如何画使用MouseMove事件一行 [英] How to draw a single line using MouseMove Event

问题描述

我想提请使用的OnMouseMove（）事件一行。我的问题是，每次我把鼠标移动它留下痕迹。我试图用的刷新方法，但是当我停止移动鼠标线已经一去不复返了。我不想被绘制行的OnPaint（）; ，只希望它画的OnMouseMove（）。

I'm trying to draw a single line using OnMouseMove() event. My Problem is that everytime I move the mouse It leaves a trail. I tried to use the refresh method, but when I stop moving the mouse the line is gone. I don't want the line to be drawn OnPaint();, Just want to draw it OnMouseMove().

编辑：我使用的是透明面板（cp.ExStyle | = 0x20的），所以我不能使用 graphics.Clear（）和背景色（）

I'm using a transparent panel(cp.ExStyle |= 0x20;), so I cant use the graphics.Clear() and BackColor()

下面是一个示例图片没有刷新（）：

Here's a Sample Image without the Refresh():

下面是我的代码：

private void panel1_MouseMove(object sender, MouseEventArgs e)
{  
   Graphics g = panel1.CreateGraphics();

   g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
   using (var p = new Pen(Color.Black, 3))
   {
      p.StartCap = System.Drawing.Drawing2D.LineCap.ArrowAnchor;
      p.EndCap = System.Drawing.Drawing2D.LineCap.ArrowAnchor;

      g.DrawLine(p, st, e.Location);
   }
   Thread.Sleep(30);
   Invalidate();
   //this.Refresh();

   g.Dispose();
}

问候

Regards

推荐答案

我下面的作品。基本上跟踪的最后一行的绘制，绘制在它与面板的背景颜色（给清除它的影响）。

The following works for me. Basically keep track of the last line drawn and draw over it with the background color of the panel (gives the effect of clearing it).

   public partial class Form1 : Form
   {
      public Form1()
      {
         InitializeComponent();
      }

      private const int PEN_WIDTH = 3;
      private const LineCap START_CAP = LineCap.ArrowAnchor;
      private const LineCap END_CAP = LineCap.ArrowAnchor;
      Point mAnchorPoint = new Point(10, 10);
      Point mPreviousPoint = Point.Empty;

      private void panel1_MouseMove(object sender, MouseEventArgs e)
      {
         using (Graphics g = panel1.CreateGraphics())
         {
            // Clear last line drawn
            using (Pen clear_pen = new Pen(panel1.BackColor, PEN_WIDTH))
            {
               clear_pen.StartCap = START_CAP;
               clear_pen.EndCap = END_CAP;
               g.DrawLine(clear_pen, mAnchorPoint, mPreviousPoint);
            }

            // Update previous point
            mPreviousPoint = e.Location;

            // Draw the new line
            using (Pen draw_pen = new Pen(Color.Black, PEN_WIDTH))
            {
               draw_pen.StartCap = START_CAP;
               draw_pen.EndCap = END_CAP;
               g.DrawLine(draw_pen, mAnchorPoint, e.Location);
            }
         }
      }
   }

如果您面板的背景色设置为透明，你将需要更改 panel1.BackColor 到 panel1.Parent.BackColor

If you panel's background color is set to Transparent, you will need to change panel1.BackColor to panel1.Parent.BackColor

如果透明面板不工作，你可以使用 DrawReversibleLine 功能（虽然这并不让颜色或线路的厚度改变，应该没有问题与绘图/擦除即使面板是透明的：

If the Transparent Panel is not working, you could use the DrawReversibleLine function (although this doesn't allow the color or thickness of the line to be changed, it should have no issues with drawing/erasing even if the panel is Transparent:

  Point mAnchorPoint = new Point(200, 200);
  Point mPreviousPoint = Point.Empty;

  private void panel1_MouseMove(object sender, MouseEventArgs e)
  {
     if (mPreviousPoint != Point.Empty)
     {
        // Clear last line drawn
        ControlPaint.DrawReversibleLine(PointToScreen(mAnchorPoint), PointToScreen(mPreviousPoint), Color.Pink);
     }

     // Update previous point
     mPreviousPoint = e.Location;
     mPreviousPoint.Offset(myPanel1.Location);

     // Draw the new line
     ControlPaint.DrawReversibleLine(PointToScreen(mAnchorPoint), PointToScreen(mPreviousPoint), Color.Pink);
  }

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