winfrom-拖动鼠标绘制矩形

╰半夏微凉° 2022-07-12 02:11 235阅读 0赞

using System;
    using System.Collections.Generic;
    using System.Drawing;
    using System.Windows.Forms;
    
    namespace WindowsFormsApplication2
    {
        //http://bbs.csdn.net/topics/390567044
        //http://heisetoufa.iteye.com/blog/380977
        //http://blog.csdn.net/xuyongbeijing2008/article/details/17371311
    
        public partial class Form2 : Form
        {
            bool bDrawStart = false;
            Point pointStart = Point.Empty;
            Point pointContinue = Point.Empty;
            Dictionary<Point, Point> dicPoints;
    
            public Form2()
            {
                InitializeComponent();
    
                dicPoints = new Dictionary<Point, Point>();
                DoubleBuffered = true;
                this.SetStyle(ControlStyles.AllPaintingInWmPaint | ControlStyles.OptimizedDoubleBuffer | ControlStyles.UserPaint, true);
    
                this.MouseDown += new MouseEventHandler(frmMain_MouseDown);
                this.MouseMove += new MouseEventHandler(frmMain_MouseMove);
                this.MouseUp += new MouseEventHandler(frmMain_MouseUp);
                this.Paint += new PaintEventHandler(frmMain_Paint);
            }
    
            private void frmMain_Paint(object sender, PaintEventArgs e)
            {
                Pen pen = new Pen(Color.Black, 1f);
                pen.DashStyle = System.Drawing.Drawing2D.DashStyle.Dash;
                
                if (bDrawStart)
                {
                    //实时的画矩形
                    int w = pointContinue.X - pointStart.X;
                    int h = pointContinue.Y - pointStart.Y;
                    Rectangle rect = new Rectangle(pointStart, new Size(w, h));
                    e.Graphics.DrawRectangle(pen, rect);
                }
                pen.Dispose();
            }
    
            void frmMain_MouseDown(object sender, MouseEventArgs e)
            {
                if (bDrawStart)
                {
                    bDrawStart = false;
                }
                else
                {
                    bDrawStart = true;
                    pointStart = e.Location;
                }
            }
            void frmMain_MouseMove(object sender, MouseEventArgs e)
            {
                if (bDrawStart)
                {
                    pointContinue = e.Location;
                    //Refresh();
                    Invalidate();
                }
            }
            void frmMain_MouseUp(object sender, MouseEventArgs e)
            {
                if (bDrawStart)
                {
                    dicPoints.Add(pointStart, pointContinue);
                }
                bDrawStart = false;
            }
    
            //...
    
        }
    }

![SouthEast][]

[SouthEast]: /images/20220711/75c2d513aa7c4207b23528fc2cf7fec1.png