如何重画Windows控件

例1：改变控件属性

使用Visual Studio .NET来开发软件时，可以利用其强大的IDE环境来手工设定界面控件的属性。但是如果你要使你整个程序上的控件风格都是某种特定属性的话，那最好的方法就是自己重载控件类。

让我们从最简单的System.Windows.Forms.Button类开始尝试，按钮有如下的常用属性：

BackColor--按钮的背景颜色

Cursor--鼠标状态

Enabled--是否启用按钮

FlatStyle--按钮的扁平风格

Font--按钮上的字体

ForeColor--按钮的前景颜色

Height--按钮的高度

Image--按钮上的图片

Location--按钮上的位置

Text--按钮上的文字

Visible--按钮是否可见

Width--按钮的宽度

在下面的这个例子里面，我们得到一个蓝底白字的扁平按钮：

1、在Visual C# .NET中新建一个Windows Application项目，命名为OwnDrawButton1；

2、往项目中添加一个MyButton类，将其改为继承System.Windows.Forms.Button，并在构造函数中添加修改属性的代码；

就像这样：

public class MyButton : System.Windows.Forms.Button
{
public MyButton()
{
//set the back color to blue
BackColor = System.Drawing.Color.Blue;
//set the appearance style to flat
FlatStyle = System.Windows.Forms.FlatStyle.Flat;
//use system default font
Font = System.Windows.Forms.Control.DefaultFont;
//use white color to write text and draw the border
ForeColor = System.Drawing.Color.White;
}
}

3、拖一个按钮到Form1上，右击鼠标，单击"View Code"，在代码中用"MyButton"替换掉"System.Windows.Forms.Button"；

4、编译执行。

现在，你就能在你的界面上看到自定义的控件了（如图1）。

图1 通过代码修改控件属性的按钮

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例2：重画简单控件

仅通过改变控件的属性值来自定义控件，在很多情况下是不能令人满意的。例如如果想把Windows XP里那种风格的按钮放到Windows 98/2000下，你就得自己来画那些按钮了。

在这种情况下，你可以通过重载OnPaint()等事件来重画按钮。你也可以通过EventHandler来让控件响应更多的事件，例如，我们可以给按钮添加鼠标悬停效果，给MouseEnter和MouseLeave分别加上EeventHandler，这样，你在事件响应函数里写的代码就会被调用。

下面是一个例子，这个例子编写了一个类似Windows XP中按钮风格的控件：

1、在Visual C# .NET中新建一个Windows Application项目，命名为OwnDrawButton2；

2、往项目中添加一个MyButton类，将其改为继承System.Windows.Forms.Button，在构造函数中添加修改属性的代码和事件响应关联代码，并编写各函数代码，如下所列：

