"Variable" is not declared. it may be inaccessible due to its protection level

Question

 This is my code:::::

Public Class Form1

    Private Declare Function Key Lib "user32" Alias "GetAsyncKeyState" (ByVal Key As Keys) As Keys

    Dim Count As Integer = 0

    Private Sub points()

        Dim PosX As Integer = Form1.MousePosition.X

        Dim PosY As Integer = Form1.MousePosition.Y

        Dim Point = "X: " & PosX & " Y: " & PosY

        If Count = 1 Then

            Label1.Text = Point

        ElseIf Count = 2 Then

            Label2.Text = Point

        ElseIf Count = 3 Then

            Label3.Text = Point

        ElseIf Count = 4 Then

            Label4.Text = Point

        End If

    End Sub

    Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick

        If Key(Keys.LButton) Then

            Count = Count + 1

            points()

        End If

        If Count = 4 Then

            Count = 0

        End If

    End Sub

End Class

This is my error message:

Error 1 'Label1' is not declared. It may be inaccessible due to its protection level.

Error 2 'Label2' is not declared. It may be inaccessible due to its protection level.
Error 3 'Label3' is not declared. It may be inaccessible due to its protection level.
Error 4 'Label4' is not declared. It may be inaccessible due to its protection level.

I don't know how to fix this error.

Thanks for the help.

Chasman

Answer 1

Is it an inherited Form? Do you have these labels on the Form?

If I add the 4 labels, the error message I get is that Option Strict On, which is the recommended setting, doesn't allow implicit conversions from bool to System.Windows.Forms.Keys.

The function return value must be of type Short, not Keys.

You may consider putting the labels into an array so you can access them by Labels(Count-1) instead of these If statements (that could also be replaced by Select Case).

I'd use the original name GetAsyncKeyState as it's well-known, instead of just "Key".

EDIT: I Forgot to mention: Look at http://msdn.microsoft.com/en-us/library/ms646293(VS.85).aspx to see how to correctly interpret the function return value.

---

Armin

Answer 2

Please excuse this newbie reply.  I did not put the labels on the form.  After I did that, all errors are gone.  Thanks for your help Armin.  I'm just learning VB.

Also, thanks for the array recommendation.  I need to access more than four points and it would be cumbersome to have a bunch of "If-then" statements.

How would you code for the array?

Chasman

Answer 3

Hi Chasman,

I'd write it this way:

Public Class Form1

   Private Declare Function GetAsyncKeyState Lib "user32" (ByVal Key As Keys) As Short

   Private Count As Integer
   Private ReadOnly _Labels As Label()

   Public Sub New()

      InitializeComponent()

      _Labels = New Label() {Label1, Label2, Label3, Label4}

   End Sub

   Private Sub points()

      Dim Pos = MousePosition
      Dim Point = "X: " & Pos.X & " Y: " & Pos.Y

      _Labels(Count).Text = Point

   End Sub

   Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs)

      If (GetAsyncKeyState(Keys.LButton) And &H8000S) <> 0 Then
         Count = (Count + 1) Mod _Labels.Length
         points()
      End If

   End Sub

End Class

I do not question your overall approach because I think it's mainly about getting practice.

Just ask if something's unclear about the modifications made.

---

Armin

Answer 4

Armin,

Your code above brings up the form.  I have the labels on the form, but it does not record the position of the mouse clicks.  I don't see the problem in your code.  I am using VB 2010 Express.  Thanks.

Chasman

Answer 5

Your code above brings up the form.  I have the labels on the form, but it does not record the position of the mouse clicks.  I don't see the problem in your code.  I am using VB 2010 Express.  Thanks.

Oops, I'm sorry, I've deleted something to make it compile. Just add it again:

   Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick

EDIT: Maybe you will also have to change "And &H8000S" to "And 1".

---

Armin

Answer 6

I didn't want you to work this hard.

I added "Handles Timer1.Tick" to the end of that line and changed "And &H8000S" to "And 1" but it still doesn't record the clicks.

Chasman

Answer 7

Got this message:

"Error 1 Handles clause requires a WithEvents variable defined in the containing type or one of its base types." 

Answer 8

Got this message:

"Error 1 Handles clause requires a WithEvents variable defined in the containing type or one of its base types." 

Ok. Your initial post already contained "Handles...". Therefore, and because you didn't mention this error in that post, I assumed you already have a timer on the Form. If not, you must add it. Just add it from the toolbox to the Form as you did with the labels.

---

Armin

Answer 9

Thanks Armin.  You've been very helpful.

Chasman