或 例如: ----------------------------------------------------------------------------- int GetWindowText( HWND hWnd, // handle of window or control with text LPTSTR lpString, // address of buffer for text int nMaxCount // maximum number of characters to copy ); 该 API 取得WINDOW Title Bar的文字，而传回值是放入lpString的character个数。 VB的宣告如下：
Decl are Function GetWindowText Lib "user32" Alias "GetWindowTextA" _ (ByVal hwnd As Long, _ ByVal lpString As String, _ ByVal cch As Long) As Long 范例一 ***************************************************************************** Dim CharCnt As Long Dim lpString As String Dim tmpstr As String Dim NullPos As Long
----------------------------------------------------------------------------- LONG RegQueryValueEx( HKEY hKey, // handle of key to query LPTSTR lpszValueName, // address of name of value to query LPDWORD lpdwReserved, // reserved LPDWORD lpdwType, // address of buffer for value type LPBYTE lpbData, // address of data buffer LPDWORD lpcbData // address of data buffer size ); VB的宣告(由API检视员中Copy下来者) Declare Function RegQueryValueEx Lib "advapi32.dll" Alias "RegQueryValueExA" _ (ByVal hKey As Long, _ ByVal lpValueName As String, _ ByVal lpReserved As Long, _ lpType As Long, _ lpData As Any, _ lpcbData As Long) As Long ----------------------------------------------------------------------------- 仔细看一下第三个参数，WIN API中是LPDWORD可是VB中麽会是用ByVal的方式传递 呢？原因在於 lpReserved一定要传Null进去，VB在呼叫时便在 这参数的位置上填0(见 范例三)。为何传Null就得这做？我们可以这麽想，我们 在程式中下指令，告诉VB要以 ByVal 的方式传0出去，而WIN API里，它可不管VB是ByVal或ByRef，API 认定我们传 进 来的就是它需要的，所以了，第三个参数在API中认定我们传进的是一个Address，而VB 传0进去，那代表API若去取得它的内容，便会取得Address 0 的内容，或许Window的 Null值便是指向Address 0呢！另一个作法比较直接，将VB宣告的第三个参数宣告由 ByVal lpReserved As Long改成 ByVal lpReserved as String而使用时固定传 vbNullString 进去也可以。这里在一个观念，那就是VB对Win API的宣告，纯粹是给VB 自己看的，在API中定义了一个指标的参数，Api检视员会将之宣告成ByRef的方式(字串 除外)，但我们可随需要而更动它，一个原始应为ByRef的参数宣告，我们可以将之改为 ByVal的方式，只要我们能取得参数的位址，而将这型态为Long的位址以ByVal传出去， Win API 端根本不知道VB端是用什麽方式传，反正只要我们传了一Long值进去，Win API 就会以这个Long值当作是Address来运作。
----------------------------------------------------------------------------- Declare Function RegQueryLong Lib "advapi32.dll" Alias "RegQueryValueExA" _ (ByVal hKey As Long, _ ByVal lpValueName As String, _ ByVal lpReserved As Long, _ lpType As Long, _ lpData As Long, _ lpcbData As Long) As Long
Declare Function RegQueryString Lib "advapi32.dll" Alias "RegQueryValueExA" _ (ByVal hKey As Long, _ ByVal lpValueName As String, _ ByVal lpReserved As Long, _ lpType As Long, _ Byval lpData As String, _ lpcbData As Long) As Long ----------------------------------------------------------------------------- 使用两个宣告来解决这个问题，依不同的lpType呼叫不同的函式，即lpType= REG_ DWORD时，呼叫RegQueryLong, lpType = REG_SZ时则为RegQueryString这也可以让我们 了解为何VB API的宣告为什麽要有Alias的存在。
范例三 ***************************************************************************** Declare Function RegCloseKey Lib "advapi32.dll" (ByVal hKey As Long) _ As Long Declare Function RegOpenKeyEx Lib "advapi32.dll" Alias "RegOpenKeyExA" (ByVal hKey As Long, ByVal lpSubKey As String, ByVal ulOptions As Long, _ ByVal samDesired As Long, phkResult As Long) As Long Declare Function RegQueryString Lib "advapi32.dll" Alias _ "RegQueryValueExA" (ByVal hKey As Long, _ ByVal lpValueName As String, ByVal lpReserved As Long, _ lpType As Long, ByVal lpData As String, lpcbData As Long) As Long Const REG_EXPAND_SZ = 2 Const HKEY_CLASSES_ROOT = &H80000000 Const READ_CONTROL = &H20000 Const STANDARD_RIGHTS_READ = (READ_CONTROL) Const KEY_QUERY_VALUE = &H1 Const KEY_ENUMERATE_SUB_KEYS = &H8 Const KEY_NOTIFY = &H10 Const SYNCHRONIZE = &H100000 Const KEY_READ = ((STANDARD_RIGHTS_READ Or _ KEY_QUERY_VALUE Or KEY_ENUMERATE_SUB_KEYS Or _ KEY_NOTIFY) And (Not SYNCHRONIZE))
Dim key5 As String, ValueName as String, strBuff&nb
注：本站部分文章源于互联网，版权归原作者所有！如有侵权，请原作者与本站联系，本站将立即删除！ 本站文章除特别注明外均可转载，但需注明出处！ [MinTao学以致用网] 
