什么是VB进行子类化及简单介绍

目录

• 何谓子类化（subclassing）
• Visual Basic 6子类化的实现
• Visual Basic .NET子类化的实现
• 小结

1. 何谓子类化（subclassing） 

　　众所周知，Windows是一个基于消息的系统，消息在Windows的对象之间进行着传递。子类化和Windows的钩子机制存在于消息系统之中，我们可以利用这些机制来操纵、修改甚至丢弃那些在操作系统或是进程中传递的消息，以求改变系统的一些行为。子类化技术用来截取窗口或控件之间的消息，当然是消息在到达目的窗口之前完成的操作。这些被截获的消息既可以保留也可以修改它们的状态，之后就继续发送到目的地。子类化技术实现了一些正常情况下无法实现的功能，试想鼠标右键单击TextBox，系统默认弹出Undo、Cut、Copy、Paste等菜单，我们就可以利用子类化技术来改变这个系统菜单。 

　　简单的说，子类化就是创建一个新的窗口消息处理过程，并将其插入到原先的默认窗口消息处理过程之前。 

　　子类化分为三类：实例子类化（instance subclassing）—从窗口或控件的单一实例截获消息，这种子类化技术最普遍；全局子类化（global subclassing）—能够截获从相同的窗口类创建出来的多个窗口或控件的消息；超类化（superclassing）—和全局子类化很类似，区别在于可以应用在新的窗口类上面。 

2. Visual Basic 6子类化的实现 

　　在Visual Basic 6子类化的实现中我将通过一段代码的实例来介绍这一技术在VB6中的应用。现在很多开发社区中经常谈到的一个话题就是界面开发如何Skin，这种技术有很多解决方式，如使用可以贴图的控件或使用第三方开发的换肤ActiveX控件。其实Skin技术需要处理的是WM_DRAWITEM、WM_MEASUREITEM、WM_NCPAINT消息，这些消息的主要用途就是可以重画控件和窗口的非客户区。想要对这些VB6无法处理的消息进行编程就必须用到子类化，这些消息都会被发送到能够自绘的控件的窗口上，因此下面的例子就是利用窗口子类化来重画Button控件。 

①创建工程 

　　启动Visual Basic 6同时创建一个标准EXE工程。 

②窗口布局 

　　在FORM1上放置3个Button控件，并将前两个Button的Style属性设置为1-Graphical，因为只有Style属性设置为Graphical的Button才可以Owner-drawn。 

