[英]Why can't I paint a rectangle with this code in pictureBox?
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
namespace UTUResultWithCoordinates
{
public partial class GetCoordinates : Form
{
private string sem;
private string branch;
private int mouseisdown = 0;
private int recx = 0;
private int recy = 0;
private int mousemovingwhilepressed = 0;
public GetCoordinates()
{
InitializeComponent();
}
public GetCoordinates(string p, string p_2)
{
// TODO: Complete member initialization
InitializeComponent();
branch = p;
sem = p_2;
pictureBox1.Controls.Add(pictureBox2);
pictureBox2.Location = new Point(0, 0);
pictureBox2.BackColor = Color.Transparent;
pictureBox2.Width = 1191;
pictureBox2.Height = 842;
}
private void GetCoordinates_Load(object sender, EventArgs e)
{
pictureBox1.ImageLocation = @"D:\DotNet\UTUResultWithCoordinates\UTUResultWithCoordinates\bin\Debug\ComputerScience6.jpg";
}
private void pictureBox2_Paint(object sender, PaintEventArgs e)
{
if (mouseisdown == 1 && mousemovingwhilepressed==1)
{
System.Drawing.Graphics graphicsObj;
graphicsObj = this.CreateGraphics();
Pen myPen = new Pen(System.Drawing.Color.Blue, 100);
Rectangle myRectangle = new Rectangle(recx, recy, 20, 20);
e.Graphics.DrawRectangle(myPen, myRectangle);
}
}
private void pictureBox2_MouseDown(object sender, MouseEventArgs e)
{
mouseisdown = 1;
recx = e.X;
recy = e.Y;
pictureBox2.CreateGraphics();
}
private void pictureBox2_MouseMove(object sender, MouseEventArgs e)
{
label1.Text = e.X + "," + e.Y;
mousemovingwhilepressed = 1;
recx = e.X;
recy = e.Y;
pictureBox2.CreateGraphics();
}
private void pictureBox2_MouseUp(object sender, MouseEventArgs e)
{
mousemovingwhilepressed = 0;
mouseisdown = 0;
pictureBox2.CreateGraphics();
}
}
}
我已经创建了其中显示图像的pictureBox1。 然后,我在其中创建了一个pictureBox2,以便可以通过拖动鼠标在该图像上绘制一个矩形。 但是单击鼠标没有任何反应。 有什么错误?
调用CreateGraphics不会触发PictureBox的绘制。
使用Invalidate导致重画。
有关完整示例,请参见: 如何在C#中用鼠标选择PictureBox.Image上的区域。
旁注:
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.