by Robert N. (2 Submissions)
Category: Windows API Call/Explanation
Compatability: Visual Basic 5.0
Difficulty: Beginner
Date Added: Wed 3rd February 2021
Rating: 
(4 Votes)
The SendInput function synthesizes keystrokes, mouse motions, and button clicks.
Windows NT 4.0 SP3 or later; Windows 98
Inputs
· nInputs
[in] Specifies the number of structures in the pInputs array.
· pInputs
[in] Pointer to an array of INPUT structures. Each structure represents an event to be inserted into the keyboard or mouse input stream.
· cbSize
[in] Specifies the size, in bytes, of an INPUT structure. If cbSize is not the size of an INPUT structure, the function will fail.
Code Returns
The function returns the number of events that it successfully inserted into the keyboard or mouse input stream. If the function returns zero, the input was already blocked by another thread.
API DeclarationsDeclare Function SendInput Lib "user32.dll" (ByVal nInputs As Long, pInputs As GENERALINPUT, ByVal cbSize As Long) As Long
VBcodersConst VK_H = 72
Const VK_E = 69
Const VK_L = 76
Const VK_O = 79
Const KEYEVENTF_KEYUP = &H2
Const INPUT_MOUSE = 0
Const INPUT_KEYBOARD = 1
Const INPUT_HARDWARE = 2
Private Type MOUSEINPUT
dx As Long
dy As Long
mouseData As Long
dwFlags As Long
time As Long
dwExtraInfo As Long
End Type
Private Type KEYBDINPUT
wVk As Integer
wScan As Integer
dwFlags As Long
time As Long
dwExtraInfo As Long
End Type
Private Type HARDWAREINPUT
uMsg As Long
wParamL As Integer
wParamH As Integer
End Type
Private Type GENERALINPUT
dwType As Long
xi(0 To 23) As Byte
End Type
Private Declare Function SendInput Lib "user32.dll" (ByVal nInputs As Long, pInputs As GENERALINPUT, ByVal cbSize As Long) As Long
Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (pDst As Any, pSrc As Any, ByVal ByteLen As Long)
Private Sub Form_KeyPress(KeyAscii As Integer)
'Print the key on the form
Me.Print Chr$(KeyAscii);
End Sub
Private Sub Form_Paint()
'Clear the form
Me.Cls
'call the SendKey-function
SendKey VK_H
SendKey VK_E
SendKey VK_L
SendKey VK_L
SendKey VK_O
End Sub
Private Sub SendKey(bKey As Byte)
Dim GInput(0 To 1) As GENERALINPUT
Dim KInput As KEYBDINPUT
KInput.wVk = bKey 'the key we're going to press
KInput.dwFlags = 0 'press the key
'copy the structure into the input array's buffer.
GInput(0).dwType = INPUT_KEYBOARD ' keyboard input
CopyMemory GInput(0).xi(0), KInput, Len(KInput)
'do the same as above, but for releasing the key
KInput.wVk = bKey ' the key we're going to realease
KInput.dwFlags = KEYEVENTF_KEYUP ' release the key
GInput(1).dwType = INPUT_KEYBOARD ' keyboard input
CopyMemory GInput(1).xi(0), KInput, Len(KInput)
'send the input now
Call SendInput(2, GInput(0), Len(GInput(0)))
End Sub