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Question : How do I retrieve text from a website
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Hello to all,
I need to write some code in to import currency exchange rate data from a website into a database table and display it in a form.
I found the following code , and I was wondering if someone can explain how to use it:
******************************************************************************************************************************************* 'I had to write some code in VB6 to import currency exchange rate data into a database and I thought I'd post it here in case anyone else needed to do the same thing. 'The API part of the code was from Ryan Woodward who has many thanks from me! 'The Text from the website can be retrieved and placed in a text field or string by using a simple function call from within any form event, 'eg. if you had a command button called btnRetrieve you could put it in btnRetrieve_Click(). 'I then used Split, Left, Mid and Right to extract the parts of the data which I needed. 'In the following, txtURL is the web-site address and txtURLSource is the string variable you are placing it into. ' 'txtURLSource = OpenUrl(txtURL) ' 'To implement it, create a module called rwInetXfer and copy the following into it. 'It worked a treat for me, both in VB6 and when I imported it into Access2K. ' '--rwInetXfer ':: ::ver 1.0vb:: ':: ::orig. author R. Woodward:: ':: ::[email protected]:: ':: '::WHY: ':: Many versions of the Microsoft Internet Transfer Control ':: that shipped with VB are buggy or unreliable ':: Here's a nice substitute with source code ':: Currently only implements OpenUrl ':: '::DESC: ':: Internet File Transfer Object ':: Retrieve internet files over http using ':: Windows system DLLs (wininet) and system network config ':: '::E.G.: ':: Dim inet As rwInetXfer ':: debug.Print "HTML SOURCE-" ':: debug.Print inet.OpenUrl("http://www.yahoo.com") '::
Option Explicit
Const ClassName = "rwInetXfer"
Public DontUseCache As Boolean
Private Enum InfoLevelEnum http_QUERY_CONTENT_TYPE = 1 http_QUERY_CONTENT_LENGTH = 5 http_QUERY_EXPIRES = 10 http_QUERY_LAST_MODIFIED = 11 http_QUERY_PRAGMA = 17 http_QUERY_VERSION = 18 http_QUERY_STATUS_CODE = 19 http_QUERY_STATUS_TEXT = 20 http_QUERY_RAW_HEADERS = 21 http_QUERY_RAW_HEADERS_CRLF = 22 http_QUERY_FORWARDED = 30 http_QUERY_SERVER = 37 http_QUERY_USER_AGENT = 39 http_QUERY_SET_COOKIE = 43 http_QUERY_REQUEST_METHOD = 45 http_STATUS_DENIED = 401 http_STATUS_PROXY_AUTH_REQ = 407 End Enum
Private Const INTERNET_OPEN_TYPE_PRECONFIG = 0 Private Const INTERNET_OPEN_TYPE_DIRECT = 1 Private Const INTERNET_OPEN_TYPE_PROXY = 3
Private Const SCUSERAGENT = "Mozilla/4.0 (compatible; MSIE 5.0; Windows NT 5.1)" Private Const INTERNET_FLAG_RELOAD = &H80000000 Private Const INTERNET_FLAG_ASYNC = &H10000000 ' this request is asynchronous (where supported)
Private Const INTERNET_FLAG_FROM_CACHE = &H1000000 ' use offline semantics Private Const INTERNET_FLAG_OFFLINE = INTERNET_FLAG_FROM_CACHE Private Const INTERNET_FLAG_EXISTING_CONNECT = &H20000000
' BOOL httpQueryInfo( ' IN HINTERNET hhttpRequest, ' IN DWORD dwInfoLevel, ' IN LPVOID lpvBuffer, ' IN LPDWORD lpdwBufferLength, ' IN OUT LPDWORD lpdwIndex, ' );
'--httpQueryInfo '::DESC: ':: Queries for information about an http request. ':: Private Declare Function httpQueryInfo Lib "wininet.dll" Alias "httpQueryInfoA" _ (ByVal hhttpRequest As Long, ByVal lInfoLevel As Long, ByRef sBuffer As Any, _ ByRef lBufferLength As Long, ByRef lIndex As Long) As Integer
Private Declare Function InternetOpen Lib "wininet.dll" Alias "InternetOpenA" _ (ByVal sAgent As String, ByVal lAccessType As Long, ByVal sProxyName As String, _ ByVal sProxyBypass As String, ByVal lFlags As Long) As Long
'--InternetOpenUrl '::DESC: ':: Open a handle for retrieving a URL '::EG: ':: hOpenUrl = InternetOpenUrl(hOpen, sUrl, vbNullString, 0, INTERNET_FLAG_RELOAD, 0) ':: hOpenUrl = InternetOpenUrl(hOpen, sUrl, vbNullString, 0, INTERNET_FLAG_FROM_CACHE, 0) ':: hOpenUrl = InternetOpenUrl(hOpen, sUrl, vbNullString, 0, INTERNET_FLAG_EXISTING_CONNECT, 0) ':: hOpenUrl = InternetOpenUrl(hOpen, sUrl, vbNullString, 0, 0, 0) ':: Private Declare Function InternetOpenUrl Lib "wininet.dll" Alias "InternetOpenUrlA" _ (ByVal hOpen As Long, ByVal sURL As String, ByVal sHeaders As String, _ ByVal lLength As Long, ByVal lFlags As Long, ByVal lContext As Long) As Long
