Question

c# 如何在panel上绘图？？

下面给出代码，请高手帮忙看看是哪里出错了？？非常感谢啊。
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Drawing.Drawing2D;
namespace WindowsApplication1.els
{
public partial class els : Form
{
public Color[] mycolor = new Color[] { Color.Black, Color.Brown };
public Point mypoint;
public Pen mypen = new Pen(Brushes.Black);
public els()
{
InitializeComponent();
draw();
}
void draw()
{
Graphics g =this.panelEx1.CreateGraphics();
GraphicsPath gp = new GraphicsPath();
Rectangle rec = new Rectangle(new Point(30, 30), new Size(100, 30));
gp.AddRectangle(rec);
PathGradientBrush pb = new PathGradientBrush(gp);
pb.CenterColor = Color.Blue;
pb.SurroundColors = mycolor;
g.DrawRectangle(mypen, rec);
g.FillPath(pb, gp);
}
}
}

Answer 1

由于Panel采用系统支持的绘图模式, 所以你直接在上面绘图很有可能被系统重绘覆盖. 我帮你修改了绘图函数, 在Panel的BackGroundImage上绘图, 见代码:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Drawing.Drawing2D;
namespace WindowsApplication1.els
{
public partial class els : Form
{
public Color[] mycolor = new Color[] { Color.Black, Color.Brown };
public Point mypoint;
public Pen mypen = new Pen(Brushes.Black);
public els()
{
InitializeComponent();
draw();
}
void draw() //修改的绘图函数
{
Image im = new Bitmap(this.panelEx1.Width, this.panelEx1.Height);
Graphics g = Graphics.FromImage(im);

GraphicsPath gp = new GraphicsPath();
Rectangle rec = new Rectangle(new Point(30, 30), new Size(100, 30));
gp.AddRectangle(rec);
PathGradientBrush pb = new PathGradientBrush(gp);
pb.CenterColor = Color.Blue;
pb.SurroundColors = mycolor;
g.DrawRectangle(mypen, rec);
g.FillPath(pb, gp);

this.panelEx1.BackgroundImageLayout = ImageLayout.Stretch;
this.panelEx1.BackgroundImage = im;
}
}
}

已经调试通过, 希望对你有帮助.

Answer 2

代码编译没错。
只不过不知道你想要的效果是怎么样的，是要点击控件激发事件，还是你想一运行程序就绘制出图形？

我试了下，在按钮事件中添加draw()方法，可以绘制出图形；但是我在Form_Load事件中添加draw()方法，却不能一运行程序就绘制出图形，这个问题我也是在困惑当中。

Answer 3

给个邮箱啊，不然怎么发你