using System;
using System.Drawing;
using System.Windows;
using System.Windows.Forms;
namespace OwnDrawButton2
{
public class MyButton : System.Windows.Forms.Button
{
//state variable for mouse down
private bool mouseDown=false;
//state variable for mouse hover
private bool mouseHover=false;
public MyButton()
{
//set the control UserPaint
SetStyle(ControlStyles.UserPaint,true);
//EventHandler for MouseDown
MouseDown+=new MouseEventHandler(OnMouseDown);
//EventHandler for MouseUp
MouseUp+=new MouseEventHandler(OnMouseUp);
//EventHandler for MouseEnter
MouseEnter+=new EventHandler(OnMouseEnter);
//EventHandler for MouseLeave
MouseLeave+=new EventHandler(OnMouseLeave);
Height=23;//Default Height
Width=75;//Default Width
}
protected override void OnPaint(PaintEventArgs pe)
{
//first, paint the control with parent form's background color
pe.Graphics.FillRectangle(new SolidBrush(Parent.BackColor),
pe.ClipRectangle);
//if the button is disabled, draw the disable style
if (Enabled == false)
{
DrawDisableButton(pe.Graphics);
}
else if (mouseDown)
{
//when mouse down, draw the mouse down style
DrawMouseDownButton(pe.Graphics);
}
else if (mouseHover)
{
//when mouse hover, draw the mouse hover style
DrawMouseHoverButton(pe.Graphics);
}
else if (Focused)
{
//when mouse is focused but not mouse hover,
//draw the focus style
DrawContainFocusButton(pe.Graphics);
}
else//else, draw the normal style
{
DrawNormalButton(pe.Graphics);
}
WriteText(pe.Graphics);//write text
}
private void OnMouseDown(object sender,MouseEventArgs e)
{
mouseDown=true;	//mouse is down now
}
private void OnMouseUp(object sender,MouseEventArgs e)
{
mouseDown=false;	//mouse is up now
//call paint action
PaintEventArgs pe =
new PaintEventArgs(CreateGraphics(),ClientRectangle);
OnPaint(pe);
}
private void OnMouseEnter(object sender,EventArgs e)
{
mouseHover=true;	//mouse hover on
//call paint action
PaintEventArgs pe =
new PaintEventArgs(CreateGraphics(),ClientRectangle);
OnPaint(pe);
}
private void OnMouseLeave(object sender,EventArgs e)
{
mouseHover=false;	//mouse is not hover on
//call paint action
PaintEventArgs pe =
new PaintEventArgs(CreateGraphics(),ClientRectangle);
OnPaint(pe);
}
private void DrawBorder(Graphics g,int state)
{
if (state==1)//draw normal style broder
{
Pen p = new Pen(SystemColors.ControlLightLight,2);
g.DrawLine(p,1,1,1,Height-2);
g.DrawLine(p,1,1,Width-2,1);
g.DrawLine(p,Width-1,2,Width-1,Height-2);
g.DrawLine(p,2,Height-1,Width-2,Height-1);
}
else if (state==2)//draw hover style border
{
Pen p = new Pen(Color.Yellow,2);
g.DrawLine(p,1,1,1,Height-2);
g.DrawLine(p,1,1,Width-2,1);
g.DrawLine(p,Width-1,2,Width-1,Height-2);
g.DrawLine(p,2,Height-1,Width-2,Height-1);
}
else if (state==3)//draw pressed style border
{
Pen p = new Pen(SystemColors.ControlDark,2);
g.DrawLine(p,1,1,1,Height-2);
g.DrawLine(p,1,1,Width-2,1);
g.DrawLine(p,Width-1,2,Width-1,Height-2);
g.DrawLine(p,2,Height-1,Width-2,Height-1);
}
else if (state==4)//draw disabled style border
{
Pen p = new Pen(SystemColors.ControlLight,2);
g.DrawLine(p,1,1,1,Height-2);
g.DrawLine(p,1,1,Width-2,1);
g.DrawLine(p,Width-1,2,Width-1,Height-2);
g.DrawLine(p,2,Height-1,Width-2,Height-1);
}
else if (state==5)//draw default style border
{
Pen p = new Pen(Color.SkyBlue,2);
g.DrawLine(p,1,1,1,Height-2);
g.DrawLine(p,1,1,Width-2,1);
g.DrawLine(p,Width-1,2,Width-1,Height-2);
g.DrawLine(p,2,Height-1,Width-2,Height-1);
}
if (state==4)//draw disable style border
{
Pen p = new Pen(Color.FromArgb(161,161,146),1);
g.DrawLine(p,0,2,0,Height-3);
g.DrawLine(p,2,0,Width-3,0);
g.DrawLine(p,Width-1,2,Width-1,Height-3);
g.DrawLine(p,2,Height-1,Width-3,Height-1);
g.DrawLine(p,0,2,2,0);
g.DrawLine(p,0,Height-3,2,Height-1);
g.DrawLine(p,Width-3,0,Width-1,2);
g.DrawLine(p,Width-3,Height-1,Width-1,Height-3);
}
else//draw normal style border
{
g.DrawLine(Pens.Black,0,2,0,Height-3);
g.DrawLine(Pens.Black,2,0,Width-3,0);
g.DrawLine(Pens.Black,Width-1,2,Width-1,Height-3);
g.DrawLine(Pens.Black,2,Height-1,Width-3,Height-1);
g.DrawLine(Pens.Black,0,2,2,0);
g.DrawLine(Pens.Black,0,Height-3,2,Height-1);
g.DrawLine(Pens.Black,Width-3,0,Width-1,2);
g.DrawLine(Pens.Black,Width-3,Height-1,
Width-1,Height-3);
}
}
private void DrawNormalButton(Graphics g)//draw normal style button
{
//draw normal style border
DrawBorder(g,1);
//paint background
PaintBack(g,SystemColors.ControlLightLight);
}
private void DrawMouseHoverButton(Graphics g)
{
//draw mouse hover style border
DrawBorder(g,2);
//paint background
PaintBack(g,SystemColors.ControlLightLight);
}
private void DrawMouseDownButton(Graphics g)
{
//draw mouse down style border
DrawBorder(g,3);
//paint background
PaintBack(g,SystemColors.ControlLight);
}
private void DrawDisableButton(Graphics g)
{
//draw disable style border
DrawBorder(g,4);
//paint background
PaintBack(g,SystemColors.ControlLight);
}
private void DrawContainFocusButton(Graphics g)
{
//draw contain focuse style border
DrawBorder(g,5);
//paint background
PaintBack(g,SystemColors.ControlLightLight);
}
//paint background area of the button
private void PaintBack(Graphics g,Color c)
{
g.FillRectangle(new SolidBrush(c),3,3,
Width-6,Height-6);
}
private void WriteText(Graphics g)
{
//calculate the text position
int x=0,y=0;
Size s = g.MeasureString(Text,Font).ToSize();
x=(Width-s.Width)/2;
y=(Height-s.Height)/2;
//draw text
if (Enabled) //is enabled, draw black text
g.DrawString(Text,Font,Brushes.Black,x,y);
else //not enabled, draw gray text
g.DrawString(Text,Font,Brushes.Gray,x,y);
}
}
}

3、在新控件的构造函数中添加：拖3个按钮到Form1上，将其中一个的"Enable"设为"false"，右击鼠标，单击"View Code"，在代码中用"MyButton"替换掉"System.Windows.Forms.Button"；

4、编译执行。

最终，我们就得到了如图2所示的按钮控件。它可以在任何版本的windows操作系统上都保持一个样子。

图2 一个类似于Windows XP样式的按钮控件