177.htm

一些简单的编程例子 都是网页的形式

<p>判断一个文件是否在IE的缓存中 </p>
<p></p>
<p>当你建立一个联到网上文件的快捷方式时，你可能需要知道它是否已经被访问过，于是你就可以适当地改变链接的颜色等等。这则小技巧</p>
<p>就是告诉你如何判断一个文件是否在Internet Explorer的缓存中，以满足你的须要。</p>
<p>　　新建一个项目、添加一个模块。将以下代码写到模块里：</p>
<p></p>
<p>Private Const ERROR_INSUFFICIENT_BUFFER = 122</p>
<p>Private Const eeErrorBase = 26720</p>
<p></p>
<p>Private Type FILETIME</p>
<p>　 dwLowDateTime As Long</p>
<p>　 dwHighDateTime As Long</p>
<p>End Type</p>
<p></p>
<p>Private Type INTERNET_CACHE_ENTRY_INFO</p>
<p>　 dwStructSize As Long</p>
<p>　 lpszSourceUrlName As String</p>
<p>　 lpszLocalFileName As String</p>
<p>　 CacheEntryType As String</p>
<p>　 dwUseCount As Long</p>
<p>　 dwHitRate As Long</p>
<p>　 dwSizeLow As Long</p>
<p>　 dwSizeHigh As Long</p>
<p>　 LastModifiedTime As FILETIME</p>
<p>　 ExpireTIme As FILETIME</p>
<p>　 LastAccessTime As FILETIME</p>
<p>　 LastSyncTime As FILETIME</p>
<p>　 lpHeaderInfo As Long</p>
<p>　 dwHeaderInfoSize As Long</p>
<p>　 lpszFileExtension As String</p>
<p>　 dwReserved As Long</p>
<p>End Type</p>
<p></p>
<p>Private Declare Function GetUrlCacheEntryInfo Lib "wininet.dll" _</p>
<p>Alias "GetUrlCacheEntryInfoA" (ByVal sUrlName As String, _</p>
<p>　 lpCacheEntryInfo As Any, lpdwCacheEntryInfoBufferSize _</p>
<p>　 As Long) As Long</p>
<p></p>
<p>注释：用来报告API产生的错误：</p>
<p>Private Const FORMAT_MESSAGE_ALLOCATE_BUFFER = &H100</p>
<p>Private Const FORMAT_MESSAGE_ARGUMENT_ARRAY = &H2000</p>
<p>Private Const FORMAT_MESSAGE_FROM_HMODULE = &H800</p>
<p>Private Const FORMAT_MESSAGE_FROM_STRING = &H400</p>
<p>Private Const FORMAT_MESSAGE_FROM_SYSTEM = &H1000</p>
<p>Private Const FORMAT_MESSAGE_IGNORE_INSERTS = &H200</p>
<p>Private Const FORMAT_MESSAGE_MAX_WIDTH_MASK = &HFF</p>
<p>Private Declare Function FormatMessage Lib "kernel32" Alias _</p>
<p>　 "FormatMessageA" (ByVal dwFlags As Long, lpSource As Any, _</p>
<p>　 ByVal dwMessageId As Long, ByVal dwLanguageId As Long, _</p>
<p>　 ByVal lpBuffer As String, ByVal nSize As Long, Arguments _</p>
<p>　 As Long) As Long</p>
<p></p>
<p>Public Function WinAPIError(ByVal lLastDLLError As Long) As String</p>
<p>Dim sBuff As String</p>
<p>Dim lCount As Long</p>
<p></p>
<p>　 注释：返回与LastDLLError相关的出错信息：</p>
<p>　 sBuff = String$(256, 0)</p>
<p>　 lCount = FormatMessage( _</p>
<p>　　　FORMAT_MESSAGE_FROM_SYSTEM Or FORMAT_MESSAGE_IGNORE_INSERTS, _</p>
<p>　　　0, lLastDLLError, 0&, sBuff, Len(sBuff), ByVal 0)</p>
<p>　 If lCount Then</p>
<p>　　　WinAPIError = Left$(sBuff, lCount)</p>
<p>　 End If</p>
<p></p>
<p>End Function</p>
<p></p>
<p>Public Function GetCacheEntryInfo(ByVal hWnd As Long, _</p>
<p>　 ByVal lpszUrl As String) As Boolean</p>
<p></p>
<p>Dim dwEntrySize As Long</p>
<p>Dim lpCacheEntry As INTERNET_CACHE_ENTRY_INFO</p>
<p>Dim dwTemp As Long</p>
<p>Dim lErr As Long</p>
<p></p>
<p>　 If (GetUrlCacheEntryInfo(lpszUrl, ByVal 0&, dwEntrySize)) = 0 Then</p>
<p>　　　lErr = Err.LastDllError</p>
<p>　　　If (lErr <> ERROR_INSUFFICIENT_BUFFER) Then</p>
<p>　　　　 注释：预料外的错误。须要显示出错原因：</p>
<p>　　　　 Err.Raise eeErrorBase + 1, _</p>
<p>　　　　　　App.EXEName & ".mCacheEntry", WinAPIError(lErr)</p>
<p></p>
<p>　　　　 GetCacheEntryInfo = False</p>
<p>　　　　 Exit Function</p>
<p>　　　Else</p>
<p>　　　　 注释：这是预料中的错误</p>
<p>　　　　 GetCacheEntryInfo = True</p>
<p>　　　End If</p>
<p>　 End If</p>
<p></p>
<p>End Function</p>
<p></p>
<p></p>
<p>在窗体上添加一个Command和一个Text。然后加入这些代码：</p>
<p></p>
<p>Option Explicit </p>
<p></p>
<p>Private Sub Command1_Click() </p>
<p>On Error Goto ErrorHandler</p>
<p>　 注释：检查Text中的URL地址是否出现在缓存中：</p>
<p>　 If (GetCacheEntryInfo(Me.hWnd, Text1.Text)) Then</p>
<p>　　　MsgBox "URL In Cache.", vbInformation</p>
<p>　 Else</p>
<p>　　　MsgBox "URL Not In Cache.", vbInformation</p>
<p>　 End If</p>
<p></p>
<p>Exit Sub</p>
<p></p>
<p>ErrorHandler:</p>
<p>　MsgBox "URL Not in Cache [" & Err.Description & "]",vbInformation</p>
<p></p>
<p>End Sub</p>
<p></p>
<p>　　运行，在Text中键入一个URL地址（比如，http://www.vbaccelerator.com/index.html）当你按下Command按钮时，就会得到一则消息报告URL在不在缓存中。如果Windows给出了URL没找到的原因，它将被显示在随后的的方括号内。  </p>