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VB 子类化技术详解

减小字体 增大字体 作者:佚名  来源:本站整理  发布时间:2010-09-27 09:53:10

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

VBScript code复制代码
 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 Sub

④加入一个模块并录入代码
 

VBScript code复制代码
Option Explicit
' -- 引用Win32Api –
'得到默认的窗口消息处理过程的地址需要的API
Private 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API
Private 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API
Private 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 = &H2
Private Const WM_DRAWITEM = &H2B
Private Type RECT
    Left As Long
    Top As Long
    Right As Long
    Bottom As Long
End Type
'WM_DRAWITEM需要处理的结构体
Private Type DRAWITEMSTRUCT
    CtlType As Long
    CtlID As Long
    itemID As Long
    itemAction As Long
    itemState As Long
    hwndItem As Long
    hdc As Long
    rcItem As RECT
    itemData As Long
End Type
' Owner draw 常量
Private Const ODT_BUTTON = 4
' Owner draw 动作
Private Const ODA_DRAWENTIRE = &H1
Private Const ODA_SELECT = &H2
Private Const ODA_FOCUS = &H4
' Owner draw 状态
Private Const ODS_SELECTED = &H1
Private Const ODS_GRAYED = &H2
Private Const ODS_DISABLED = &H4
Private Const ODS_CHECKED = &H8
Private 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 Long
Private Declare Function CreateSolidBrush Lib "gdi32" (ByVal crColor As Long) As Long
Private Declare Function DeleteObject Lib "gdi32" (ByVal hObject As Long) As Long
Private Declare Function GetSysColor Lib "user32" (ByVal nIndex As Long) As Long
'色彩常量
Const COLOR_SCROLLBAR = 0
Const COLOR_BACKGROUND = 1
Const COLOR_ACTIVECAPTION = 2
Const COLOR_INACTIVECAPTION = 3
Const COLOR_MENU = 4
Const COLOR_WINDOW = 5
Const COLOR_WINDOWFRAME = 6
Const COLOR_MENUTEXT = 7
Const COLOR_WINDOWTEXT = 8
Const COLOR_CAPTIONTEXT = 9
Const COLOR_ACTIVEBORDER = 10
Const COLOR_INACTIVEBORDER = 11
Const COLOR_APPWORKSPACE = 12
Const COLOR_HIGHLIGHT = 13
Const COLOR_HIGHLIGHTTEXT = 14
Const COLOR_BTNFACE = 15
Const COLOR_BTNSHADOW = 16
Const COLOR_GRAYTEXT = 17
Const COLOR_BTNTEXT = 18
Const COLOR_INACTIVECAPTIONTEXT = 19
Const COLOR_BTNHIGHLIGHT = 20
Private Declare Function FillRect Lib "user32" (ByVal hdc As Long, lpRect As RECT, ByVal hBrush As Long) As Long
Private Declare Function FrameRect Lib "user32" (ByVal hdc As Long, lpRect As RECT, ByVal hBrush As Long) As Long
Private 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 = 0
Const PS_DASH = 1 ' -------
Const PS_DOT = 2 ' .......
Const PS_DASHDOT = 3 ' _._._._
Const PS_DASHDOTDOT = 4 ' _.._.._
Const PS_NULL = 5
Const PS_INSIDEFRAME = 6
Const PS_USERSTYLE = 7
Const PS_ALTERNATE = 8
Const PS_STYLE_MASK = &HF
Private Declare Function MoveToEx Lib "gdi32" (ByVal hdc As Long, ByVal x As Long, ByVal y As Long, lpPoint As POINTAPI) As Long
Private Declare Function LineTo Lib "gdi32" (ByVal hdc As Long, ByVal x As Long, ByVal y As Long) As Long
Private Type POINTAPI
    x As Long
    y As Long
End Type
Private 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 Long
Private Const DT_SINGLELINE = &H20
Private Const DT_CENTER = &H1
Private Const DT_VCENTER = &H4
Private Declare Function SetTextColor Lib "gdi32" (ByVal hdc As Long, ByVal crColor As Long) As Long
Private Declare Function SetBkMode Lib "gdi32" (ByVal hdc As Long, ByVal nBkMode As Long) As Long
Private 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 If
End 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 -- '
 

⑤运行结果

现在我们比较一下传统式样Button和新新式样Button的区别吧,这个例子虽然代码很多,而且用到了一些GDI函数,但是子类化技术实际上只需要Init、Terminate、SubWndProc三个函数,因为我们处理了较复杂的重画操作,所以样例看上去很长。

需要指出的是不正确的子类化是非常危险的,将导致一个General Protection Fault(GPF)错误,致使VB应用立即崩溃。
  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

启动Visual Basic 6同时创建一个标准EXE工程。

②在窗体中录入代码

VBScript code复制代码
Private Declare Function GetSystemMenu Lib "user32" (ByVal hWnd As Long, ByVal bRevert As Long) As Long
Private Declare Function InsertMenu Lib "user32" Alias "InsertMenuA" (ByVal hMenu As Long, ByVal nPosition As Long, ByVal wFlags As Long, ByVal wIDNewItem As Long, ByVal lpNewItem As String) As Long

Private Const MF_BYCOMMAND = &H0&
Private Const MF_BYPOSITION = &H400&
Private Const MF_STRING = &H0&
Private Const MF_SEPARATOR = &H800&

Private Sub Form_Load()

    InsertMenu GetSystemMenu(Me.hWnd, False), 0, MF_BYPOSITION Or MF_SEPARATOR, 2001, ""
    InsertMenu GetSystemMenu(Me.hWnd, False), 0, MF_BYPOSITION Or MF_STRING, 2002, "About Me(&A)"

    '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 Sub

③加入一个模块并录入代码

VBScript code复制代码
Option Explicit

Private Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hWnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Private 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

Const GWL_WNDPROC = (-4&)
Const WM_DESTROY = &H2

Dim PrevWndProc&

Private Const WM_SYSCOMMAND = &H112

Public Sub Init(hWnd As Long)

    '子类化入口
    PrevWndProc = SetWindowLong(hWnd, GWL_WNDPROC, AddressOf SubWndProc)

End Sub

Public Sub Terminate(hWnd As Long)

    '子类化出口
    Call SetWindowLong(hWnd, GWL_WNDPROC, PrevWndProc)

End Sub

Private Function SubWndProc(ByVal hWnd As Long, ByVal Msg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long

    '新的窗口消息处理过程,将被插入到默认处理过程之前
    If Msg = WM_DESTROY Then Terminate (Form1.hWnd)

    If wParam = 2002 Then

        MsgBox "About Context", vbInformation, "About..."

    End If

    '调用默认的窗口处理过程
    SubWndProc = CallWindowProc(PrevWndProc, hWnd, Msg, wParam, lParam)

End Function

' -- 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

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。

Tags:子类化 VB VB.Net

作者:佚名
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