Question

c#程序没有错误，为什么在picturebox中显示不出来画的东西啊，是鼠标事件没有发挥作用吗？

private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
{
pictureBox1.Refresh();
Pen mypen = new Pen(Color.Red, 6);//画笔
Point pShebei = new Point(0, 0);
Graphics g = pictureBox1.CreateGraphics();//画图
Brush redBrush = Brushes.Red;
Font songti = new Font("宋体", 14);

startpoint.X = MousePosition.X - 270;
startpoint.Y = MousePosition.Y - 28;
int realheng = MousePosition.X - 270;
int realshu = MousePosition.Y - 28;
g.DrawString("" + "▼" + "", songti, redBrush, new Rectangle(new Point(startpoint.X - 4, startpoint.Y - 46), new Size(50, 50)));

Answer 1

鼠标事件起作用了。你没有看到那个“▼”的原因是：当pictureBox1刷新时，将画出的内容又“清空”了。改成这样的试试：

 //pictureBox1的Pain事件
 private void pictureBox1_Paint(object sender, PaintEventArgs e)
        {
            Pen mypen = new Pen(Color.Red, 6);//画笔
            Point pShebei = new Point(0, 0);
            //直接从事件参数e获取 Graphics
            Graphics g = e.Graphics;
            Brush redBrush = Brushes.Red;
            Font songti = new Font("宋体", 14);
            
            Point startpoint = new Point();
            startpoint.X = p.X - 270;
            startpoint.Y = p.Y - 28;
            int realheng = p.X - 270;
            int realshu = p.Y - 28;
            g.DrawString("" + "▼" + "", songti, redBrush, new Rectangle(new Point(startpoint.X - 4, startpoint.Y - 46), new Size(50, 50)));
        }

        Point p = Point.Empty; //记录鼠标的位置
        private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
        {
            p = MousePosition;
            //引发pictureBox1的Paint事件！
            pictureBox1.Invalidate();
        }

追问

能加个好友吗？交我编编程序啊，感觉毕不了业了。其实这个程序如果只有一个picturebox的时候可以画出来，但如果把picturebox放到tabcontrol或者旁边在picturebox左边加一个gradview又画不出来了 不知道什么情况

Answer 2

private Bitmap CreateImage()
{
Bitmap img=new Bitmap(this.pictureBox1.Width,this.pictureBox1.Height);
Graphics g = Graphics.FromImage(img);

Pen mypen = new Pen(Color.Red, 6);//画笔
Brush redBrush = Brushes.Red;
Font songti = new Font("宋体", 14);

Point mousepoint= MousePosition;
Point startpoint = new Point(0,0);
Point contorlpoint = PointToScreen(this.pictureBox1.Location);

startpoint.X = mousepoint.X - contorlpoint.X-14;
startpoint.Y = mousepoint.Y - contorlpoint.Y-7;
g.DrawString("" + "▼" + "", songti, redBrush, new Rectangle(startpoint, new Size(50, 50)));
return img;
}

private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
{
this.pictureBox1.Image = CreateImage();
this.pictureBox1.Refresh();
}

追问

你的能显示出来吗？ 我怎么还是显示不了啊

追答

你的是不是在panel里面写的 调试下就知道了，估计是没触发到pictureBox1_MouseDown事件，而是触发到了panel的MouseDown的事件了，解决办法有两个：一是放出来 不要把pictureBox1放在容器里，二是在放置pictureBox1的容器的MouseDown里面设置pictureBox1_MouseDown一样的内容。

Answer 3

你是想实现什么样的功能？

追问

就是鼠标点一下，在图片上显示那个倒三角符号