VB:如何发送WM_KEYDOWN和WM_KEYUP消息？

其实没什么说的，只是最近一段时间问的人比较多，所以写上几句

简单的说，有两个需要注意的地方，一是要用postmessage发送消息，二是这两个消息lparam参数比较复杂，发送消息的时候要构造好lparam参数，下面给出示例代码：

Option Explicit

Private Declare Function MapVirtualKey Lib "user32" Alias "MapVirtualKeyA" (ByVal wCode As Long, ByVal wMapType As Long) As Long

Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long

Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long

Private Declare Function FindWindowEx Lib "user32" Alias "FindWindowExA" (ByVal hWnd1 As Long, ByVal hWnd2 As Long, ByVal lpsz1 As String, ByVal lpsz2 As String) As Long

Private Const WM_KEYDOWN = &H100

Private Const WM_KEYUP = &H101

Private Declare Function PostMessage Lib "user32" Alias "PostMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long

Private Sub Command1_Click()

Dim jsb As Long

jsb = FindWindow("notepad", vbNullString)

Dim mhwnd As Long

mhwnd = FindWindowEx(jsb, 0, "edit", vbNullString)

Dim lParam As Long

lParam = makelparam(vbKey5, False)

PostMessage mhwnd, WM_KEYDOWN, vbKey5, lParam

lParam = makelparam(vbKey5, True)

PostMessage mhwnd, WM_KEYUP, vbKey5, lParam

End Sub

Private Function makelparam(ByVal VirtualKey As Long, ByVal flag As Boolean) As Long

Dim s As String

Dim Firstbyte As String 'lparam参数的24-31位

If flag = False Then 'keydown

Firstbyte = "00"

Else

Firstbyte = "C0" 'keyup

End If

Dim Scancode As Long

'获得虚拟键扫描码

Scancode = MapVirtualKey(VirtualKey, 0)

Dim Secondbyte As String 'lparam参数的16-23位，即虚拟键扫描码

Secondbyte = Right("00" & Hex(Scancode), 2)

s = Firstbyte & Secondbyte & "0001" '0001为lparam参数的0-15位，即发送次数

makelparam = Val("&H" & s)

End Function