Question

I am new to using Windows API functions in VBA and I can’t find what the keys(0) exactly does/means. It is also not in a bracket/parentheses so I do not understand how it works. Thanks in advance!

Private Declare PtrSafe Function GetKeyboardState Lib "user32" _
(pbKeyState As Byte) As Long

Property Get Value() As Boolean

    Dim keys(0 To 255) As Byte
    GetKeyboardState keys(0) '<< Can someone explain what this is doing?
    Value = keys(VK_NUMLOCK)

End Property

Answer 1

I’m assuming that you already know that GetKeyboardState is used to obtain an array of the state of your keys.

When you pass keys(0) essentially you are providing the memory location of the array to the Win API function. By doing this, your array is passed by reference to the function and the array you pass is filled with the data.

Here is sample usage copied from the linked page which I’m providing only because it has lots of comments:

' Display the key status of the Enter and Backspace keys
' Enter's virtual key code = 13; Backspace's virtual key code = 8
Dim keystat(0 To 255) As Byte ' receives key status information for all keys
Dim retval As Long ' return value of function

retval = GetKeyboardState(keystat(0)) ' In VB, the array is passed by referencing element #0.
' Display info about Enter
If (keystat(13) And &H01) = &H01 Then Debug.Print "Enter is being pressed."
If (keystat(13) And &H80) = &H80 Then Debug.Print "Enter is toggled."
' Display info about Backspace
If (keystat(8) And &H01) = &H01 Then Debug.Print "Backspace is being pressed."
If (keystat(8) And &H80) = &H80 Then Debug.Print "Backspace is toggled.