启动Visual Basic，新建标准EXE工程，在工程中添加一标准模块，名称可以是默认的。在标准模块的声明部分加入下列代码：
菜单API函数声明
Public Declare Function GetSystemMenu Lib "user32"
(ByVal hwnd As Long, ByVal bRevert As Long) As Long
Public Declare Function
AppendMenu Lib "user32" Alias "AppendMenuA" (ByVal hMenu As Long, ByVal wFlags
As Long, ByVal wIDNewItem As Long, ByVal lpNewItem As Any) As Long
菜单API函数常数声明
Public Const MF_BYCOMMAND = "H0"
Public Const
MF_SEPARATOR ="H800"
Public Const MF_STRING = "H0" 有关窗口函数的API函数声明
Public
Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hwnd
As Long, ByVal nIndex As Long,ByVal dwNewLong As Long) As Long
Public 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
Public Declare Function DefWindowProc
Lib "user32" Alias "DefWindowProcA" (ByVal hwnd As Long, ByVal wMsg As Long,
ByVal wParam As Long, ByVal lParam As Long) As Long 消息
Public Const GWL DPROC
= (-4)
Public Const WM_NCLBUTTONDOWN = "HA1"
Public Const
WM_NCRBUTTONDOWN = "HA4"
Public Const WM_USER = "H400"
Public Const
WM_SYSCOMMAND = "H112"
Public Const HTSYSMENU = 3
Public Const HTCAPTION =
2 自定义菜单项的标识号偏移量
Public Const IDM_SEPARATOR = 1
Public Const IDM_MYABOUT =
2 其他变量
Dim sHwnd As Long
Dim OldProc As Long
接着可向标准模块添加下面两个过程： Public
Sub AddMenu(frm As Form) 置换窗口函数过程
sHwnd = frm.hwnd
OldProc =
SetWindowLong(frm.hwnd, GWL_WNDPROC, AddressOf AddCallBack)
End Sub
Public
Sub Release() 释放自定义窗口函数过程
SetWindowLong sHwnd,GWL_WNDPROC, OldProc
End
Sub
最后向标准模块中添加一自定义窗口函数过程：
Public Function AddCallBack(ByVal hwnd As Long,
ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long Select
Case wMsg Case WM_SYSCOMMAND
系统消息
Select Case wParam 测试
Case WM_USER
IDM_MYABOUT
"关于..."菜单项
此处可加入用户需要自己处理"关于…" 菜单项的代码
MsgBox
"单击了添加的菜单条目",vbOKOnly
Case Else 其它菜单项交换系统处理
AddCallBack =DefWindowProc(hwnd, wMsg, wParam,
lParam)
End Select
Exit Function
Case Else
AddCallBack =
CallWindowProc(OldProc, hwnd, wMsg, wParam, lParam) End
Select
End
Function 关闭标准模块的代码窗口，打开窗体的代码窗口， 在Form_Load()过程中加入下列代码：
加载自定义窗口过程
AddMenu Me 获得系统菜单的句柄 Dim
hMenu As Long hMenu = GetSystemMenu(Me.hwnd, 0)
在系统菜单中添加自定义2条菜单项
AppendMenu hMenu, MF_SEPARATOR Or MF_BYCOMMAND,
IDM_SEPARATOR,
vbNullString 分隔符 AppendMenu hMenu, MF_BYCOMMAND Or
MF_STRING,
WM_USER IDM_MYABOUT, "关于..." "关于…"菜单项
在Form_Unload过程中加入下列代码：
Release 释放自定义窗口过程
到此，代码的输入工作完成，接下来的是进行测试。单击启动按钮或按F5，启动工程，用鼠标单击窗体左上角的图标弹出系统菜单，看看是否如愿。千万要注意的一点是，在结束工程时，一定要用窗体右上角的关闭按钮或者系统菜单中的关闭菜单项，否则的话，会造成Visual
Basic系统崩溃，出现非法操作的错误，所以在测试工程前，最好对工程进行保存。
以上程序在Windows95，Visual
Basic6.0环境下调试通过。
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