③在窗体中录入代码

代码Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->Private Sub Command3_Click() '通过Enabled属性的控制，来显示重画控件在Unenabled状态时的效果 If Command1.Enabled Then Command1.Enabled = False Else Command1.Enabled = True End If End Sub Private Sub Form_Load() '安装子类化入口 Call Init(Me.hWnd) End Sub Private Sub Form_Unload(Cancel As Integer) '卸载子类化 Call Terminate(Me.hWnd) End Sub④加入一个模块并录入代码 Option Explicit' -- 引用Win32Api –'得到默认的窗口消息处理过程的地址需要的APIPrivate Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" (ByVal hWnd As Long, ByVal nIndex As Long) As Long'设置一个新的窗口消息处理过程的地址需要的APIPrivate Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hWnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long'给指定的窗口消息处理过程传递消息需要的APIPrivate Declare Function CallWindowProc Lib "user32" Alias "CallWindowProcA" (ByVal lpPrevWndFunc As Long, ByVal hWnd As Long, ByVal Msg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long'内存拷贝Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (Destination As Any, Source As Any, ByVal Length As Long)Const GWL_WNDPROC = (-4&)Dim PrevWndProc&Private Const WM_DESTROY = &H2Private Const WM_DRAWITEM = &H2BPrivate Type RECT Left As Long  Top As Long  Right As Long  Bottom As LongEnd Type'WM_DRAWITEM需要处理的结构体Private Type DRAWITEMSTRUCTCtlType As LongCtlID As LongitemID As LongitemAction As LongitemState As LonghwndItem As Longhdc As LongrcItem As RECTitemData As LongEnd Type' Owner draw 常量Private Const ODT_BUTTON = 4' Owner draw 动作Private Const ODA_DRAWENTIRE = &H1Private Const ODA_SELECT = &H2Private Const ODA_FOCUS = &H4' Owner draw 状态Private Const ODS_SELECTED = &H1Private Const ODS_GRAYED = &H2Private Const ODS_DISABLED = &H4Private Const ODS_CHECKED = &H8Private Const ODS_FOCUS = &H10'得到指定窗口的文本Private Declare Function GetWindowText Lib "user32" Alias "GetWindowTextA" (ByVal hWnd As Long, ByVal lpString As String, ByVal cch As Long) As Long'GDI相关API函数，重画Button时使用Private Declare Function SelectObject Lib "gdi32" (ByVal hdc As Long, ByVal hObject As Long) As LongPrivate Declare Function CreateSolidBrush Lib "gdi32" (ByVal crColor As Long) As LongPrivate Declare Function DeleteObject Lib "gdi32" (ByVal hObject As Long) As LongPrivate Declare Function GetSysColor Lib "user32" (ByVal nIndex As Long) As Long'色彩常量Const COLOR_SCROLLBAR = 0Const COLOR_BACKGROUND = 1Const COLOR_ACTIVECAPTION = 2Const COLOR_INACTIVECAPTION = 3Const COLOR_MENU = 4Const COLOR_WINDOW = 5Const COLOR_WINDOWFRAME = 6Const COLOR_MENUTEXT = 7Const COLOR_WINDOWTEXT = 8Const COLOR_CAPTIONTEXT = 9Const COLOR_ACTIVEBORDER = 10Const COLOR_INACTIVEBORDER = 11Const COLOR_APPWORKSPACE = 12Const COLOR_HIGHLIGHT = 13Const COLOR_HIGHLIGHTTEXT = 14Const COLOR_BTNFACE = 15Const COLOR_BTNSHADOW = 16Const COLOR_GRAYTEXT = 17Const COLOR_BTNTEXT = 18Const COLOR_INACTIVECAPTIONTEXT = 19Const COLOR_BTNHIGHLIGHT = 20Private Declare Function FillRect Lib "user32" (ByVal hdc As Long, lpRect As RECT, ByVal hBrush As Long) As LongPrivate Declare Function FrameRect Lib "user32" (ByVal hdc As Long, lpRect As RECT, ByVal hBrush As Long) As LongPrivate Declare Function CreatePen Lib "gdi32" (ByVal nPenStyle As Long, ByVal nWidth As Long, ByVal crColor As Long) As Long'画笔格式Const PS_SOLID = 0Const PS_DASH = 1 ' -------Const PS_DOT = 2 ' .......Const PS_DASHDOT = 3 ' _._._._Const PS_DASHDOTDOT = 4 ' _.._.._Const PS_NULL = 5Const PS_INSIDEFRAME = 6Const PS_USERSTYLE = 7Const PS_ALTERNATE = 8Const PS_STYLE_MASK = &HFPrivate Declare Function MoveToEx Lib "gdi32" (ByVal hdc As Long, ByVal x As Long, ByVal y As Long, lpPoint As POINTAPI) As LongPrivate Declare Function LineTo Lib "gdi32" (ByVal hdc As Long, ByVal x As Long, ByVal y As Long) As LongPrivate Type POINTAPI x As Long  y As LongEnd TypePrivate Declare Function DrawText Lib "user32" Alias "DrawTextA" (ByVal hdc As Long, ByVal lpStr As String, ByVal nCount As Long, lpRect As RECT, ByVal wFormat As Long) As LongPrivate Const DT_SINGLELINE = &H20Private Const DT_CENTER = &H1Private Const DT_VCENTER = &H4Private Declare Function SetTextColor Lib "gdi32" (ByVal hdc As Long, ByVal crColor As Long) As LongPrivate Declare Function SetBkMode Lib "gdi32" (ByVal hdc As Long, ByVal nBkMode As Long) As LongPrivate Const TRANSPARENT = 1' – 声明结束 --Private Sub DrawButton(ByVal hWnd As Long, ByVal hdc As Long, rct As RECT, ByVal nState As Long) Dim P As POINTAPI  Dim s As String  Dim hbr As Long  Dim hpen As Long    hbr = CreateSolidBrush(GetSysColor(COLOR_BTNFACE)) 'RGB(231, 231, 231)  SelectObject hdc, hbr  FillRect hdc, rct, hbr  DeleteObject hbr    '画文字时背景为透明状  SetBkMode hdc, TRANSPARENT  '得到Button的Caption  s = String$(255, " ")  GetWindowText hWnd, s, 255  s = Trim$(s)  '根据Button的Enabled状态进行重画  If (nState And ODS_DISABLED) = ODS_DISABLED Then  '画外围灰框  hbr = CreateSolidBrush(RGB(132, 130, 132))  SelectObject hdc, hbr  FrameRect hdc, rct, hbr  DeleteObject hbr  '画内侧3D效果->亮色  