastLoc.X), (startPt.Y - lastLoc.Y));
                CanvasTop = newY - offset.Y;
                CanvasLeft = newX - offset.X;

                // check if the drag will pull the rectangle outside of it's host canvas before performing
                // TODO: protect against lower limits too...
               if ((CanvasTop + selectionRectangle.Height > BackPanel.Height) || (CanvasLeft + selectionRectangle.Width > BackPanel.Width) || CanvasTop < 0 || CanvasLeft < 0)
                    {
                        return;
                    }
                selectionRectangle.SetValue(Canvas.TopProperty, CanvasTop);
                selectionRectangle.SetValue(Canvas.LeftProperty, CanvasLeft);               

        }
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.Message);    
    }

}

回答by Son0nline

if ((CanvasTop + selectionRectangle.ActualHeight > BackPanel.ActualHeight))
{
    CanvasTop = BackPanel.ActualHeight - selectionRectangle.ActualHeight;
}

if (CanvasLeft + selectionRectangle.ActualWidth > BackPanel.ActualWidth)
{
    CanvasLeft = BackPanel.ActualWidth - selectionRectangle.ActualWidth;
}

if (CanvasTop < 0)
{
    CanvasTop = 0;
}

if (CanvasLeft < 0)
{
    CanvasLeft = 0;
}