保留一个元素并在绘图控件上绘制时刷新另一个元素？

Question

我想在一个图片框上画一条连续的线，也想在光标处画一个十字。如何只在鼠标位置绘制光标（并在下次移动时清除它）并保留线？

Answer 1

这只是为了让您了解如何处理这个......

将PictureBox添加到表单。运行它并在PictureBox中单击并拖动：

public partial class Form1 : Form
{

    Point cursor;
    Point lastPoint;
    System.Drawing.Drawing2D.GraphicsPath curPath = null;
    private List<System.Drawing.Drawing2D.GraphicsPath> paths = new List<System.Drawing.Drawing2D.GraphicsPath>();

    public Form1()
    {
        InitializeComponent();
        pictureBox1.MouseDown += new MouseEventHandler(pictureBox1_MouseDown);
        pictureBox1.MouseMove += new MouseEventHandler(pictureBox1_MouseMove);
        pictureBox1.Paint += new PaintEventHandler(pictureBox1_Paint);
    }

    void pictureBox1_Paint(object sender, PaintEventArgs e)
    {
        foreach (System.Drawing.Drawing2D.GraphicsPath gp in paths)
        {
            e.Graphics.DrawPath(Pens.Red, gp);
        }

        e.Graphics.DrawLine(Pens.Black, new Point(cursor.X, 0), new Point(cursor.X, pictureBox1.Height));
        e.Graphics.DrawLine(Pens.Black, new Point(0, cursor.Y), new Point(pictureBox1.Width, cursor.Y));
    }

    void pictureBox1_MouseDown(object sender, MouseEventArgs e)
    {
        if (e.Button == System.Windows.Forms.MouseButtons.Left)
        {
            lastPoint = new Point(e.X, e.Y);
            curPath = new System.Drawing.Drawing2D.GraphicsPath();
            paths.Add(curPath);
        }
    }

    void pictureBox1_MouseMove(object sender, MouseEventArgs e)
    {
        cursor = new Point(e.X, e.Y);

        if (e.Button == System.Windows.Forms.MouseButtons.Left)
        {
            Point newPoint = new Point(e.X, e.Y);
            curPath.AddLine(lastPoint, newPoint);
            lastPoint = newPoint;
            pictureBox1.Refresh();
        }

        pictureBox1.Refresh();
    }

}