hpen = CreatePen(PS_SOLID, 1, RGB(255, 255, 255))  SelectObject hdc, hpen  MoveToEx hdc, rct.Left + 1, rct.Top + 1, P  LineTo hdc, rct.Right - 1, rct.Top + 1  MoveToEx hdc, rct.Left + 1, rct.Top + 1, P  LineTo hdc, rct.Left + 1, rct.Bottom - 1  DeleteObject hpen  '画内侧3D效果->暗色  hpen = CreatePen(PS_SOLID, 1, RGB(189, 190, 189))  SelectObject hdc, hpen  MoveToEx hdc, rct.Left + 1, rct.Bottom - 2, P  LineTo hdc, rct.Right - 1, rct.Bottom - 2  MoveToEx hdc, rct.Right - 2, rct.Top + 1, P  LineTo hdc, rct.Right - 2, rct.Bottom - 1  DeleteObject hpen  '画阴影文字  rct.Left = rct.Left + 1  rct.Right = rct.Right + 1  rct.Bottom = rct.Bottom + 1  rct.Top = rct.Top + 1  SetTextColor hdc, GetSysColor(COLOR_BTNHIGHLIGHT)  DrawText hdc, s, LenB(StrConv(s, vbFromUnicode)), rct, DT_CENTER Or DT_SINGLELINE Or DT_VCENTER  rct.Left = rct.Left - 1  rct.Right = rct.Right - 1  rct.Bottom = rct.Bottom - 1  rct.Top = rct.Top - 1  SetTextColor hdc, GetSysColor(COLOR_GRAYTEXT)  DrawText hdc, s, LenB(StrConv(s, vbFromUnicode)), rct, DT_CENTER Or DT_SINGLELINE Or DT_VCENTER  Exit Sub  End If  '按下Button时重画  If (nState And ODS_SELECTED) = ODS_SELECTED Then  '画内部区域颜色  hbr = CreateSolidBrush(RGB(156, 186, 222))  SelectObject hdc, hbr  FillRect hdc, rct, hbr  DeleteObject hbr  '画外围灰框  hbr = CreateSolidBrush(RGB(99, 125, 165))  SelectObject hdc, hbr  FrameRect hdc, rct, hbr  DeleteObject hbr  '画内侧3D效果->亮色  hpen = CreatePen(PS_SOLID, 1, RGB(123, 158, 206))  SelectObject hdc, hpen  MoveToEx hdc, rct.Left + 1, rct.Top + 1, P  LineTo hdc, rct.Right - 1, rct.Top + 1  MoveToEx hdc, rct.Left + 1, rct.Top + 1, P  LineTo hdc, rct.Left + 1, rct.Bottom - 1  DeleteObject hpen  '画内侧3D效果->暗色  hpen = CreatePen(PS_SOLID, 1, RGB(181, 203, 231))  SelectObject hdc, hpen  MoveToEx hdc, rct.Left + 1, rct.Bottom - 2, P  LineTo hdc, rct.Right - 1, rct.Bottom - 2  MoveToEx hdc, rct.Right - 2, rct.Top + 1, P  LineTo hdc, rct.Right - 2, rct.Bottom - 1  DeleteObject hpen    rct.Left = rct.Left + 1  rct.Right = rct.Right + 1  rct.Bottom = rct.Bottom + 1  rct.Top = rct.Top + 1  SetTextColor hdc, GetSysColor(COLOR_BTNTEXT)  DrawText hdc, s, LenB(StrConv(s, vbFromUnicode)), rct, DT_CENTER Or DT_SINGLELINE Or DT_VCENTER  Exit Sub  End If  'Button得到焦点时重画  If (nState And ODS_FOCUS) = ODS_FOCUS Then  '画内部区域颜色  hbr = CreateSolidBrush(RGB(173, 203, 239))  SelectObject hdc, hbr  FillRect hdc, rct, hbr  DeleteObject hbr  '画外围灰框  hbr = CreateSolidBrush(RGB(107, 138, 181))  SelectObject hdc, hbr  FrameRect hdc, rct, hbr  DeleteObject hbr  '画内侧3D效果->亮色  hpen = CreatePen(PS_SOLID, 1, RGB(198, 223, 247))  SelectObject hdc, hpen  MoveToEx hdc, rct.Left + 1, rct.Top + 1, P  LineTo hdc, rct.Right - 1, rct.Top + 1  MoveToEx hdc, rct.Left + 1, rct.Top + 1, P  LineTo hdc, rct.Left + 1, rct.Bottom - 1  DeleteObject hpen  '画内侧3D效果->暗色  hpen = CreatePen(PS_SOLID, 1, RGB(132, 174, 222))  SelectObject hdc, hpen  MoveToEx hdc, rct.Left + 1, rct.Bottom - 2, P  LineTo hdc, rct.Right - 1, rct.Bottom - 2  MoveToEx hdc, rct.Right - 2, rct.Top + 1, P  LineTo hdc, rct.Right - 2, rct.Bottom - 1  DeleteObject hpen    SetTextColor hdc, GetSysColor(COLOR_BTNTEXT)  DrawText hdc, s, LenB(StrConv(s, vbFromUnicode)), rct, DT_CENTER Or DT_SINGLELINE Or DT_VCENTER  Else  '画外围灰框  hbr = CreateSolidBrush(RGB(132, 130, 132))  SelectObject hdc, hbr  FrameRect hdc, rct, hbr  DeleteObject hbr  '画内侧3D效果->亮色  hpen = CreatePen(PS_SOLID, 1, RGB(255, 255, 255))  SelectObject hdc, hpen  MoveToEx hdc, rct.Left + 1, rct.Top + 1, P  LineTo hdc, rct.Right - 1, rct.Top + 1  MoveToEx hdc, rct.Left + 1, rct.Top + 1, P  LineTo hdc, rct.Left + 1, rct.Bottom - 1  DeleteObject hpen  '画内侧3D效果->暗色  hpen = CreatePen(PS_SOLID, 1, RGB(189, 190, 189))  SelectObject hdc, hpen  MoveToEx hdc, rct.Left + 1, rct.Bottom - 2, P  LineTo hdc, rct.Right - 1, rct.Bottom - 2  MoveToEx hdc, rct.Right - 2, rct.Top + 1, P  LineTo hdc, rct.Right - 2, rct.Bottom - 1  DeleteObject hpen  '画文字  SetTextColor hdc, GetSysColor(COLOR_BTNTEXT)  DrawText hdc, s, LenB(StrConv(s, vbFromUnicode)), rct, DT_CENTER Or DT_SINGLELINE Or DT_VCENTER  End IfEnd Sub'新的窗口消息处理过程，将被插入到默认处理过程之前Private Function SubWndProc(ByVal hWnd As Long, ByVal Msg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long Dim di As DRAWITEMSTRUCT  If Msg = WM_DESTROY Then Terminate (hWnd)  '处理自画消息  If Msg = WM_DRAWITEM Then  CopyMemory di, ByVal lParam, Len(di)  '判断是自画Button  If di.CtlType = ODT_BUTTON Then  DrawButton di.hwndItem, di.hdc, di.rcItem, di.itemState  '不返回VB的默认Button绘制过程  SubWndProc = 1  Exit Function  End If  End If  '调用默认的窗口处理过程  SubWndProc = CallWindowProc(PrevWndProc, hWnd, Msg, wParam, lParam)End Function'子类化入口Public Sub Init(hWnd As Long) PrevWndProc = SetWindowLong(hWnd, GWL_WNDPROC, AddressOf SubWndProc)End Sub'子类化出口Public Sub Terminate(hWnd As Long) Call SetWindowLong(hWnd, GWL_WNDPROC, PrevWndProc)End Sub' -- 模块结束 -- '

