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If I have the hWnd of a textbox how do I get it's text?

Posted on 2004-04-19
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Last Modified: 2006-11-17
I use API, But I don't know how to get the text from a text box using API. Can someone help me? I can get the hWnd or ID of the textbox or any window or control, but what is the function to extract the text from a textbox? Thanks for your help.
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Question by:rcherne1
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by:BrianGEFF719
Comment Utility
       
Public Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long

Public Const WM_GETTEXT = &HD



code:
        dim buffer as string

        Buffer = String(255, Chr(0))
        SendMessage hwnd, WM_GETTEXT, 255, Buffer
        Buffer = Left(Buffer, InStr(1, Buffer, Chr(0)) - 1)
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Author Comment

by:rcherne1
Comment Utility
BrianGEFF719,

         I make a new projet and put two textboxes on a form, Then I drop this code in. The only thing I get is a crash of the app. What am I doing wrong?



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
Const WM_GETTEXT = &HD

Private Sub Form_Load()
    Dim Txt1_hWnd As Long
    Txt1_hWnd = Text1.hwnd
    Text1.Text = "This is a text"

    'Your Code
              Dim buffer As String
              buffer = String(255, Chr(0))
              Call SendMessage(Txt1_hWnd, WM_GETTEXT, 255, buffer)
              buffer = Left(buffer, InStr(1, buffer, Chr(0)) - 1)
    'End Your Code

    Text2.Text = buffer
End Sub
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by:BrianGEFF719
Comment Utility
I dont think you can do it from your own program, try a different text box that is not owned by your application.


-Brian
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Author Comment

by:rcherne1
Comment Utility
Actually, that’s exactly what I’m trying to do. I used the code only to simplify the problem. Can you write an example that will work? I’m changing the points to 500 because I feel this is more challenging than I first though.
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Accepted Solution

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unknown_routine earned 500 total points
Comment Utility
Hi

Use this :


Option Explicit

Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Integer, ByVal lParam As Any) As Long
Private Const WM_GETTEXT = &HD
Private Const WM_GETTEXTLENGTH = &HE


Private Sub Command1_Click()
    Dim n As Integer
 s As String
 q As Integer
s$ = Space$(255)
Dim k1, k2 As Long
n = SendMessage(Text1.hwnd, WM_GETTEXTLENGTH, k1, k2)
q = SendMessage(Text1.hwnd, WM_GETTEXT, 254, s$)
 s = Left(s, n)
 MsgBox s
End Sub

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Expert Comment

by:unknown_routine
Comment Utility
I forgot to put dims for 2 lines: add dims !


Dim s As String
Dim  q As Integer
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Expert Comment

by:GentooJava
Comment Utility
OMG!!!

It took me a couple of hours to find out why this example code crashes!
Change the following line:
     q = SendMessage(Text1.hwnd, WM_GETTEXT, 254, s$)
to
     q = SendMessage(Text1.hwnd, WM_GETTEXT, 254, ByVal s$)

If you do not pass it "ByVal", your app will crash when you make this call.  

:-)
--Nathan
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