处理单击系统菜单中的自定义按钮

Question

我已经创建了一个类，允许我添加一个"关于…"按钮添加到任何窗体的系统菜单中。此部分工作正常，该按钮由窗体的load事件添加，但我如何处理该按钮的单击？谢谢

以下是我如何添加按钮-

Private Sub mainForm_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    {More code....}
    Dim SysMenu = New SystemMenu(Me)
    {More code....}
End Sub

这是SystemMenu类-

Imports System.Windows.Forms
Public Class SystemMenu
    Private Declare Function GetSystemMenu Lib "user32" (ByVal hWnd As IntPtr, ByVal bRevert As Boolean) As IntPtr
    Private Declare Function AppendMenu Lib "user32" Alias "AppendMenuA" (ByVal hMenu As IntPtr, ByVal uFlags As Int32, ByVal uIDNewItem As IntPtr, ByVal lpNewItem As String) As Boolean
    Private Const MF_STRING As Integer = &H0
    Private Const MF_SEPARATOR As Integer = &H800
    Private m_hSysMenu As IntPtr
    Private Property hSysMenu() As IntPtr
        Get
            Return Me.m_hSysMenu
        End Get
        Set(ByVal Value As IntPtr)
            Me.m_hSysMenu = Value
        End Set
    End Property
    '**
    ' Constructor
    '*
    Protected Friend Sub New(ByRef Form As Form)
        Me.hSysMenu = GetSystemMenu(Form.Handle, False)
        AddAbout(Form)
    End Sub
    '**
    ' Add an 'About' button to the system menu of the given form
    '*
    Private Sub AddAbout(ByRef Form As Form)
        AppendMenu(Me.hSysMenu, MF_SEPARATOR, 1000, Nothing)
        AppendMenu(Me.hSysMenu, MF_STRING, 1001, "About...")
    End Sub
End Class

Answer 1

看看这个。将SubclassedSystemMenu.vb文件添加到项目中，并将其添加到主表单中

Private WithEvents sysMenu As SubclassedSystemMenu
Protected Overrides Sub OnLoad(e As System.EventArgs)
  sysMenu = New SubclassedSystemMenu(Me.Handle.ToInt32, "&About...")
End Sub

然后订阅其LaunchDialog事件并打开表单

Private Sub sysMenu_LaunchDialog() Handles sysMenu.LaunchDialog
  Dim f as New frmAbout
  f.ShowDialog(Me)
End Sub

这是SubclassedSystemMenu级

Public Class SubclassedSystemMenu
Inherits System.Windows.Forms.NativeWindow
Implements IDisposable
Private Declare Function GetSystemMenu Lib "user32" (ByVal hwnd As Int32, _
                                                     ByVal bRevert As Boolean) As Int32
Private Declare Function AppendMenu Lib "user32" Alias "AppendMenuA" (ByVal hMenu As Int32, _
                                                                      ByVal wFlags As Int32, _
                                                                      ByVal wIDNewItem As Int32, _
                                                                      ByVal lpNewItem As String) As Int32
Private Const MF_STRING As Int32 = &H0       ' Menu string format
Private Const MF_SEPARATOR As Int32 = &H800  ' Menu separator
Private Const WM_SYSCOMMAND As Int32 = &H112 ' System menu 
Private Const ID_ABOUT As Int32 = 1000       ' Our ID for the new menu item
Private mintSystemMenu As Int32 = 0                 ' Parent system menu handle
Private mintHandle As Int32 = 0                     ' Local parent window handle
Private mstrMenuItemText As String = String.Empty   ' New menu item text
Public Event LaunchDialog()
Public Sub New(ByVal intWindowHandle As Int32, _
               ByVal strMenuItemText As String)
    Me.AssignHandle(New IntPtr(intWindowHandle))
    mintHandle = intWindowHandle
    mstrMenuItemText = strMenuItemText
    ' Retrieve the system menu handle
    mintSystemMenu = GetSystemMenu(mintHandle, 0)
    If AddNewSystemMenuItem() = False Then
        Throw New Exception("Unable to add new system menu items")
    End If
End Sub
Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
    Select Case m.Msg
        Case WM_SYSCOMMAND
            MyBase.WndProc(m)
            If m.WParam.ToInt32 = ID_ABOUT Then
                If mintSystemMenu <> 0 Then
                    RaiseEvent LaunchDialog()
                End If
            End If
        Case Else
            MyBase.WndProc(m)
    End Select
End Sub
Public Sub Dispose() Implements System.IDisposable.Dispose
    If Not Me.Handle.Equals(IntPtr.Zero) Then
        Me.ReleaseHandle()
    End If
End Sub
Private Function AddNewSystemMenuItem() As Boolean
    Try
        ' Append the extra system menu items
        Return AppendToSystemMenu(mintSystemMenu, mstrMenuItemText)
    Catch ex As Exception
        Return False
    End Try
End Function
Private Function AppendToSystemMenu(ByVal intHandle As Int32, _
                                    ByVal strText As String) As Boolean
    Try
        ' Add the seperator menu item
        Dim intRet As Int32 = AppendMenu(intHandle, MF_SEPARATOR, 0, String.Empty)
        ' Add the About... menu item
        intRet = AppendMenu(intHandle, MF_STRING, ID_ABOUT, strText)
        If intRet = 1 Then
            Return True
        Else
            Return False
        End If
    Catch ex As Exception
        Return False
    End Try
End Function

最终类