3. Visual Basic .NET子类化的实现 

　　.NET中使用子类化技术要比VB6中简单，因为微软在.NET中已经提供了接口，不需要我们再自己SetWindowLong了，我们做的是Overrides（覆盖） WndProc过程即可。 
　　Overrides Protected Sub WndProc( ByRef m As Message )参数m实现了Windows的消息类型。 

　　下面的例子将演示如何将About加入窗口的系统菜单。 

①创建工程 

　　创建一个VB.NET的Windows Application工程。 

②录入代码

代码Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->Public Class Form1 Inherits System.Windows.Forms.Form '中间隐去了.NET自动生成的代码 ' – 引用Win32Api Private Declare Function GetSystemMenu Lib "user32" (ByVal hWnd As IntPtr, ByVal bRevert As Int32) As Int32 Private Declare Function InsertMenu Lib "user32" Alias "InsertMenuA" (ByVal hMenu As Int32, ByVal nPosition As Int32, ByVal wFlags As Int32, ByVal wIDNewItem As Int32, ByVal lpNewItem As String) As Int32 Private Const MF_BYCOMMAND = &H0& Private Const MF_BYPOSITION = &H400& Private Const MF_STRING = &H0& Private Const MF_SEPARATOR = &H800& Private Const WM_SYSCOMMAND = &H112 Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load InsertMenu(GetSystemMenu(Me.Handle, False), 0, MF_BYPOSITION Or MF_SEPARATOR, 2001, "") '加入一条分割线 'GetSystemMenu(Me.Handle, False)是得到系统菜单的句柄，第二个参数为True的话不能改变系统菜单，所以要设为False InsertMenu(GetSystemMenu(Me.Handle, False), 0, MF_BYPOSITION Or MF_STRING, 2002, "About Me(&A)") '加入About me菜单在系统菜单中 End Sub Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message) '类化窗口--覆盖WndProc过程 If m.Msg = WM_SYSCOMMAND Then If m.WParam.ToInt32 = 2002 Then MsgBox("About Context", vbInformation, "About...") End If End If '调用窗口默认的处理过程 MyBase.WndProc(m) End Sub End Class

4. 小结 

　　子类化技术可以让我们实现一些使用VB在正常条件下无法完成的任务，而且通过这些技术可以更为深入的学习Windows编程，成为VB开发人员中的高手。

转载：http://www.cnblogs.com/huanghai/archive/2010/04/30/1724904.html