在Windows API InsertMenuItem中需要帮助

Question

我想在其他过程中插入一个新菜单。 但是我得到一个错误：

尝试读取或写入受保护的内存。 这通常表明其他内存已损坏。

按钮代码：

    Mmenuhandle = GetMenu(mainhandle) 
    Mmenucount = GetMenuItemCount(Mmenuhandle)
    Smenuhandle = GetSubMenu(Mmenuhandle, 0)
    Smenucount = GetMenuItemCount(Smenuhandle)  
    With mii  
        .cbSize = Len(mii)  
        .fMask = MIIM_STATE Or MIIM_ID Or MIIM_STRING Or MIIM_FTYPE  
        .fType = MFT_STRING  
        .fState = MFS_ENABLED  
        .wID = MENUID  
        .dwTypeData = "My Menu"  
        .cch = Len(.dwTypeData)  
    End With  
    InsertMenuItem(Smenuhandle, Smenucount + 1, True, mii) ' ERROR here  
    DrawMenuBar(mainhandle)  

声明InsertMenuItem ：

Private Declare Function InsertMenuItem Lib "user32" Alias "InsertMenuItemA" _
    (ByVal hMenu As Integer, ByVal uItem As Integer, ByVal fByPosition As Boolean, ByVal lpmii As MENUITEMINFO) As Integer

声明MENUITEMINFO ：

Public Structure MENUITEMINFO
    Public cbSize As Integer
    Public fMask As Integer
    Public fType As Integer
    Public fState As Integer
    Public wID As Integer
    Public hSubMenu As Integer
    Public hbmpChecked As Integer
    Public hbmpUnchecked As Integer
    Public dwItemData As Integer
    Public dwTypeData As String
    Public cch As Integer
    Public a As Integer  
End Structure

如何解决此错误？

Answer 1

P / Invoke代码不正确 。它似乎是从VB 6源复制的，等效名称的数据类型在VB 6中的含义与在VB.NET中的含义非常不同。

此外，句柄/指针使用固定的整数类型声明，在64位环境中将无法正常使用。 这些类型的值应始终使用专门为此目的设计的IntPtr类型声明。

并且，结构的指针需要在VB.NET中传递ByRef 。 您不能通过他们ByVal 。

您需要使用System.Runtime.InteropServices命名空间和.NET编组器中的工具来帮助您。

这是另一个原因，您永远不要只复制并粘贴在网上找到的代码而不了解它的含义和作用。

声明应如下所示：

Imports System.Runtime.InteropServices

Public NotInheritable Class NativeMethods

   Public Const MIIM_STATE As Integer = &H1
   Public Const MIIM_ID As Integer = &H2
   Public Const MIIM_STRING As Integer = &H40
   Public Const MIIM_BITMAP As Integer = &H80
   Public Const MIIM_FTYPE As Integer = &H100

   Public Const MFT_STRING As Integer = &H0

   Public Const MFS_ENABLED As Integer = &H0

   <StructLayout(LayoutKind.Sequential, CharSet:=CharSet.Auto)> _
   Public Structure MENUITEMINFO
      Public cbSize As Integer
      Public fMask As Integer
      Public fType As Integer
      Public fState As Integer
      Public wID As Integer
      Public hSubMenu As IntPtr
      Public hbmpChecked As IntPtr
      Public hbmpUnchecked As IntPtr
      Public dwItemData As IntPtr
      <MarshalAs(UnmanagedType.LPTStr)> Public dwTypeData As String
      Public cch As Integer
      Public hbmpItem As IntPtr
   End Structure

   <DllImport("user32.dll", CharSet:=CharSet.Auto, SetLastError:=False)> _
   Public Shared Function GetMenu(ByVal hWnd As IntPtr) As IntPtr
   End Function

   <DllImport("user32.dll", CharSet:=CharSet.Auto, SetLastError:=True)> _
   Public Shared Function GetMenuItemCount(ByVal hMenu As IntPtr) As Integer
   End Function

   <DllImport("user32.dll", CharSet:=CharSet.Auto, SetLastError:=False)> _
   Public Shared Function GetSubMenu(ByVal hMenu As IntPtr, ByVal nPos As Integer) As IntPtr
   End Function

   <DllImport("user32.dll", CharSet:=CharSet.Auto, SetLastError:=True)> _
   Public Shared Function InsertMenuItem(ByVal hMenu As IntPtr,
                                         ByVal uItem As Integer,
                                         <MarshalAs(UnmanagedType.Bool)> fByPosition As Boolean,
                                         ByRef lpmii As MENUITEMINFO) _
                                    As <MarshalAs(UnmanagedType.Bool)> Boolean
   End Function

   <DllImport("user32.dll", CharSet:=CharSet.Auto, SetLastError:=True)> _
   Public Shared Function DrawMenuBar(ByVal hWnd As IntPtr) As <MarshalAs(UnmanagedType.Bool)> Boolean
   End Function

End Class

然后，您可以使用如下功能（重新编写代码以使其匹配）：

  ' Get a handle to the menu assigned to a window (in this case, your form)
  Dim hMenu As IntPtr = NativeMethods.GetMenu(Me.Handle)

  ' Get a count of the total items in that menu
  Dim menuItemCount As Integer = NativeMethods.GetMenuItemCount(hMenu)

  ' Get a handle to the sub-menu at index 0
  Dim hSubMenu As IntPtr = NativeMethods.GetSubMenu(hMenu, 0)

  ' Get a count of the total items in that sub-menu
  Dim subMenuItemCount As Integer = NativeMethods.GetMenuItemCount(hSubMenu)

  ' Create and fill in a MENUITEMINFO structure, describing the menu item to add
  Dim mii As New NativeMethods.MENUITEMINFO
  With mii
     .cbSize = Marshal.SizeOf(mii)   ' prefer Marshal.SizeOf over the VB 6 Len() function
     .fMask = NativeMethods.MIIM_FTYPE Or NativeMethods.MIIM_STATE Or NativeMethods.MIIM_ID Or NativeMethods.MIIM_STRING
     .fType = NativeMethods.MFT_STRING
     .fState = NativeMethods.MFS_ENABLED
     .wID = 0                        ' your custom menu item ID here
     .hSubMenu = IntPtr.Zero
     .hbmpChecked = IntPtr.Zero
     .hbmpUnchecked = IntPtr.Zero
     .dwItemData = IntPtr.Zero
     .dwTypeData = "My Menu Item"    ' the name of your custom menu item
  End With

  ' Insert the menu item described by the above structure
  ' (notice that we're passing the structure by reference in the P/Invoke definition!)
  NativeMethods.InsertMenuItem(hSubMenu, subMenuItemCount + 1, True, mii)

  ' Force an update of the window's menu bar (again, in this case, your form)
  NativeMethods.DrawMenuBar(Me.Handle)

一切都按预期工作，至少在同一过程中。 请注意，P / Invoke是一个相当困难的主题，您不仅需要对VB.NET也需要对Win32 API有一个相当透彻的理解，才能使其正常工作。 在线复制和粘贴代码是一种固有的风险主张。 在大多数情况下，它是行不通的。 其余时间，这可能会带来安全风险。 不幸的是，您不仅需要有关Stack Overflow的答案，还可以向您解释它们的工作原理。

编辑：实际上，以上代码在各个进程之间也可以正常工作。 无需特别的努力。 我尝试在运行的记事本实例中浏览菜单，然后一切正常。 这并不是说我建议没有一个很好的理由这样做...