Private Declare Function InternetReadFile Lib "wininet.dll" _ (ByVal hFile As Long, ByVal sBuffer As String, ByVal lNumBytesToRead As Long, _ lNumberOfBytesRead As Long) As Integer
Private Declare Function InternetCloseHandle Lib "wininet.dll" _ (ByVal hInet As Long) As Integer
Private Declare Function InternetGetLastResponseInfo Lib "wininet.dll" Alias "InternetGetLastResponseInfoA" _ (lpdwError As Long, ByVal lpszBuffer As String, ByVal lpdwBufferLength As Long) As Integer
'--OpenUrl(url) '::DESC: ':: Retrieve the page specified by "url" ':: Returns string of page source ':: On error, returns "error #" ':: e.g. page not found returns "error 404" ':: Public Function OpenUrl(ByVal sURL As String) As String #If DEVREL < 1 Then On Error GoTo exitfunc #End If Dim S As String Dim sReadBuf As String * 2048 'a data buffer for InternetOpen fcns Dim bytesRead As Long Dim hInet As Long 'wininet handle Dim hUrl As Long 'url request handle Dim flagMoreData As Boolean Dim ret As String ' used for callling httpQueryInfo Dim sErrBuf As String * 255 Dim sErrBufLen As Long Dim dwIndex As Long ' return codes and err code saves Dim lastErr As Long Dim bRet As Boolean Dim wRet As Integer ' http status code Dim httpCode As Integer ' grab a handle for using wininet hInet = InternetOpen(SCUSERAGENT, INTERNET_OPEN_TYPE_PRECONFIG, vbNullString, vbNullString, 0) If Err.LastDllError <> 0 Then lastErr = Err.LastDllError ret = "error (wininet.dll," & lastErr & ")" GoTo exitfunc End If ' retrieve the requested URL If DontUseCache Then hUrl = InternetOpenUrl(hInet, sURL, vbNullString, 0, INTERNET_FLAG_RELOAD, 0) Else hUrl = InternetOpenUrl(hInet, sURL, vbNullString, 0, 0, 0) End If If Err.LastDllError <> 0 Then lastErr = Err.LastDllError ret = "error (wininet.dll," & lastErr & ")" GoTo exitfunc End If ' get query info, this should give us a status code among other things sErrBufLen = 255 bRet = httpQueryInfo(hUrl, http_QUERY_STATUS_CODE, ByVal sErrBuf, sErrBufLen, dwIndex) If Err.LastDllError <> 0 Then lastErr = Err.LastDllError ret = "error (wininet.dll," & lastErr & ")" GoTo exitfunc End If ' sErrBuf should now hopefully contain http status code stuff ' if the call failed, no status info was returned (i.e. sErrBuf is empty) ' then throw error If sErrBufLen = 0 Or Not bRet Then ret = "error" GoTo exitfunc Else ' retrieve the http status code httpCode = CInt(Left(sErrBuf, sErrBufLen)) If httpCode >= 300 Then ret = "error " & httpCode GoTo exitfunc End If End If ' if we made it this far, then we can begin retrieving data flagMoreData = True Do While flagMoreData sReadBuf = vbNullString wRet = InternetReadFile(hUrl, sReadBuf, Len(sReadBuf), bytesRead) If Err.LastDllError <> 0 Then lastErr = Err.LastDllError ret = "error (wininet.dll," & lastErr & ")" GoTo exitfunc End If If wRet <> 1 Then ret = "error" GoTo exitfunc End If S = S & Left$(sReadBuf, bytesRead) If Not CBool(bytesRead) Then flagMoreData = False Loop ret = S exitfunc: If hUrl <> 0 Then InternetCloseHandle (hUrl) If hInet <> 0 Then InternetCloseHandle (hInet) OpenUrl = ret End Function
Private Sub Class_Initialize() DontUseCache = False End Sub ********************************************************************************************************************************************
I'm new to MS Access, so please elaborate your answers.
Thanks in advance!
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Answer : How do I retrieve text from a website
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I feel I must have misunderstood your request, but if so, please elaborate in your next post.
I have put a button on a form and added a click handler, then put the following line in:
Beep(440,1000);
so you get
void __fastcall TForm1::Button1Click(TObject *Sender) { Beep(440,1000); }
This generates a 440Hz tone for 1000ms (1 Second) whenever the button is clicked.
Note: This function does not work this way in Win95 (the function call can be made, but the parameters are ignored, and a default bleep is played), but should be OK with Windows NT onwards. I have run the above on XP and did indeed get the beep.
The frequency parameter can be from 37 (low) to 32767 (so high you will not hear it).
Hope this helps.
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